Rename markdown to markdown-language-features

2025-12-24 12:19:20 +00:00 · 2018-03-19 21:08:39 -07:00
parent 17faeb913d
commit 468dc867cd
66 changed files with 26 additions and 26 deletions
--- a/extensions/markdown-language-features/.vscodeignore
+++ b/extensions/markdown-language-features/.vscodeignore
@@ -0,0 +1,3 @@
+test/**
+src/**
+tsconfig.json
--- a/extensions/markdown-language-features/OSSREADME.json
+++ b/extensions/markdown-language-features/OSSREADME.json
@@ -0,0 +1,38 @@
+// ATTENTION - THIS DIRECTORY CONTAINS THIRD PARTY OPEN SOURCE MATERIALS:
+[
+{
+	"name": "chriskempson/tomorrow-theme",
+	"version": "0.0.0",
+	"license": "MIT",
+	"repositoryURL": "https://github.com/chriskempson/tomorrow-theme",
+	"licenseDetail": [
+		"Copyright (C) 2013 Chris Kempson",
+		"",
+		"Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the \"Software\"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense,", "and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:",
+		"",
+		"The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.",
+		"",
+		"THE SOFTWARE IS PROVIDED \"AS IS\", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER", "LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE."
+	]
+},
+{
+	"name": "textmate/markdown.tmbundle",
+	"version": "0.0.0",
+	"license": "TextMate Bundle License",
+	"repositoryURL": "https://github.com/textmate/markdown.tmbundle",
+	"licenseDetail": [
+		"Copyright (c) markdown.tmbundle authors",
+		"",
+		"If not otherwise specified (see below), files in this repository fall under the following license:",
+		"",
+		"Permission to copy, use, modify, sell and distribute this",
+		"software is granted. This software is provided \"as is\" without",
+		"express or implied warranty, and with no claim as to its",
+		"suitability for any purpose.",
+		"",
+		"An exception is made for files in readable text which contain their own license information,",
+		"or files where an accompanying file exists (in the same directory) with a \"-license\" suffix added",
+		"to the base-name name of the original file, and an extension of txt, html, or similar. For example",
+		"\"tidy\" is accompanied by \"tidy-license.txt\"."
+	]
+}]
--- a/extensions/markdown-language-features/icon.png
+++ b/extensions/markdown-language-features/icon.png
--- a/extensions/markdown-language-features/media/Preview.svg
+++ b/extensions/markdown-language-features/media/Preview.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 16 16"><style>.st0{fill:#f6f6f6}.st1{fill:none}.st2{fill:#424242}.st3{fill:#f0eff1}</style><path class="st0" d="M11.949 4C11.697 1.756 9.811 0 7.5 0A4.505 4.505 0 0 0 3 4.5c0 .6.12 1.188.35 1.735L0 9.586v.828l2 2 3-2.999V16h11V4h-4.051z" id="outline" style="display: none;"/><g id="icon_x5F_bg"><circle class="st1" cx="7.5" cy="4.5" r="2.5"/><path class="st2" d="M12 10h1v3h-1zM10 11h1v2h-1zM8 12h1v1H8zM8 9h2v1H8z"/><path class="st2" d="M11.949 5a4.431 4.431 0 0 1-.226 1H14v8H7V8.95a4.447 4.447 0 0 1-1-.227V15h9V5h-3.051z"/><path class="st2" d="M10.294 8H12V7h-.762a4.527 4.527 0 0 1-.944 1zM11 4.5a3.5 3.5 0 1 0-7 0c0 .711.215 1.369.579 1.922L1 10l1 1 3.579-3.578A3.485 3.485 0 0 0 7.5 8 3.5 3.5 0 0 0 11 4.5zm-6 0a2.5 2.5 0 1 1 5 0 2.5 2.5 0 0 1-5 0z"/></g><g id="icon_x5F_fg"><path class="st1" d="M10 11h1v2h-1zM8 12h1v1H8zM8 9h2v1H8zM12 10h1v3h-1z"/><path class="st3" d="M11.724 6a4.469 4.469 0 0 1-.485 1H12v1h-1.706c-.771.616-1.733 1-2.794 1-.169 0-.333-.031-.5-.05V14h7V6h-2.276zM8 9h2v1H8V9zm1 4H8v-1h1v1zm2 0h-1v-2h1v2zm2 0h-1v-3h1v3z"/><circle class="st3" cx="7.5" cy="4.5" r="2.5"/></g></svg>
--- a/extensions/markdown-language-features/media/PreviewOnRightPane_16x.svg
+++ b/extensions/markdown-language-features/media/PreviewOnRightPane_16x.svg
@@ -0,0 +1,19 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Generator: Adobe Illustrator 19.2.0, SVG Export Plug-In . SVG Version: 6.00 Build 0)  -->
+<svg version="1.1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" x="0px" y="0px"
+	 viewBox="0 0 16 16" style="enable-background:new 0 0 16 16;" xml:space="preserve">
+<style type="text/css">
+	.icon_x002D_vs_x002D_bg{fill:#424242;}
+</style>
+<g id="canvas">
+</g>
+<g id="outline">
+</g>
+<g id="iconFg">
+</g>
+<g id="iconBg">
+	<path class="icon_x002D_vs_x002D_bg" d="M9,5h5v2.4c0.4,0.2,0.7,0.4,1,0.7V2H1v12h5.6L9,11.6V5z M2,13V5h5v8H2z M11.3,12.7
+		c0.4,0.2,0.8,0.3,1.2,0.3c1.4,0,2.5-1.1,2.5-2.5C15,9.1,13.9,8,12.5,8C11.1,8,10,9.1,10,10.5c0,0.4,0.1,0.8,0.3,1.2L8,14l1,1
+		L11.3,12.7z M11,10.5C11,9.7,11.7,9,12.5,9c0.8,0,1.5,0.7,1.5,1.5c0,0.8-0.7,1.5-1.5,1.5C11.7,12,11,11.3,11,10.5z"/>
+</g>
+</svg>
--- a/extensions/markdown-language-features/media/PreviewOnRightPane_16x_dark.svg
+++ b/extensions/markdown-language-features/media/PreviewOnRightPane_16x_dark.svg
@@ -0,0 +1,19 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Generator: Adobe Illustrator 19.2.0, SVG Export Plug-In . SVG Version: 6.00 Build 0)  -->
+<svg version="1.1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" x="0px" y="0px"
+	 viewBox="0 0 16 16" style="enable-background:new 0 0 16 16;" xml:space="preserve">
+<style type="text/css">
+	.st0{fill:#C5C5C5;}
+</style>
+<g id="canvas">
+</g>
+<g id="outline">
+</g>
+<g id="iconFg">
+</g>
+<g id="iconBg">
+	<path class="st0" d="M9,5h5v2.4c0.4,0.2,0.7,0.4,1,0.7V2H1v12h5.6L9,11.6V5z M2,13V5h5v8H2z M11.3,12.7c0.4,0.2,0.8,0.3,1.2,0.3
+		c1.4,0,2.5-1.1,2.5-2.5C15,9.1,13.9,8,12.5,8C11.1,8,10,9.1,10,10.5c0,0.4,0.1,0.8,0.3,1.2L8,14l1,1L11.3,12.7z M11,10.5
+		C11,9.7,11.7,9,12.5,9c0.8,0,1.5,0.7,1.5,1.5c0,0.8-0.7,1.5-1.5,1.5C11.7,12,11,11.3,11,10.5z"/>
+</g>
+</svg>
--- a/extensions/markdown-language-features/media/Preview_inverse.svg
+++ b/extensions/markdown-language-features/media/Preview_inverse.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 16 16"><style>.st0{fill:#2d2d30}.st1{fill:none}.st2{fill:#c5c5c5}.st3{fill:#2b282e}</style><path class="st0" d="M11.949 4C11.697 1.756 9.811 0 7.5 0A4.505 4.505 0 0 0 3 4.5c0 .6.12 1.188.35 1.735L0 9.586v.828l2 2 3-2.999V16h11V4h-4.051z" id="outline" style="display: none;"/><g id="icon_x5F_bg"><circle class="st1" cx="7.5" cy="4.5" r="2.5"/><path class="st2" d="M12 10h1v3h-1zM10 11h1v2h-1zM8 12h1v1H8zM8 9h2v1H8z"/><path class="st2" d="M11.949 5a4.431 4.431 0 0 1-.226 1H14v8H7V8.95a4.447 4.447 0 0 1-1-.227V15h9V5h-3.051z"/><path class="st2" d="M10.294 8H12V7h-.762a4.527 4.527 0 0 1-.944 1zM11 4.5a3.5 3.5 0 1 0-7 0c0 .711.215 1.369.579 1.922L1 10l1 1 3.579-3.578A3.485 3.485 0 0 0 7.5 8 3.5 3.5 0 0 0 11 4.5zm-6 0a2.5 2.5 0 1 1 5 0 2.5 2.5 0 0 1-5 0z"/></g><g id="icon_x5F_fg"><path class="st1" d="M10 11h1v2h-1zM8 12h1v1H8zM8 9h2v1H8zM12 10h1v3h-1z"/><path class="st3" d="M11.724 6a4.469 4.469 0 0 1-.485 1H12v1h-1.706c-.771.616-1.733 1-2.794 1-.169 0-.333-.031-.5-.05V14h7V6h-2.276zM8 9h2v1H8V9zm1 4H8v-1h1v1zm2 0h-1v-2h1v2zm2 0h-1v-3h1v3z"/><circle class="st3" cx="7.5" cy="4.5" r="2.5"/></g></svg>
--- a/extensions/markdown-language-features/media/ViewSource.svg
+++ b/extensions/markdown-language-features/media/ViewSource.svg
@@ -0,0 +1,3 @@
+<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd" [
+	<!ENTITY ns_flows "http://ns.adobe.com/Flows/1.0/">
+]><svg xmlns="http://www.w3.org/2000/svg" width="16" height="16"><polygon fill="#656565" points="10,2 7.414,2 8.414,3 9,3 9,3.586 9,4 9,4.414 9,6 12,6 12,13 4,13 4,8 3,8 3,14 13,14 13,5"/><polygon fill="#00539C" points="5,1 3,1 5,3 1,3 1,5 5,5 3,7 5,7 8,4"/></svg>
--- a/extensions/markdown-language-features/media/ViewSource_inverse.svg
+++ b/extensions/markdown-language-features/media/ViewSource_inverse.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="16" height="16"><polygon fill="#C5C5C5" points="10,2 7.414,2 8.414,3 9,3 9,3.586 9,4 9,4.414 9,6 12,6 12,13 4,13 4,8 3,8 3,14 13,14 13,5"/><polygon fill="#75BEFF" points="5,1 3,1 5,3 1,3 1,5 5,5 3,7 5,7 8,4"/></svg>
--- a/extensions/markdown-language-features/media/index.js
+++ b/extensions/markdown-language-features/media/index.js
--- a/extensions/markdown-language-features/media/markdown.css
+++ b/extensions/markdown-language-features/media/markdown.css
@@ -0,0 +1,266 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+body {
+	font-family: "Segoe WPC", "Segoe UI", "SFUIText-Light", "HelveticaNeue-Light", sans-serif, "Droid Sans Fallback";
+	font-size: 14px;
+	padding: 0 26px;
+	line-height: 22px;
+	word-wrap: break-word;
+}
+
+#code-csp-warning {
+	position: fixed;
+	top: 0;
+	right: 0;
+	color: white;
+	margin: 16px;
+	text-align: center;
+	font-size: 12px;
+	font-family: sans-serif;
+	background-color:#444444;
+	cursor: pointer;
+	padding: 6px;
+	box-shadow: 1px 1px 1px rgba(0,0,0,.25);
+}
+
+#code-csp-warning:hover {
+	text-decoration: none;
+	background-color:#007acc;
+	box-shadow: 2px 2px 2px rgba(0,0,0,.25);
+}
+
+
+body.scrollBeyondLastLine {
+	margin-bottom: calc(100vh - 22px);
+}
+
+body.showEditorSelection .code-line {
+	position: relative;
+}
+
+body.showEditorSelection .code-active-line:before,
+body.showEditorSelection .code-line:hover:before {
+	content: "";
+	display: block;
+	position: absolute;
+	top: 0;
+	left: -12px;
+	height: 100%;
+}
+
+body.showEditorSelection li.code-active-line:before,
+body.showEditorSelection li.code-line:hover:before {
+	left: -30px;
+}
+
+.vscode-light.showEditorSelection .code-active-line:before {
+	border-left: 3px solid rgba(0, 0, 0, 0.15);
+}
+
+.vscode-light.showEditorSelection .code-line:hover:before {
+	border-left: 3px solid rgba(0, 0, 0, 0.40);
+}
+
+.vscode-light.showEditorSelection .code-line .code-line:hover:before {
+	border-left: none;
+}
+
+.vscode-dark.showEditorSelection .code-active-line:before {
+	border-left: 3px solid rgba(255, 255, 255, 0.4);
+}
+
+.vscode-dark.showEditorSelection .code-line:hover:before {
+	border-left: 3px solid rgba(255, 255, 255, 0.60);
+}
+
+.vscode-dark.showEditorSelection .code-line .code-line:hover:before {
+	border-left: none;
+}
+
+.vscode-high-contrast.showEditorSelection .code-active-line:before {
+	border-left: 3px solid rgba(255, 160, 0, 0.7);
+}
+
+.vscode-high-contrast.showEditorSelection .code-line:hover:before {
+	border-left: 3px solid rgba(255, 160, 0, 1);
+}
+
+.vscode-high-contrast.showEditorSelection .code-line .code-line:hover:before {
+	border-left: none;
+}
+
+img {
+	max-width: 100%;
+	max-height: 100%;
+}
+
+a {
+	color: #4080D0;
+	text-decoration: none;
+}
+
+a:focus,
+input:focus,
+select:focus,
+textarea:focus {
+	outline: 1px solid -webkit-focus-ring-color;
+	outline-offset: -1px;
+}
+
+hr {
+	border: 0;
+	height: 2px;
+	border-bottom: 2px solid;
+}
+
+h1 {
+	padding-bottom: 0.3em;
+	line-height: 1.2;
+	border-bottom-width: 1px;
+	border-bottom-style: solid;
+}
+
+h1, h2, h3 {
+	font-weight: normal;
+}
+
+h1 code,
+h2 code,
+h3 code,
+h4 code,
+h5 code,
+h6 code {
+	font-size: inherit;
+	line-height: auto;
+}
+
+a:hover {
+	color: #4080D0;
+	text-decoration: underline;
+}
+
+table {
+	border-collapse: collapse;
+}
+
+table > thead > tr > th {
+	text-align: left;
+	border-bottom: 1px solid;
+}
+
+table > thead > tr > th,
+table > thead > tr > td,
+table > tbody > tr > th,
+table > tbody > tr > td {
+	padding: 5px 10px;
+}
+
+table > tbody > tr + tr > td {
+	border-top: 1px solid;
+}
+
+blockquote {
+	margin: 0 7px 0 5px;
+	padding: 0 16px 0 10px;
+	border-left: 5px solid;
+}
+
+code {
+	font-family: Menlo, Monaco, Consolas, "Droid Sans Mono", "Courier New", monospace, "Droid Sans Fallback";
+	font-size: 14px;
+	line-height: 19px;
+}
+
+body.wordWrap pre {
+	white-space: pre-wrap;
+}
+
+.mac code {
+	font-size: 12px;
+	line-height: 18px;
+}
+
+pre:not(.hljs),
+pre.hljs code > div {
+	padding: 16px;
+	border-radius: 3px;
+	overflow: auto;
+}
+
+/** Theming */
+
+.vscode-light,
+.vscode-light pre code {
+	color: rgb(30, 30, 30);
+}
+
+.vscode-dark,
+.vscode-dark pre code {
+	color: #DDD;
+}
+
+.vscode-high-contrast,
+.vscode-high-contrast pre code {
+	color: white;
+}
+
+.vscode-light code {
+	color: #A31515;
+}
+
+.vscode-dark code {
+	color: #D7BA7D;
+}
+
+.vscode-light pre:not(.hljs),
+.vscode-light code > div {
+	background-color: rgba(220, 220, 220, 0.4);
+}
+
+.vscode-dark pre:not(.hljs),
+.vscode-dark code > div {
+	background-color: rgba(10, 10, 10, 0.4);
+}
+
+.vscode-high-contrast pre:not(.hljs),
+.vscode-high-contrast code > div {
+	background-color: rgb(0, 0, 0);
+}
+
+.vscode-high-contrast h1 {
+	border-color: rgb(0, 0, 0);
+}
+
+.vscode-light table > thead > tr > th {
+	border-color: rgba(0, 0, 0, 0.69);
+}
+
+.vscode-dark table > thead > tr > th {
+	border-color: rgba(255, 255, 255, 0.69);
+}
+
+.vscode-light h1,
+.vscode-light hr,
+.vscode-light table > tbody > tr + tr > td {
+	border-color: rgba(0, 0, 0, 0.18);
+}
+
+.vscode-dark h1,
+.vscode-dark hr,
+.vscode-dark table > tbody > tr + tr > td {
+	border-color: rgba(255, 255, 255, 0.18);
+}
+
+.vscode-light blockquote,
+.vscode-dark blockquote {
+	background: rgba(127, 127, 127, 0.1);
+	border-color: rgba(0, 122, 204, 0.5);
+}
+
+.vscode-high-contrast blockquote {
+	background: transparent;
+	border-color: #fff;
+}
--- a/extensions/markdown-language-features/media/pre.js
+++ b/extensions/markdown-language-features/media/pre.js
--- a/extensions/markdown-language-features/media/tomorrow.css
+++ b/extensions/markdown-language-features/media/tomorrow.css
@@ -0,0 +1,73 @@
+/* Tomorrow Theme */
+/* http://jmblog.github.com/color-themes-for-google-code-highlightjs */
+/* Original theme - https://github.com/chriskempson/tomorrow-theme */
+
+/* Tomorrow Comment */
+.hljs-comment,
+.hljs-quote {
+	color: #8e908c;
+}
+
+/* Tomorrow Red */
+.hljs-variable,
+.hljs-template-variable,
+.hljs-tag,
+.hljs-name,
+.hljs-selector-id,
+.hljs-selector-class,
+.hljs-regexp,
+.hljs-deletion {
+	color: #c82829;
+}
+
+/* Tomorrow Orange */
+.hljs-number,
+.hljs-built_in,
+.hljs-builtin-name,
+.hljs-literal,
+.hljs-type,
+.hljs-params,
+.hljs-meta,
+.hljs-link {
+	color: #f5871f;
+}
+
+/* Tomorrow Yellow */
+.hljs-attribute {
+	color: #eab700;
+}
+
+/* Tomorrow Green */
+.hljs-string,
+.hljs-symbol,
+.hljs-bullet,
+.hljs-addition {
+	color: #718c00;
+}
+
+/* Tomorrow Blue */
+.hljs-title,
+.hljs-section {
+	color: #4271ae;
+}
+
+/* Tomorrow Purple */
+.hljs-keyword,
+.hljs-selector-tag {
+	color: #8959a8;
+}
+
+.hljs {
+	display: block;
+	overflow-x: auto;
+	color: #4d4d4c;
+	padding: 0.5em;
+}
+
+.hljs-emphasis {
+	font-style: italic;
+}
+
+.hljs-strong {
+	font-weight: bold;
+}
--- a/extensions/markdown-language-features/package-lock.json
+++ b/extensions/markdown-language-features/package-lock.json
--- a/extensions/markdown-language-features/package.json
+++ b/extensions/markdown-language-features/package.json
@@ -0,0 +1,305 @@
+{
+	"name": "markdown-language-features",
+	"displayName": "%displayName%",
+	"description": "%description%",
+	"version": "1.0.0",
+	"icon": "icon.png",
+	"publisher": "vscode",
+	"aiKey": "AIF-d9b70cd4-b9f9-4d70-929b-a071c400b217",
+	"enableProposedApi": true,
+	"engines": {
+		"vscode": "^1.20.0"
+	},
+	"main": "./out/extension",
+	"categories": [
+		"Languages"
+	],
+	"activationEvents": [
+		"onLanguage:markdown",
+		"onCommand:markdown.preview.toggleLock",
+		"onCommand:markdown.preview.refresh",
+		"onCommand:markdown.showPreview",
+		"onCommand:markdown.showPreviewToSide",
+		"onCommand:markdown.showLockedPreviewToSide",
+		"onCommand:markdown.showSource",
+		"onCommand:markdown.showPreviewSecuritySelector"
+	],
+	"contributes": {
+		"commands": [
+			{
+				"command": "markdown.showPreview",
+				"title": "%markdown.preview.title%",
+				"category": "Markdown",
+				"icon": {
+					"light": "./media/Preview.svg",
+					"dark": "./media/Preview_inverse.svg"
+				}
+			},
+			{
+				"command": "markdown.showPreviewToSide",
+				"title": "%markdown.previewSide.title%",
+				"category": "Markdown",
+				"icon": {
+					"light": "./media/PreviewOnRightPane_16x.svg",
+					"dark": "./media/PreviewOnRightPane_16x_dark.svg"
+				}
+			},
+			{
+				"command": "markdown.showLockedPreviewToSide",
+				"title": "%markdown.showLockedPreviewToSide.title%",
+				"category": "Markdown",
+				"icon": {
+					"light": "./media/PreviewOnRightPane_16x.svg",
+					"dark": "./media/PreviewOnRightPane_16x_dark.svg"
+				}
+			},
+			{
+				"command": "markdown.showSource",
+				"title": "%markdown.showSource.title%",
+				"category": "Markdown",
+				"icon": {
+					"light": "./media/ViewSource.svg",
+					"dark": "./media/ViewSource_inverse.svg"
+				}
+			},
+			{
+				"command": "markdown.showPreviewSecuritySelector",
+				"title": "%markdown.showPreviewSecuritySelector.title%",
+				"category": "Markdown"
+			},
+			{
+				"command": "markdown.preview.refresh",
+				"title": "%markdown.preview.refresh.title%",
+				"category": "Markdown"
+			},
+			{
+				"command": "markdown.preview.toggleLock",
+				"title": "%markdown.preview.toggleLock.title%",
+				"category": "Markdown"
+			}
+		],
+		"menus": {
+			"editor/title": [
+				{
+					"command": "markdown.showPreviewToSide",
+					"when": "editorLangId == markdown",
+					"alt": "markdown.showPreview",
+					"group": "navigation"
+				},
+				{
+					"command": "markdown.showSource",
+					"when": "markdownPreviewFocus",
+					"group": "navigation"
+				},
+				{
+					"command": "markdown.preview.refresh",
+					"when": "markdownPreviewFocus",
+					"group": "1_markdown"
+				},
+				{
+					"command": "markdown.preview.toggleLock",
+					"when": "markdownPreviewFocus",
+					"group": "1_markdown"
+				},
+				{
+					"command": "markdown.showPreviewSecuritySelector",
+					"when": "markdownPreviewFocus",
+					"group": "1_markdown"
+				}
+			],
+			"explorer/context": [
+				{
+					"command": "markdown.showPreview",
+					"when": "resourceLangId == markdown",
+					"group": "navigation"
+				}
+			],
+			"commandPalette": [
+				{
+					"command": "markdown.showPreview",
+					"when": "editorLangId == markdown",
+					"group": "navigation"
+				},
+				{
+					"command": "markdown.showPreviewToSide",
+					"when": "editorLangId == markdown",
+					"group": "navigation"
+				},
+				{
+					"command": "markdown.showLockedPreviewToSide",
+					"when": "editorLangId == markdown",
+					"group": "navigation"
+				},
+				{
+					"command": "markdown.showSource",
+					"when": "markdownPreviewFocus",
+					"group": "navigation"
+				},
+				{
+					"command": "markdown.showPreviewSecuritySelector",
+					"when": "editorLangId == markdown"
+				},
+				{
+					"command": "markdown.showPreviewSecuritySelector",
+					"when": "markdownPreviewFocus"
+				},
+				{
+					"command": "markdown.preview.toggleLock",
+					"when": "markdownPreviewFocus"
+				}
+			]
+		},
+		"keybindings": [
+			{
+				"command": "markdown.showPreview",
+				"key": "shift+ctrl+v",
+				"mac": "shift+cmd+v",
+				"when": "editorLangId == markdown"
+			},
+			{
+				"command": "markdown.showPreviewToSide",
+				"key": "ctrl+k v",
+				"mac": "cmd+k v",
+				"when": "editorLangId == markdown"
+			}
+		],
+		"configuration": {
+			"type": "object",
+			"title": "Markdown",
+			"order": 20,
+			"properties": {
+				"markdown.styles": {
+					"type": "array",
+					"default": [],
+					"description": "%markdown.styles.dec%",
+					"scope": "resource"
+				},
+				"markdown.previewFrontMatter": {
+					"type": "string",
+					"enum": [
+						"hide",
+						"show"
+					],
+					"default": "hide",
+					"description": "%markdown.previewFrontMatter.dec%",
+					"scope": "resource"
+				},
+				"markdown.preview.breaks": {
+					"type": "boolean",
+					"default": false,
+					"description": "%markdown.preview.breaks.desc%",
+					"scope": "resource"
+				},
+				"markdown.preview.linkify": {
+					"type": "boolean",
+					"default": true,
+					"description": "%markdown.preview.linkify%",
+					"scope": "resource"
+				},
+				"markdown.preview.fontFamily": {
+					"type": "string",
+					"default": "-apple-system, BlinkMacSystemFont, 'Segoe WPC', 'Segoe UI', 'HelveticaNeue-Light', 'Ubuntu', 'Droid Sans', sans-serif",
+					"description": "%markdown.preview.fontFamily.desc%",
+					"scope": "resource"
+				},
+				"markdown.preview.fontSize": {
+					"type": "number",
+					"default": 14,
+					"description": "%markdown.preview.fontSize.desc%",
+					"scope": "resource"
+				},
+				"markdown.preview.lineHeight": {
+					"type": "number",
+					"default": 1.6,
+					"description": "%markdown.preview.lineHeight.desc%",
+					"scope": "resource"
+				},
+				"markdown.preview.scrollPreviewWithEditor": {
+					"type": "boolean",
+					"default": true,
+					"description": "%markdown.preview.scrollPreviewWithEditor.desc%",
+					"scope": "resource"
+				},
+				"markdown.preview.scrollPreviewWithEditorSelection": {
+					"type": "boolean",
+					"default": true,
+					"description": "%markdown.preview.scrollPreviewWithEditorSelection.desc%",
+					"deprecationMessage": "%markdown.preview.scrollPreviewWithEditorSelection.deprecationMessage%"
+				},
+				"markdown.preview.markEditorSelection": {
+					"type": "boolean",
+					"default": true,
+					"description": "%markdown.preview.markEditorSelection.desc%",
+					"scope": "resource"
+				},
+				"markdown.preview.scrollEditorWithPreview": {
+					"type": "boolean",
+					"default": true,
+					"description": "%markdown.preview.scrollEditorWithPreview.desc%",
+					"scope": "resource"
+				},
+				"markdown.preview.doubleClickToSwitchToEditor": {
+					"type": "boolean",
+					"default": true,
+					"description": "%markdown.preview.doubleClickToSwitchToEditor.desc%",
+					"scope": "resource"
+				},
+				"markdown.trace": {
+					"type": "string",
+					"enum": [
+						"off",
+						"verbose"
+					],
+					"default": "off",
+					"description": "%markdown.trace.desc%",
+					"scope": "window"
+				}
+			}
+		},
+		"configurationDefaults": {
+			"[markdown]": {
+				"editor.wordWrap": "on",
+				"editor.quickSuggestions": false
+			}
+		},
+		"jsonValidation": [
+			{
+				"fileMatch": "package.json",
+				"url": "./schemas/package.schema.json"
+			}
+		],
+		"markdown.previewStyles": [
+			"./media/markdown.css",
+			"./media/tomorrow.css"
+		],
+		"markdown.previewScripts": [
+			"./media/index.js"
+		]
+	},
+	"scripts": {
+		"compile": "gulp compile-extension:markdown && npm run build-preview",
+		"watch": "npm run build-preview && gulp watch-extension:markdown",
+		"vscode:prepublish": "npm run build-ext && npm run build-preview",
+		"build-ext": "node ../../node_modules/gulp/bin/gulp.js --gulpfile ../../build/gulpfile.extensions.js compile-extension:markdown ./tsconfig.json",
+		"build-preview": "webpack --mode development"
+	},
+	"dependencies": {
+		"highlight.js": "9.5.0",
+		"markdown-it": "^8.4.0",
+		"markdown-it-named-headers": "0.0.4",
+		"vscode-extension-telemetry": "0.0.15",
+		"vscode-nls": "^3.2.1"
+	},
+	"devDependencies": {
+		"@types/highlight.js": "9.1.10",
+		"@types/lodash.throttle": "^4.1.3",
+		"@types/markdown-it": "0.0.2",
+		"@types/node": "7.0.43",
+		"lodash.throttle": "^4.1.1",
+		"ts-loader": "^4.0.1",
+		"typescript": "^2.7.2",
+		"vscode": "^1.1.10",
+		"webpack": "^4.1.0",
+		"webpack-cli": "^2.0.10"
+	}
+}
--- a/extensions/markdown-language-features/package.nls.json
+++ b/extensions/markdown-language-features/package.nls.json
@@ -0,0 +1,25 @@
+{
+	"displayName": "Markdown Language Features",
+	"description": "Provides rich language support for Markdown.",
+	"markdown.preview.breaks.desc": "Sets how line-breaks are rendered in the markdown preview. Setting it to 'true' creates a <br> for every newline.",
+	"markdown.preview.linkify": "Enable or disable conversion of URL-like text to links in the markdown preview.",
+	"markdown.preview.doubleClickToSwitchToEditor.desc": "Double click in the markdown preview to switch to the editor.",
+	"markdown.preview.fontFamily.desc": "Controls the font family used in the markdown preview.",
+	"markdown.preview.fontSize.desc": "Controls the font size in pixels used in the markdown preview.",
+	"markdown.preview.lineHeight.desc": "Controls the line height used in the markdown preview. This number is relative to the font size.",
+	"markdown.preview.markEditorSelection.desc": "Mark the current editor selection in the markdown preview.",
+	"markdown.preview.scrollEditorWithPreview.desc": "When a markdown preview is scrolled, update the view of the editor.",
+	"markdown.preview.scrollPreviewWithEditor.desc": "When a markdown editor is scrolled, update the view of the preview.",
+	"markdown.preview.scrollPreviewWithEditorSelection.desc": "[Deprecated] Scrolls the markdown preview to reveal the currently selected line from the editor.",
+	"markdown.preview.scrollPreviewWithEditorSelection.deprecationMessage": "This setting has been replaced by 'markdown.preview.scrollPreviewWithEditor' and no longer has any effect.",
+	"markdown.preview.title" : "Open Preview",
+	"markdown.previewFrontMatter.dec": "Sets how YAML front matter should be rendered in the markdown preview. 'hide' removes the front matter. Otherwise, the front matter is treated as markdown content.",
+	"markdown.previewSide.title" : "Open Preview to the Side",
+	"markdown.showLockedPreviewToSide.title": "Open Locked Preview to the Side",
+	"markdown.showSource.title" : "Show Source",
+	"markdown.styles.dec": "A list of URLs or local paths to CSS style sheets to use from the markdown preview. Relative paths are interpreted relative to the folder open in the explorer. If there is no open folder, they are interpreted relative to the location of the markdown file. All '\\' need to be written as '\\\\'.",
+	"markdown.showPreviewSecuritySelector.title": "Change Preview Security Settings",
+	"markdown.trace.desc": "Enable debug logging for the markdown extension.",
+	"markdown.preview.refresh.title": "Refresh Preview",
+	"markdown.preview.toggleLock.title": "Toggle Preview Locking"
+}
--- a/extensions/markdown-language-features/preview-src/activeLineMarker.ts
+++ b/extensions/markdown-language-features/preview-src/activeLineMarker.ts
@@ -0,0 +1,34 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+import { getElementsForSourceLine } from './scroll-sync';
+
+export class ActiveLineMarker {
+	private _current: any;
+
+	onDidChangeTextEditorSelection(line: number) {
+		const { previous } = getElementsForSourceLine(line);
+		this._update(previous && previous.element);
+	}
+
+	_update(before: HTMLElement | undefined) {
+		this._unmarkActiveElement(this._current);
+		this._markActiveElement(before);
+		this._current = before;
+	}
+
+	_unmarkActiveElement(element: HTMLElement | undefined) {
+		if (!element) {
+			return;
+		}
+		element.className = element.className.replace(/\bcode-active-line\b/g, '');
+	}
+
+	_markActiveElement(element: HTMLElement | undefined) {
+		if (!element) {
+			return;
+		}
+		element.className += ' code-active-line';
+	}
+}
--- a/extensions/markdown-language-features/preview-src/csp.ts
+++ b/extensions/markdown-language-features/preview-src/csp.ts
@@ -0,0 +1,49 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import { getSettings } from './settings';
+import { getStrings } from './strings';
+import { postCommand } from './messaging';
+
+/**
+ * Shows an alert when there is a content security policy violation.
+ */
+export class CspAlerter {
+	private didShow = false;
+
+	constructor() {
+		document.addEventListener('securitypolicyviolation', () => {
+			this.showCspWarning();
+		});
+
+		window.addEventListener('message', (event) => {
+			if (event && event.data && event.data.name === 'vscode-did-block-svg') {
+				this.showCspWarning();
+			}
+		});
+	}
+
+	private showCspWarning() {
+		const strings = getStrings();
+		const settings = getSettings();
+
+		if (this.didShow || settings.disableSecurityWarnings) {
+			return;
+		}
+		this.didShow = true;
+
+		const notification = document.createElement('a');
+		notification.innerText = strings.cspAlertMessageText;
+		notification.setAttribute('id', 'code-csp-warning');
+		notification.setAttribute('title', strings.cspAlertMessageTitle);
+
+		notification.setAttribute('role', 'button');
+		notification.setAttribute('aria-label', strings.cspAlertMessageLabel);
+		notification.onclick = () => {
+			postCommand('markdown.showPreviewSecuritySelector', [settings.source]);
+		};
+		document.body.appendChild(notification);
+	}
+}
--- a/extensions/markdown-language-features/preview-src/events.ts
+++ b/extensions/markdown-language-features/preview-src/events.ts
@@ -0,0 +1,12 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+export function onceDocumentLoaded(f: () => void) {
+	if (document.readyState === 'loading' || document.readyState === 'uninitialized') {
+		document.addEventListener('DOMContentLoaded', f);
+	} else {
+		f();
+	}
+}
--- a/extensions/markdown-language-features/preview-src/index.ts
+++ b/extensions/markdown-language-features/preview-src/index.ts
@@ -0,0 +1,117 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import { getSettings } from './settings';
+import { postCommand, postMessage } from './messaging';
+import { onceDocumentLoaded } from './events';
+import { getEditorLineNumberForPageOffset, scrollToRevealSourceLine } from './scroll-sync';
+import { ActiveLineMarker } from './activeLineMarker';
+import throttle = require('lodash.throttle');
+
+var scrollDisabled = true;
+const marker = new ActiveLineMarker();
+const settings = getSettings();
+
+onceDocumentLoaded(() => {
+	if (settings.scrollPreviewWithEditor) {
+		setTimeout(() => {
+			const initialLine = +settings.line;
+			if (!isNaN(initialLine)) {
+				scrollDisabled = true;
+				scrollToRevealSourceLine(initialLine);
+			}
+		}, 0);
+	}
+});
+
+const onUpdateView = (() => {
+	const doScroll = throttle((line: number) => {
+		scrollDisabled = true;
+		scrollToRevealSourceLine(line);
+	}, 50);
+
+	return (line: number, settings: any) => {
+		if (!isNaN(line)) {
+			settings.line = line;
+			doScroll(line);
+		}
+	};
+})();
+
+window.addEventListener('resize', () => {
+	scrollDisabled = true;
+}, true);
+
+window.addEventListener('message', event => {
+	if (event.data.source !== settings.source) {
+		return;
+	}
+
+	switch (event.data.type) {
+		case 'onDidChangeTextEditorSelection':
+			marker.onDidChangeTextEditorSelection(event.data.line);
+			break;
+
+		case 'updateView':
+			onUpdateView(event.data.line, settings);
+			break;
+	}
+}, false);
+
+document.addEventListener('dblclick', event => {
+	if (!settings.doubleClickToSwitchToEditor) {
+		return;
+	}
+
+	// Ignore clicks on links
+	for (let node = event.target as HTMLElement; node; node = node.parentNode as HTMLElement) {
+		if (node.tagName === 'A') {
+			return;
+		}
+	}
+
+	const offset = event.pageY;
+	const line = getEditorLineNumberForPageOffset(offset);
+	if (typeof line === 'number' && !isNaN(line)) {
+		postMessage('didClick', { line });
+	}
+});
+
+document.addEventListener('click', event => {
+	if (!event) {
+		return;
+	}
+
+	let node: any = event.target;
+	while (node) {
+		if (node.tagName && node.tagName === 'A' && node.href) {
+			if (node.getAttribute('href').startsWith('#')) {
+				break;
+			}
+			if (node.href.startsWith('file://') || node.href.startsWith('vscode-resource:')) {
+				const [path, fragment] = node.href.replace(/^(file:\/\/|vscode-resource:)/i, '').split('#');
+				postCommand('_markdown.openDocumentLink', [{ path, fragment }]);
+				event.preventDefault();
+				event.stopPropagation();
+				break;
+			}
+			break;
+		}
+		node = node.parentNode;
+	}
+}, true);
+
+if (settings.scrollEditorWithPreview) {
+	window.addEventListener('scroll', throttle(() => {
+		if (scrollDisabled) {
+			scrollDisabled = false;
+		} else {
+			const line = getEditorLineNumberForPageOffset(window.scrollY);
+			if (typeof line === 'number' && !isNaN(line)) {
+				postMessage('revealLine', { line });
+			}
+		}
+	}, 50));
+}
--- a/extensions/markdown-language-features/preview-src/loading.ts
+++ b/extensions/markdown-language-features/preview-src/loading.ts
@@ -0,0 +1,31 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+import { postCommand } from './messaging';
+
+export class StyleLoadingMonitor {
+	private unloadedStyles: string[] = [];
+
+	constructor() {
+		const onStyleLoadError = (event: any) => {
+			const source = event.target.dataset.source;
+			this.unloadedStyles.push(source);
+		};
+
+		window.addEventListener('DOMContentLoaded', () => {
+			for (const link of document.getElementsByClassName('code-user-style') as HTMLCollectionOf<HTMLElement>) {
+				if (link.dataset.source) {
+					link.onerror = onStyleLoadError;
+				}
+			}
+		});
+
+		window.addEventListener('load', () => {
+			if (!this.unloadedStyles.length) {
+				return;
+			}
+			postCommand('_markdown.onPreviewStyleLoadError', [this.unloadedStyles]);
+		});
+	}
+}
--- a/extensions/markdown-language-features/preview-src/messaging.ts
+++ b/extensions/markdown-language-features/preview-src/messaging.ts
@@ -0,0 +1,24 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import { getSettings } from './settings';
+
+/**
+ * Post a message to the markdown extension
+ */
+export function postMessage(type: string, body: object) {
+	window.parent.postMessage({
+		type,
+		source: getSettings().source,
+		body
+	}, '*');
+}
+
+/**
+ * Post a command to be executed to the markdown extension
+ */
+export function postCommand(command: string, args: any[]) {
+	postMessage('command', { command, args });
+}
--- a/extensions/markdown-language-features/preview-src/pre.ts
+++ b/extensions/markdown-language-features/preview-src/pre.ts
@@ -0,0 +1,13 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import { CspAlerter } from './csp';
+import { StyleLoadingMonitor } from './loading';
+
+// tslint:disable-next-line:no-unused-expression
+new CspAlerter();
+
+// tslint:disable-next-line:no-unused-expression
+new StyleLoadingMonitor();
--- a/extensions/markdown-language-features/preview-src/scroll-sync.ts
+++ b/extensions/markdown-language-features/preview-src/scroll-sync.ts
@@ -0,0 +1,127 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import { getSettings } from './settings';
+
+
+function clamp(min: number, max: number, value: number) {
+	return Math.min(max, Math.max(min, value));
+}
+
+function clampLine(line: number) {
+	return clamp(0, getSettings().lineCount - 1, line);
+}
+
+
+export interface CodeLineElement {
+	element: HTMLElement;
+	line: number;
+}
+
+const getCodeLineElements = (() => {
+	let elements: CodeLineElement[];
+	return () => {
+		if (!elements) {
+			elements = Array.prototype.map.call(
+				document.getElementsByClassName('code-line'),
+				(element: any) => {
+					const line = +element.getAttribute('data-line');
+					return { element, line };
+				})
+				.filter((x: any) => !isNaN(x.line));
+		}
+		return elements;
+	};
+})();
+
+/**
+ * Find the html elements that map to a specific target line in the editor.
+ *
+ * If an exact match, returns a single element. If the line is between elements,
+ * returns the element prior to and the element after the given line.
+ */
+export function getElementsForSourceLine(targetLine: number): { previous: CodeLineElement; next?: CodeLineElement; } {
+	const lineNumber = Math.floor(targetLine);
+	const lines = getCodeLineElements();
+	let previous = lines[0] || null;
+	for (const entry of lines) {
+		if (entry.line === lineNumber) {
+			return { previous: entry, next: undefined };
+		}
+		else if (entry.line > lineNumber) {
+			return { previous, next: entry };
+		}
+		previous = entry;
+	}
+	return { previous };
+}
+
+/**
+ * Find the html elements that are at a specific pixel offset on the page.
+ */
+export function getLineElementsAtPageOffset(offset: number): { previous: CodeLineElement; next?: CodeLineElement; } {
+	const lines = getCodeLineElements();
+	const position = offset - window.scrollY;
+	let lo = -1;
+	let hi = lines.length - 1;
+	while (lo + 1 < hi) {
+		const mid = Math.floor((lo + hi) / 2);
+		const bounds = lines[mid].element.getBoundingClientRect();
+		if (bounds.top + bounds.height >= position) {
+			hi = mid;
+		}
+		else {
+			lo = mid;
+		}
+	}
+	const hiElement = lines[hi];
+	const hiBounds = hiElement.element.getBoundingClientRect();
+	if (hi >= 1 && hiBounds.top > position) {
+		const loElement = lines[lo];
+		return { previous: loElement, next: hiElement };
+	}
+	return { previous: hiElement };
+}
+
+/**
+ * Attempt to reveal the element for a source line in the editor.
+ */
+export function scrollToRevealSourceLine(line: number) {
+	const { previous, next } = getElementsForSourceLine(line);
+	if (previous && getSettings().scrollPreviewWithEditor) {
+		let scrollTo = 0;
+		const rect = previous.element.getBoundingClientRect();
+		const previousTop = rect.top;
+		if (next && next.line !== previous.line) {
+			// Between two elements. Go to percentage offset between them.
+			const betweenProgress = (line - previous.line) / (next.line - previous.line);
+			const elementOffset = next.element.getBoundingClientRect().top - previousTop;
+			scrollTo = previousTop + betweenProgress * elementOffset;
+		}
+		else {
+			scrollTo = previousTop;
+		}
+		window.scroll(0, Math.max(1, window.scrollY + scrollTo));
+	}
+}
+
+export function getEditorLineNumberForPageOffset(offset: number) {
+	const { previous, next } = getLineElementsAtPageOffset(offset);
+	if (previous) {
+		const previousBounds = previous.element.getBoundingClientRect();
+		const offsetFromPrevious = (offset - window.scrollY - previousBounds.top);
+		if (next) {
+			const progressBetweenElements = offsetFromPrevious / (next.element.getBoundingClientRect().top - previousBounds.top);
+			const line = previous.line + progressBetweenElements * (next.line - previous.line);
+			return clampLine(line);
+		}
+		else {
+			const progressWithinElement = offsetFromPrevious / (previousBounds.height);
+			const line = previous.line + progressWithinElement;
+			return clampLine(line);
+		}
+	}
+	return null;
+}
--- a/extensions/markdown-language-features/preview-src/settings.ts
+++ b/extensions/markdown-language-features/preview-src/settings.ts
@@ -0,0 +1,33 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+export interface PreviewSettings {
+	source: string;
+	line: number;
+	lineCount: number;
+	scrollPreviewWithEditor?: boolean;
+	scrollEditorWithPreview: boolean;
+	disableSecurityWarnings: boolean;
+	doubleClickToSwitchToEditor: boolean;
+}
+
+let cachedSettings: PreviewSettings | undefined = undefined;
+
+export function getSettings(): PreviewSettings {
+	if (cachedSettings) {
+		return cachedSettings;
+	}
+
+	const element = document.getElementById('vscode-markdown-preview-data');
+	if (element) {
+		const data = element.getAttribute('data-settings');
+		if (data) {
+			cachedSettings = JSON.parse(data);
+			return cachedSettings!;
+		}
+	}
+
+	throw new Error('Could not load settings');
+}
--- a/extensions/markdown-language-features/preview-src/strings.ts
+++ b/extensions/markdown-language-features/preview-src/strings.ts
@@ -0,0 +1,15 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+export function getStrings(): { [key: string]: string } {
+	const store = document.getElementById('vscode-markdown-preview-data');
+	if (store) {
+		const data = store.getAttribute('data-strings');
+		if (data) {
+			return JSON.parse(data);
+		}
+	}
+	throw new Error('Could not load strings');
+}
--- a/extensions/markdown-language-features/preview-src/tsconfig.json
+++ b/extensions/markdown-language-features/preview-src/tsconfig.json
@@ -0,0 +1,12 @@
+{
+	"compilerOptions": {
+		"outDir": "./dist/",
+		"module": "commonjs",
+		"target": "es6",
+		"jsx": "react",
+		"sourceMap": true,
+		"strict": true,
+		"noImplicitAny": true,
+		"noUnusedLocals": true
+	}
+}
--- a/extensions/markdown-language-features/schemas/package.schema.json
+++ b/extensions/markdown-language-features/schemas/package.schema.json
@@ -0,0 +1,32 @@
+{
+	"$schema": "http://json-schema.org/draft-04/schema#",
+	"title": "Markdown contributions to package.json",
+	"type": "object",
+	"properties": {
+		"contributes": {
+			"type": "object",
+			"properties": {
+				"markdown.previewStyles": {
+					"type": "array",
+					"description": "Contributed CSS files that change the look or layout of the Markdown preview",
+					"items": {
+						"type": "string",
+						"description": "Extension relative path to a css file"
+					}
+				},
+				"markdown.previewScripts": {
+					"type": "array",
+					"description": "Contributed scripts that are executed in the Markdown preview",
+					"items": {
+						"type": "string",
+						"description": "Extension relative path to a JavaScript file"
+					}
+				},
+				"markdown.markdownItPlugins": {
+					"type": "boolean",
+					"description": "Does this extension contribute a markdown-it plugin?"
+				}
+			}
+		}
+	}
+}
--- a/extensions/markdown-language-features/src/commandManager.ts
+++ b/extensions/markdown-language-features/src/commandManager.ts
@@ -0,0 +1,36 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import * as vscode from 'vscode';
+
+export interface Command {
+	readonly id: string;
+
+	execute(...args: any[]): void;
+}
+
+export class CommandManager {
+	private readonly commands = new Map<string, vscode.Disposable>();
+
+	public dispose() {
+		for (const registration of this.commands.values()) {
+			registration.dispose();
+		}
+		this.commands.clear();
+	}
+
+	public register<T extends Command>(command: T): T {
+		this.registerCommand(command.id, command.execute, command);
+		return command;
+	}
+
+	private registerCommand(id: string, impl: (...args: any[]) => void, thisArg?: any) {
+		if (this.commands.has(id)) {
+			return;
+		}
+
+		this.commands.set(id, vscode.commands.registerCommand(id, impl, thisArg));
+	}
+}
--- a/extensions/markdown-language-features/src/commands/index.ts
+++ b/extensions/markdown-language-features/src/commands/index.ts
@@ -0,0 +1,13 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+export { OpenDocumentLinkCommand } from './openDocumentLink';
+export { OnPreviewStyleLoadErrorCommand } from './onPreviewStyleLoadError';
+export { ShowPreviewCommand, ShowPreviewToSideCommand, ShowLockedPreviewToSideCommand } from './showPreview';
+export { ShowSourceCommand } from './showSource';
+export { RefreshPreviewCommand } from './refreshPreview';
+export { ShowPreviewSecuritySelectorCommand } from './showPreviewSecuritySelector';
+export { MoveCursorToPositionCommand } from './moveCursorToPosition';
+export { ToggleLockCommand } from './toggleLock';
--- a/extensions/markdown-language-features/src/commands/moveCursorToPosition.ts
+++ b/extensions/markdown-language-features/src/commands/moveCursorToPosition.ts
@@ -0,0 +1,22 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import * as vscode from 'vscode';
+
+import { Command } from '../commandManager';
+
+export class MoveCursorToPositionCommand implements Command {
+	public readonly id = '_markdown.moveCursorToPosition';
+
+	public execute(line: number, character: number) {
+		if (!vscode.window.activeTextEditor) {
+			return;
+		}
+		const position = new vscode.Position(line, character);
+		const selection = new vscode.Selection(position, position);
+		vscode.window.activeTextEditor.revealRange(selection);
+		vscode.window.activeTextEditor.selection = selection;
+	}
+}
--- a/extensions/markdown-language-features/src/commands/onPreviewStyleLoadError.ts
+++ b/extensions/markdown-language-features/src/commands/onPreviewStyleLoadError.ts
@@ -0,0 +1,18 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+import * as nls from 'vscode-nls';
+const localize = nls.loadMessageBundle();
+
+import * as vscode from 'vscode';
+
+import { Command } from '../commandManager';
+
+export class OnPreviewStyleLoadErrorCommand implements Command {
+	public readonly id = '_markdown.onPreviewStyleLoadError';
+
+	public execute(resources: string[]) {
+		vscode.window.showWarningMessage(localize('onPreviewStyleLoadError', "Could not load 'markdown.styles': {0}", resources.join(', ')));
+	}
+}
--- a/extensions/markdown-language-features/src/commands/openDocumentLink.ts
+++ b/extensions/markdown-language-features/src/commands/openDocumentLink.ts
@@ -0,0 +1,75 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import * as vscode from 'vscode';
+import * as path from 'path';
+
+import { Command } from '../commandManager';
+import { MarkdownEngine } from '../markdownEngine';
+import { TableOfContentsProvider } from '../tableOfContentsProvider';
+import { isMarkdownFile } from '../util/file';
+
+
+export interface OpenDocumentLinkArgs {
+	path: string;
+	fragment: string;
+}
+
+export class OpenDocumentLinkCommand implements Command {
+	private static readonly id = '_markdown.openDocumentLink';
+	public readonly id = OpenDocumentLinkCommand.id;
+
+	public static createCommandUri(
+		path: string,
+		fragment: string
+	): vscode.Uri {
+		return vscode.Uri.parse(`command:${OpenDocumentLinkCommand.id}?${encodeURIComponent(JSON.stringify({ path, fragment }))}`);
+	}
+
+	public constructor(
+		private readonly engine: MarkdownEngine
+	) { }
+
+	public execute(args: OpenDocumentLinkArgs) {
+		const p = decodeURIComponent(args.path);
+		return this.tryOpen(p, args).catch(() => {
+			if (path.extname(p) === '') {
+				return this.tryOpen(p + '.md', args);
+			}
+			const resource = vscode.Uri.file(p);
+			return Promise.resolve(void 0)
+				.then(() => vscode.commands.executeCommand('vscode.open', resource))
+				.then(() => void 0);
+		});
+	}
+
+	private async tryOpen(path: string, args: OpenDocumentLinkArgs) {
+		if (vscode.window.activeTextEditor && isMarkdownFile(vscode.window.activeTextEditor.document) && vscode.window.activeTextEditor.document.uri.fsPath === path) {
+			return this.tryRevealLine(vscode.window.activeTextEditor, args.fragment);
+		} else {
+			const resource = vscode.Uri.file(path);
+			return vscode.workspace.openTextDocument(resource)
+				.then(vscode.window.showTextDocument)
+				.then(editor => this.tryRevealLine(editor, args.fragment));
+		}
+	}
+
+	private async tryRevealLine(editor: vscode.TextEditor, fragment?: string) {
+		if (editor && fragment) {
+			const toc = new TableOfContentsProvider(this.engine, editor.document);
+			const entry = await toc.lookup(fragment);
+			if (entry) {
+				return editor.revealRange(new vscode.Range(entry.line, 0, entry.line, 0), vscode.TextEditorRevealType.AtTop);
+			}
+			const lineNumberFragment = fragment.match(/^L(\d+)$/);
+			if (lineNumberFragment) {
+				const line = +lineNumberFragment[1] - 1;
+				if (!isNaN(line)) {
+					return editor.revealRange(new vscode.Range(line, 0, line, 0), vscode.TextEditorRevealType.AtTop);
+				}
+			}
+		}
+	}
+}
--- a/extensions/markdown-language-features/src/commands/refreshPreview.ts
+++ b/extensions/markdown-language-features/src/commands/refreshPreview.ts
@@ -0,0 +1,19 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import { Command } from '../commandManager';
+import { MarkdownPreviewManager } from '../features/previewManager';
+
+export class RefreshPreviewCommand implements Command {
+	public readonly id = 'markdown.preview.refresh';
+
+	public constructor(
+		private readonly webviewManager: MarkdownPreviewManager
+	) { }
+
+	public execute() {
+		this.webviewManager.refresh();
+	}
+}
--- a/extensions/markdown-language-features/src/commands/showPreview.ts
+++ b/extensions/markdown-language-features/src/commands/showPreview.ts
@@ -0,0 +1,123 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import * as vscode from 'vscode';
+
+import { Command } from '../commandManager';
+import { MarkdownPreviewManager } from '../features/previewManager';
+import { TelemetryReporter } from '../telemetryReporter';
+import { PreviewSettings } from '../features/preview';
+
+
+function getViewColumn(sideBySide: boolean): vscode.ViewColumn | undefined {
+	const active = vscode.window.activeTextEditor;
+	if (!active) {
+		return vscode.ViewColumn.One;
+	}
+
+	if (!sideBySide) {
+		return active.viewColumn;
+	}
+
+	switch (active.viewColumn) {
+		case vscode.ViewColumn.One:
+			return vscode.ViewColumn.Two;
+		case vscode.ViewColumn.Two:
+			return vscode.ViewColumn.Three;
+	}
+
+	return active.viewColumn;
+}
+
+interface ShowPreviewSettings {
+	readonly sideBySide?: boolean;
+	readonly locked?: boolean;
+}
+
+async function showPreview(
+	webviewManager: MarkdownPreviewManager,
+	telemetryReporter: TelemetryReporter,
+	uri: vscode.Uri | undefined,
+	previewSettings: ShowPreviewSettings,
+): Promise<any> {
+	let resource = uri;
+	if (!(resource instanceof vscode.Uri)) {
+		if (vscode.window.activeTextEditor) {
+			// we are relaxed and don't check for markdown files
+			resource = vscode.window.activeTextEditor.document.uri;
+		}
+	}
+
+	if (!(resource instanceof vscode.Uri)) {
+		if (!vscode.window.activeTextEditor) {
+			// this is most likely toggling the preview
+			return vscode.commands.executeCommand('markdown.showSource');
+		}
+		// nothing found that could be shown or toggled
+		return;
+	}
+
+	webviewManager.preview(resource, {
+		resourceColumn: (vscode.window.activeTextEditor && vscode.window.activeTextEditor.viewColumn) || vscode.ViewColumn.One,
+		previewColumn: getViewColumn(!!previewSettings.sideBySide) || vscode.ViewColumn.Active,
+		locked: !!previewSettings.locked
+	});
+
+	telemetryReporter.sendTelemetryEvent('openPreview', {
+		where: previewSettings.sideBySide ? 'sideBySide' : 'inPlace',
+		how: (uri instanceof vscode.Uri) ? 'action' : 'pallete'
+	});
+}
+
+export class ShowPreviewCommand implements Command {
+	public readonly id = 'markdown.showPreview';
+
+	public constructor(
+		private readonly webviewManager: MarkdownPreviewManager,
+		private readonly telemetryReporter: TelemetryReporter
+	) { }
+
+	public execute(mainUri?: vscode.Uri, allUris?: vscode.Uri[], previewSettings?: PreviewSettings) {
+		for (const uri of (allUris || [mainUri])) {
+			showPreview(this.webviewManager, this.telemetryReporter, uri, {
+				sideBySide: false,
+				locked: previewSettings && previewSettings.locked
+			});
+		}
+	}
+}
+
+export class ShowPreviewToSideCommand implements Command {
+	public readonly id = 'markdown.showPreviewToSide';
+
+	public constructor(
+		private readonly webviewManager: MarkdownPreviewManager,
+		private readonly telemetryReporter: TelemetryReporter
+	) { }
+
+	public execute(uri?: vscode.Uri, previewSettings?: PreviewSettings) {
+		showPreview(this.webviewManager, this.telemetryReporter, uri, {
+			sideBySide: true,
+			locked: previewSettings && previewSettings.locked
+		});
+	}
+}
+
+
+export class ShowLockedPreviewToSideCommand implements Command {
+	public readonly id = 'markdown.showLockedPreviewToSide';
+
+	public constructor(
+		private readonly webviewManager: MarkdownPreviewManager,
+		private readonly telemetryReporter: TelemetryReporter
+	) { }
+
+	public execute(uri?: vscode.Uri) {
+		showPreview(this.webviewManager, this.telemetryReporter, uri, {
+			sideBySide: true,
+			locked: true
+		});
+	}
+}
--- a/extensions/markdown-language-features/src/commands/showPreviewSecuritySelector.ts
+++ b/extensions/markdown-language-features/src/commands/showPreviewSecuritySelector.ts
@@ -0,0 +1,30 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import * as vscode from 'vscode';
+import { Command } from '../commandManager';
+import { PreviewSecuritySelector } from '../security';
+import { isMarkdownFile } from '../util/file';
+import { MarkdownPreviewManager } from '../features/previewManager';
+
+export class ShowPreviewSecuritySelectorCommand implements Command {
+	public readonly id = 'markdown.showPreviewSecuritySelector';
+
+	public constructor(
+		private readonly previewSecuritySelector: PreviewSecuritySelector,
+		private readonly previewManager: MarkdownPreviewManager
+	) { }
+
+	public execute(resource: string | undefined) {
+		if (resource) {
+			const source = vscode.Uri.parse(resource).query;
+			this.previewSecuritySelector.showSecutitySelectorForResource(vscode.Uri.parse(source));
+		} else if (vscode.window.activeTextEditor && isMarkdownFile(vscode.window.activeTextEditor.document)) {
+			this.previewSecuritySelector.showSecutitySelectorForResource(vscode.window.activeTextEditor.document.uri);
+		} else if (this.previewManager.activePreviewResource) {
+			this.previewSecuritySelector.showSecutitySelectorForResource(this.previewManager.activePreviewResource);
+		}
+	}
+}
--- a/extensions/markdown-language-features/src/commands/showSource.ts
+++ b/extensions/markdown-language-features/src/commands/showSource.ts
@@ -0,0 +1,30 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import * as vscode from 'vscode';
+import { Command } from '../commandManager';
+import { MarkdownPreviewManager } from '../features/previewManager';
+
+export class ShowSourceCommand implements Command {
+	public readonly id = 'markdown.showSource';
+
+	public constructor(
+		private readonly previewManager: MarkdownPreviewManager
+	) { }
+
+
+	public execute(docUri?: vscode.Uri) {
+		if (!docUri) {
+			return vscode.commands.executeCommand('workbench.action.navigateBack');
+		}
+
+		const resource = this.previewManager.getResourceForPreview(docUri);
+		if (resource) {
+			return vscode.workspace.openTextDocument(resource)
+				.then(document => vscode.window.showTextDocument(document));
+		}
+		return undefined;
+	}
+}
--- a/extensions/markdown-language-features/src/commands/toggleLock.ts
+++ b/extensions/markdown-language-features/src/commands/toggleLock.ts
@@ -0,0 +1,20 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import * as vscode from 'vscode';
+import { Command } from '../commandManager';
+import { MarkdownPreviewManager } from '../features/previewManager';
+
+export class ToggleLockCommand implements Command {
+	public readonly id = 'markdown.preview.toggleLock';
+
+	public constructor(
+		private readonly previewManager: MarkdownPreviewManager
+	) { }
+
+	public execute(previewUri?: vscode.Uri) {
+		this.previewManager.toggleLock(previewUri);
+	}
+}
--- a/extensions/markdown-language-features/src/extension.ts
+++ b/extensions/markdown-language-features/src/extension.ts
@@ -0,0 +1,62 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import * as vscode from 'vscode';
+
+import { MarkdownEngine } from './markdownEngine';
+import { ExtensionContentSecurityPolicyArbiter, PreviewSecuritySelector } from './security';
+import { Logger } from './logger';
+import { CommandManager } from './commandManager';
+import * as commands from './commands/index';
+import { loadDefaultTelemetryReporter } from './telemetryReporter';
+import { getMarkdownExtensionContributions } from './markdownExtensions';
+import LinkProvider from './features/documentLinkProvider';
+import MDDocumentSymbolProvider from './features/documentSymbolProvider';
+import { MarkdownContentProvider } from './features/previewContentProvider';
+import { MarkdownPreviewManager } from './features/previewManager';
+import MarkdownFoldingProvider from './features/foldingProvider';
+
+
+export function activate(context: vscode.ExtensionContext) {
+	const telemetryReporter = loadDefaultTelemetryReporter();
+	context.subscriptions.push(telemetryReporter);
+
+	const contributions = getMarkdownExtensionContributions();
+
+	const cspArbiter = new ExtensionContentSecurityPolicyArbiter(context.globalState, context.workspaceState);
+	const engine = new MarkdownEngine(contributions);
+	const logger = new Logger();
+
+	const selector = 'markdown';
+
+	const contentProvider = new MarkdownContentProvider(engine, context, cspArbiter, contributions, logger);
+
+	const previewManager = new MarkdownPreviewManager(contentProvider, logger, contributions);
+	context.subscriptions.push(previewManager);
+
+	context.subscriptions.push(vscode.languages.registerDocumentSymbolProvider(selector, new MDDocumentSymbolProvider(engine)));
+	context.subscriptions.push(vscode.languages.registerDocumentLinkProvider(selector, new LinkProvider()));
+	context.subscriptions.push(vscode.languages.registerFoldingProvider(selector, new MarkdownFoldingProvider(engine)));
+
+	const previewSecuritySelector = new PreviewSecuritySelector(cspArbiter, previewManager);
+
+	const commandManager = new CommandManager();
+	context.subscriptions.push(commandManager);
+	commandManager.register(new commands.ShowPreviewCommand(previewManager, telemetryReporter));
+	commandManager.register(new commands.ShowPreviewToSideCommand(previewManager, telemetryReporter));
+	commandManager.register(new commands.ShowLockedPreviewToSideCommand(previewManager, telemetryReporter));
+	commandManager.register(new commands.ShowSourceCommand(previewManager));
+	commandManager.register(new commands.RefreshPreviewCommand(previewManager));
+	commandManager.register(new commands.MoveCursorToPositionCommand());
+	commandManager.register(new commands.ShowPreviewSecuritySelectorCommand(previewSecuritySelector, previewManager));
+	commandManager.register(new commands.OnPreviewStyleLoadErrorCommand());
+	commandManager.register(new commands.OpenDocumentLinkCommand(engine));
+	commandManager.register(new commands.ToggleLockCommand(previewManager));
+
+	context.subscriptions.push(vscode.workspace.onDidChangeConfiguration(() => {
+		logger.updateConfiguration();
+		previewManager.updateConfiguration();
+	}));
+}
--- a/extensions/markdown-language-features/src/features/documentLinkProvider.ts
+++ b/extensions/markdown-language-features/src/features/documentLinkProvider.ts
@@ -0,0 +1,158 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import * as vscode from 'vscode';
+import * as path from 'path';
+import { OpenDocumentLinkCommand } from '../commands/openDocumentLink';
+
+function normalizeLink(
+	document: vscode.TextDocument,
+	link: string,
+	base: string
+): vscode.Uri {
+	const uri = vscode.Uri.parse(link);
+	if (uri.scheme) {
+		return uri;
+	}
+
+	// assume it must be a file
+	let resourcePath = uri.path;
+	if (!uri.path) {
+		resourcePath = document.uri.path;
+	} else if (uri.path[0] === '/') {
+		const root = vscode.workspace.getWorkspaceFolder(document.uri);
+		if (root) {
+			resourcePath = path.join(root.uri.fsPath, uri.path);
+		}
+	} else {
+		resourcePath = path.join(base, uri.path);
+	}
+
+	return OpenDocumentLinkCommand.createCommandUri(resourcePath, uri.fragment);
+}
+
+function matchAll(
+	pattern: RegExp,
+	text: string
+): Array<RegExpMatchArray> {
+	const out: RegExpMatchArray[] = [];
+	pattern.lastIndex = 0;
+	let match: RegExpMatchArray | null;
+	while ((match = pattern.exec(text))) {
+		out.push(match);
+	}
+	return out;
+}
+
+export default class LinkProvider implements vscode.DocumentLinkProvider {
+	private readonly linkPattern = /(\[[^\]]*\]\(\s*?)(((((?=.*\)\)+)|(?=.*\)\]+))[^\s\)]+?)|([^\s]+?)))\)/g;
+	private readonly referenceLinkPattern = /(\[([^\]]+)\]\[\s*?)([^\s\]]*?)\]/g;
+	private readonly definitionPattern = /^([\t ]*\[([^\]]+)\]:\s*)(\S+)/gm;
+
+	public provideDocumentLinks(
+		document: vscode.TextDocument,
+		_token: vscode.CancellationToken
+	): vscode.DocumentLink[] {
+		const base = path.dirname(document.uri.fsPath);
+		const text = document.getText();
+
+		return this.providerInlineLinks(text, document, base)
+			.concat(this.provideReferenceLinks(text, document, base));
+	}
+
+	private providerInlineLinks(
+		text: string,
+		document: vscode.TextDocument,
+		base: string
+	): vscode.DocumentLink[] {
+		const results: vscode.DocumentLink[] = [];
+		for (const match of matchAll(this.linkPattern, text)) {
+			const pre = match[1];
+			const link = match[2];
+			const offset = (match.index || 0) + pre.length;
+			const linkStart = document.positionAt(offset);
+			const linkEnd = document.positionAt(offset + link.length);
+			try {
+				results.push(new vscode.DocumentLink(
+					new vscode.Range(linkStart, linkEnd),
+					normalizeLink(document, link, base)));
+			} catch (e) {
+				// noop
+			}
+		}
+
+		return results;
+	}
+
+	private provideReferenceLinks(
+		text: string,
+		document: vscode.TextDocument,
+		base: string
+	): vscode.DocumentLink[] {
+		const results: vscode.DocumentLink[] = [];
+
+		const definitions = this.getDefinitions(text, document);
+		for (const match of matchAll(this.referenceLinkPattern, text)) {
+			let linkStart: vscode.Position;
+			let linkEnd: vscode.Position;
+			let reference = match[3];
+			if (reference) { // [text][ref]
+				const pre = match[1];
+				const offset = (match.index || 0) + pre.length;
+				linkStart = document.positionAt(offset);
+				linkEnd = document.positionAt(offset + reference.length);
+			} else if (match[2]) { // [ref][]
+				reference = match[2];
+				const offset = (match.index || 0) + 1;
+				linkStart = document.positionAt(offset);
+				linkEnd = document.positionAt(offset + match[2].length);
+			} else {
+				continue;
+			}
+
+			try {
+				const link = definitions.get(reference);
+				if (link) {
+					results.push(new vscode.DocumentLink(
+						new vscode.Range(linkStart, linkEnd),
+						vscode.Uri.parse(`command:_markdown.moveCursorToPosition?${encodeURIComponent(JSON.stringify([link.linkRange.start.line, link.linkRange.start.character]))}`)));
+				}
+			} catch (e) {
+				// noop
+			}
+		}
+
+		for (const definition of Array.from(definitions.values())) {
+			try {
+				results.push(new vscode.DocumentLink(
+					definition.linkRange,
+					normalizeLink(document, definition.link, base)));
+			} catch (e) {
+				// noop
+			}
+		}
+
+		return results;
+	}
+
+	private getDefinitions(text: string, document: vscode.TextDocument) {
+		const out = new Map<string, { link: string, linkRange: vscode.Range }>();
+		for (const match of matchAll(this.definitionPattern, text)) {
+			const pre = match[1];
+			const reference = match[2];
+			const link = match[3].trim();
+
+			const offset = (match.index || 0) + pre.length;
+			const linkStart = document.positionAt(offset);
+			const linkEnd = document.positionAt(offset + link.length);
+
+			out.set(reference, {
+				link: link,
+				linkRange: new vscode.Range(linkStart, linkEnd)
+			});
+		}
+		return out;
+	}
+}
--- a/extensions/markdown-language-features/src/features/documentSymbolProvider.ts
+++ b/extensions/markdown-language-features/src/features/documentSymbolProvider.ts
@@ -0,0 +1,23 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import * as vscode from 'vscode';
+
+import { MarkdownEngine } from '../markdownEngine';
+import { TableOfContentsProvider } from '../tableOfContentsProvider';
+
+export default class MDDocumentSymbolProvider implements vscode.DocumentSymbolProvider {
+
+	constructor(
+		private readonly engine: MarkdownEngine
+	) { }
+
+	public async provideDocumentSymbols(document: vscode.TextDocument): Promise<vscode.SymbolInformation[]> {
+		const toc = await new TableOfContentsProvider(this.engine, document).getToc();
+		return toc.map(entry => {
+			return new vscode.SymbolInformation('#'.repeat(entry.level) + ' ' + entry.text, vscode.SymbolKind.Namespace, '', entry.location);
+		});
+	}
+}
--- a/extensions/markdown-language-features/src/features/foldingProvider.ts
+++ b/extensions/markdown-language-features/src/features/foldingProvider.ts
@@ -0,0 +1,48 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import * as vscode from 'vscode';
+
+import { MarkdownEngine } from '../markdownEngine';
+import { TableOfContentsProvider } from '../tableOfContentsProvider';
+
+export default class MarkdownFoldingProvider implements vscode.FoldingProvider {
+
+	constructor(
+		private readonly engine: MarkdownEngine
+	) { }
+
+	public async provideFoldingRanges(
+		document: vscode.TextDocument,
+		context: vscode.FoldingContext,
+		_token: vscode.CancellationToken
+	): Promise<vscode.FoldingRangeList> {
+		const tocProvider = new TableOfContentsProvider(this.engine, document);
+		let toc = await tocProvider.getToc();
+		if (context.maxRanges && toc.length > context.maxRanges) {
+			toc = toc.slice(0, context.maxRanges);
+		}
+
+		const foldingRanges = toc.map((entry, startIndex) => {
+			const start = entry.line;
+			let end: number | undefined = undefined;
+			for (let i = startIndex + 1; i < toc.length; ++i) {
+				if (toc[i].level <= entry.level) {
+					end = toc[i].line - 1;
+					if (document.lineAt(end).isEmptyOrWhitespace && end >= start + 1) {
+						end = end - 1;
+					}
+					break;
+				}
+			}
+			return new vscode.FoldingRange(
+				start,
+				typeof end === 'number' ? end : document.lineCount - 1);
+		});
+
+
+		return new vscode.FoldingRangeList(foldingRanges);
+	}
+}
--- a/extensions/markdown-language-features/src/features/preview.ts
+++ b/extensions/markdown-language-features/src/features/preview.ts
@@ -0,0 +1,304 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import * as vscode from 'vscode';
+import * as path from 'path';
+
+import { Logger } from '../logger';
+import { MarkdownContentProvider } from './previewContentProvider';
+import { disposeAll } from '../util/dispose';
+
+import * as nls from 'vscode-nls';
+import { getVisibleLine, MarkdownFileTopmostLineMonitor } from '../util/topmostLineMonitor';
+import { MarkdownPreviewConfigurationManager } from './previewConfig';
+import { MarkdownContributions } from '../markdownExtensions';
+const localize = nls.loadMessageBundle();
+
+export class MarkdownPreview {
+
+	public static previewScheme = 'vscode-markdown-preview';
+	private static previewCount = 0;
+
+	public readonly uri: vscode.Uri;
+	private readonly webview: vscode.Webview;
+	private throttleTimer: any;
+	private initialLine: number | undefined = undefined;
+	private readonly disposables: vscode.Disposable[] = [];
+	private firstUpdate = true;
+	private currentVersion?: { resource: vscode.Uri, version: number };
+	private forceUpdate = false;
+	private isScrolling = false;
+
+	constructor(
+		private _resource: vscode.Uri,
+		previewColumn: vscode.ViewColumn,
+		public locked: boolean,
+		private readonly contentProvider: MarkdownContentProvider,
+		private readonly previewConfigurations: MarkdownPreviewConfigurationManager,
+		private readonly logger: Logger,
+		topmostLineMonitor: MarkdownFileTopmostLineMonitor,
+		private readonly contributions: MarkdownContributions
+	) {
+		this.uri = vscode.Uri.parse(`${MarkdownPreview.previewScheme}:${MarkdownPreview.previewCount++}`);
+		this.webview = vscode.window.createWebview(
+			this.uri,
+			this.getPreviewTitle(this._resource),
+			previewColumn, {
+				enableScripts: true,
+				enableCommandUris: true,
+				enableFindWidget: true,
+				localResourceRoots: this.getLocalResourceRoots(_resource)
+			});
+
+		this.webview.onDidDispose(() => {
+			this.dispose();
+		}, null, this.disposables);
+
+		this.webview.onDidChangeViewColumn(() => {
+			this._onDidChangeViewColumnEmitter.fire();
+		}, null, this.disposables);
+
+		this.webview.onDidReceiveMessage(e => {
+			if (e.source !== this._resource.toString()) {
+				return;
+			}
+
+			switch (e.type) {
+				case 'command':
+					vscode.commands.executeCommand(e.body.command, ...e.body.args);
+					break;
+
+				case 'revealLine':
+					this.onDidScrollPreview(e.body.line);
+					break;
+
+				case 'didClick':
+					this.onDidClickPreview(e.body.line);
+					break;
+
+			}
+		}, null, this.disposables);
+
+		vscode.workspace.onDidChangeTextDocument(event => {
+			if (this.isPreviewOf(event.document.uri)) {
+				this.refresh();
+			}
+		}, null, this.disposables);
+
+		topmostLineMonitor.onDidChangeTopmostLine(event => {
+			if (this.isPreviewOf(event.resource)) {
+				this.updateForView(event.resource, event.line);
+			}
+		}, null, this.disposables);
+
+		vscode.window.onDidChangeTextEditorSelection(event => {
+			if (this.isPreviewOf(event.textEditor.document.uri)) {
+				this.webview.postMessage({
+					type: 'onDidChangeTextEditorSelection',
+					line: event.selections[0].active.line,
+					source: this.resource.toString()
+				});
+			}
+		}, null, this.disposables);
+	}
+
+	private readonly _onDisposeEmitter = new vscode.EventEmitter<void>();
+	public readonly onDispose = this._onDisposeEmitter.event;
+
+	private readonly _onDidChangeViewColumnEmitter = new vscode.EventEmitter<vscode.ViewColumn>();
+	public readonly onDidChangeViewColumn = this._onDidChangeViewColumnEmitter.event;
+
+	public get resource(): vscode.Uri {
+		return this._resource;
+	}
+
+	public dispose() {
+		this._onDisposeEmitter.fire();
+
+		this._onDisposeEmitter.dispose();
+		this._onDidChangeViewColumnEmitter.dispose();
+		this.webview.dispose();
+
+		disposeAll(this.disposables);
+	}
+
+	public update(resource: vscode.Uri) {
+		const editor = vscode.window.activeTextEditor;
+		if (editor && editor.document.uri.fsPath === resource.fsPath) {
+			this.initialLine = getVisibleLine(editor);
+		} else {
+			this.initialLine = undefined;
+		}
+
+		// If we have changed resources, cancel any pending updates
+		const isResourceChange = resource.fsPath !== this._resource.fsPath;
+		if (isResourceChange) {
+			clearTimeout(this.throttleTimer);
+			this.throttleTimer = undefined;
+		}
+
+		this._resource = resource;
+
+		// Schedule update if none is pending
+		if (!this.throttleTimer) {
+			if (isResourceChange || this.firstUpdate) {
+				this.doUpdate();
+			} else {
+				this.throttleTimer = setTimeout(() => this.doUpdate(), 300);
+			}
+		}
+
+		this.firstUpdate = false;
+	}
+
+	public refresh() {
+		this.forceUpdate = true;
+		this.update(this._resource);
+	}
+
+	public updateConfiguration() {
+		if (this.previewConfigurations.hasConfigurationChanged(this._resource)) {
+			this.refresh();
+		}
+	}
+
+	public get viewColumn(): vscode.ViewColumn | undefined {
+		return this.webview.viewColumn;
+	}
+
+	public isPreviewOf(resource: vscode.Uri): boolean {
+		return this._resource.fsPath === resource.fsPath;
+	}
+
+	public matchesResource(
+		otherResource: vscode.Uri,
+		otherViewColumn: vscode.ViewColumn | undefined,
+		otherLocked: boolean
+	): boolean {
+		if (this.viewColumn !== otherViewColumn) {
+			return false;
+		}
+
+		if (this.locked) {
+			return otherLocked && this.isPreviewOf(otherResource);
+		} else {
+			return !otherLocked;
+		}
+	}
+
+	public matches(otherPreview: MarkdownPreview): boolean {
+		return this.matchesResource(otherPreview._resource, otherPreview.viewColumn, otherPreview.locked);
+	}
+
+	public show(viewColumn: vscode.ViewColumn) {
+		this.webview.show(viewColumn);
+	}
+
+	public toggleLock() {
+		this.locked = !this.locked;
+		this.webview.title = this.getPreviewTitle(this._resource);
+	}
+
+	private getPreviewTitle(resource: vscode.Uri): string {
+		return this.locked
+			? localize('lockedPreviewTitle', '[Preview] {0}', path.basename(resource.fsPath))
+			: localize('previewTitle', 'Preview {0}', path.basename(resource.fsPath));
+	}
+
+	private updateForView(resource: vscode.Uri, topLine: number | undefined) {
+		if (!this.isPreviewOf(resource)) {
+			return;
+		}
+
+		if (this.isScrolling) {
+			this.isScrolling = false;
+			return;
+		}
+
+		if (typeof topLine === 'number') {
+			this.logger.log('updateForView', { markdownFile: resource });
+			this.initialLine = topLine;
+			this.webview.postMessage({
+				type: 'updateView',
+				line: topLine,
+				source: resource.toString()
+			});
+		}
+	}
+
+	private async doUpdate(): Promise<void> {
+		const resource = this._resource;
+
+		clearTimeout(this.throttleTimer);
+		this.throttleTimer = undefined;
+
+		const document = await vscode.workspace.openTextDocument(resource);
+		if (!this.forceUpdate && this.currentVersion && this.currentVersion.resource.fsPath === resource.fsPath && this.currentVersion.version === document.version) {
+			if (this.initialLine) {
+				this.updateForView(resource, this.initialLine);
+			}
+			return;
+		}
+		this.forceUpdate = false;
+
+		this.currentVersion = { resource, version: document.version };
+		this.contentProvider.provideTextDocumentContent(document, this.previewConfigurations, this.initialLine)
+			.then(content => {
+				if (this._resource === resource) {
+					this.webview.title = this.getPreviewTitle(this._resource);
+					this.webview.html = content;
+				}
+			});
+	}
+
+	private getLocalResourceRoots(resource: vscode.Uri): vscode.Uri[] {
+		const baseRoots = this.contributions.previewResourceRoots;
+
+		const folder = vscode.workspace.getWorkspaceFolder(resource);
+		if (folder) {
+			return baseRoots.concat(folder.uri);
+		}
+
+		if (!resource.scheme || resource.scheme === 'file') {
+			return baseRoots.concat(vscode.Uri.file(path.dirname(resource.fsPath)));
+		}
+
+		return baseRoots;
+	}
+
+	private onDidScrollPreview(line: number) {
+		for (const editor of vscode.window.visibleTextEditors) {
+			if (!this.isPreviewOf(editor.document.uri)) {
+				continue;
+			}
+
+			this.isScrolling = true;
+			const sourceLine = Math.floor(line);
+			const fraction = line - sourceLine;
+			const text = editor.document.lineAt(sourceLine).text;
+			const start = Math.floor(fraction * text.length);
+			editor.revealRange(
+				new vscode.Range(sourceLine, start, sourceLine + 1, 0),
+				vscode.TextEditorRevealType.AtTop);
+		}
+	}
+
+	private async onDidClickPreview(line: number): Promise<void> {
+		for (const visibleEditor of vscode.window.visibleTextEditors) {
+			if (this.isPreviewOf(visibleEditor.document.uri)) {
+				const editor = await vscode.window.showTextDocument(visibleEditor.document, visibleEditor.viewColumn);
+				const position = new vscode.Position(line, 0);
+				editor.selection = new vscode.Selection(position, position);
+				return;
+			}
+		}
+	}
+}
+
+export interface PreviewSettings {
+	readonly resourceColumn: vscode.ViewColumn;
+	readonly previewColumn: vscode.ViewColumn;
+	readonly locked: boolean;
+}
--- a/extensions/markdown-language-features/src/features/previewConfig.ts
+++ b/extensions/markdown-language-features/src/features/previewConfig.ts
@@ -0,0 +1,104 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import * as vscode from 'vscode';
+
+export class MarkdownPreviewConfiguration {
+	public static getForResource(resource: vscode.Uri) {
+		return new MarkdownPreviewConfiguration(resource);
+	}
+
+	public readonly scrollBeyondLastLine: boolean;
+	public readonly wordWrap: boolean;
+	public readonly previewFrontMatter: string;
+	public readonly lineBreaks: boolean;
+	public readonly doubleClickToSwitchToEditor: boolean;
+	public readonly scrollEditorWithPreview: boolean;
+	public readonly scrollPreviewWithEditor: boolean;
+	public readonly markEditorSelection: boolean;
+
+	public readonly lineHeight: number;
+	public readonly fontSize: number;
+	public readonly fontFamily: string | undefined;
+	public readonly styles: string[];
+
+	private constructor(resource: vscode.Uri) {
+		const editorConfig = vscode.workspace.getConfiguration('editor', resource);
+		const markdownConfig = vscode.workspace.getConfiguration('markdown', resource);
+		const markdownEditorConfig = vscode.workspace.getConfiguration('[markdown]');
+
+		this.scrollBeyondLastLine = editorConfig.get<boolean>('scrollBeyondLastLine', false);
+
+		this.wordWrap = editorConfig.get<string>('wordWrap', 'off') !== 'off';
+		if (markdownEditorConfig && markdownEditorConfig['editor.wordWrap']) {
+			this.wordWrap = markdownEditorConfig['editor.wordWrap'] !== 'off';
+		}
+
+		this.previewFrontMatter = markdownConfig.get<string>('previewFrontMatter', 'hide');
+		this.scrollPreviewWithEditor = !!markdownConfig.get<boolean>('preview.scrollPreviewWithEditor', true);
+		this.scrollEditorWithPreview = !!markdownConfig.get<boolean>('preview.scrollEditorWithPreview', true);
+		this.lineBreaks = !!markdownConfig.get<boolean>('preview.breaks', false);
+		this.doubleClickToSwitchToEditor = !!markdownConfig.get<boolean>('preview.doubleClickToSwitchToEditor', true);
+		this.markEditorSelection = !!markdownConfig.get<boolean>('preview.markEditorSelection', true);
+
+		this.fontFamily = markdownConfig.get<string | undefined>('preview.fontFamily', undefined);
+		this.fontSize = Math.max(8, +markdownConfig.get<number>('preview.fontSize', NaN));
+		this.lineHeight = Math.max(0.6, +markdownConfig.get<number>('preview.lineHeight', NaN));
+
+		this.styles = markdownConfig.get<string[]>('styles', []);
+	}
+
+	public isEqualTo(otherConfig: MarkdownPreviewConfiguration) {
+		for (let key in this) {
+			if (this.hasOwnProperty(key) && key !== 'styles') {
+				if (this[key] !== otherConfig[key]) {
+					return false;
+				}
+			}
+		}
+
+		// Check styles
+		if (this.styles.length !== otherConfig.styles.length) {
+			return false;
+		}
+		for (let i = 0; i < this.styles.length; ++i) {
+			if (this.styles[i] !== otherConfig.styles[i]) {
+				return false;
+			}
+		}
+
+		return true;
+	}
+
+	[key: string]: any;
+}
+
+export class MarkdownPreviewConfigurationManager {
+	private readonly previewConfigurationsForWorkspaces = new Map<string, MarkdownPreviewConfiguration>();
+
+	public loadAndCacheConfiguration(
+		resource: vscode.Uri
+	): MarkdownPreviewConfiguration {
+		const config = MarkdownPreviewConfiguration.getForResource(resource);
+		this.previewConfigurationsForWorkspaces.set(this.getKey(resource), config);
+		return config;
+	}
+
+	public hasConfigurationChanged(
+		resource: vscode.Uri
+	): boolean {
+		const key = this.getKey(resource);
+		const currentConfig = this.previewConfigurationsForWorkspaces.get(key);
+		const newConfig = MarkdownPreviewConfiguration.getForResource(resource);
+		return (!currentConfig || !currentConfig.isEqualTo(newConfig));
+	}
+
+	private getKey(
+		resource: vscode.Uri
+	): string {
+		const folder = vscode.workspace.getWorkspaceFolder(resource);
+		return folder ? folder.uri.toString() : '';
+	}
+}
--- a/extensions/markdown-language-features/src/features/previewContentProvider.ts
+++ b/extensions/markdown-language-features/src/features/previewContentProvider.ts
@@ -0,0 +1,175 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import * as vscode from 'vscode';
+import * as path from 'path';
+import { MarkdownEngine } from '../markdownEngine';
+
+import * as nls from 'vscode-nls';
+const localize = nls.loadMessageBundle();
+
+import { Logger } from '../logger';
+import { ContentSecurityPolicyArbiter, MarkdownPreviewSecurityLevel } from '../security';
+import { MarkdownPreviewConfigurationManager, MarkdownPreviewConfiguration } from './previewConfig';
+import { MarkdownContributions } from '../markdownExtensions';
+
+/**
+ * Strings used inside the markdown preview.
+ *
+ * Stored here and then injected in the preview so that they
+ * can be localized using our normal localization process.
+ */
+const previewStrings = {
+	cspAlertMessageText: localize(
+		'preview.securityMessage.text',
+		'Some content has been disabled in this document'),
+
+	cspAlertMessageTitle: localize(
+		'preview.securityMessage.title',
+		'Potentially unsafe or insecure content has been disabled in the markdown preview. Change the Markdown preview security setting to allow insecure content or enable scripts'),
+
+	cspAlertMessageLabel: localize(
+		'preview.securityMessage.label',
+		'Content Disabled Security Warning')
+};
+
+export class MarkdownContentProvider {
+	constructor(
+		private readonly engine: MarkdownEngine,
+		private readonly context: vscode.ExtensionContext,
+		private readonly cspArbiter: ContentSecurityPolicyArbiter,
+		private readonly contributions: MarkdownContributions,
+		private readonly logger: Logger
+	) { }
+
+	public async provideTextDocumentContent(
+		markdownDocument: vscode.TextDocument,
+		previewConfigurations: MarkdownPreviewConfigurationManager,
+		initialLine: number | undefined = undefined
+	): Promise<string> {
+		const sourceUri = markdownDocument.uri;
+		const config = previewConfigurations.loadAndCacheConfiguration(sourceUri);
+		const initialData = {
+			source: sourceUri.toString(),
+			line: initialLine,
+			lineCount: markdownDocument.lineCount,
+			scrollPreviewWithEditor: config.scrollPreviewWithEditor,
+			scrollEditorWithPreview: config.scrollEditorWithPreview,
+			doubleClickToSwitchToEditor: config.doubleClickToSwitchToEditor,
+			disableSecurityWarnings: this.cspArbiter.shouldDisableSecurityWarnings()
+		};
+
+		this.logger.log('provideTextDocumentContent', initialData);
+
+		// Content Security Policy
+		const nonce = new Date().getTime() + '' + new Date().getMilliseconds();
+		const csp = this.getCspForResource(sourceUri, nonce);
+
+		const body = await this.engine.render(sourceUri, config.previewFrontMatter === 'hide', markdownDocument.getText());
+		return `<!DOCTYPE html>
+			<html>
+			<head>
+				<meta http-equiv="Content-type" content="text/html;charset=UTF-8">
+				${csp}
+				<meta id="vscode-markdown-preview-data" data-settings="${JSON.stringify(initialData).replace(/"/g, '&quot;')}" data-strings="${JSON.stringify(previewStrings).replace(/"/g, '&quot;')}">
+				<script src="${this.extensionResourcePath('pre.js')}" nonce="${nonce}"></script>
+				${this.getStyles(sourceUri, nonce, config)}
+				<base href="${markdownDocument.uri.with({ scheme: 'vscode-resource' }).toString(true)}">
+			</head>
+			<body class="vscode-body ${config.scrollBeyondLastLine ? 'scrollBeyondLastLine' : ''} ${config.wordWrap ? 'wordWrap' : ''} ${config.markEditorSelection ? 'showEditorSelection' : ''}">
+				${body}
+				<div class="code-line" data-line="${markdownDocument.lineCount}"></div>
+				${this.getScripts(nonce)}
+			</body>
+			</html>`;
+	}
+
+	private extensionResourcePath(mediaFile: string): string {
+		return vscode.Uri.file(this.context.asAbsolutePath(path.join('media', mediaFile)))
+			.with({ scheme: 'vscode-resource' })
+			.toString();
+	}
+
+	private fixHref(resource: vscode.Uri, href: string): string {
+		if (!href) {
+			return href;
+		}
+
+		// Use href if it is already an URL
+		const hrefUri = vscode.Uri.parse(href);
+		if (['http', 'https'].indexOf(hrefUri.scheme) >= 0) {
+			return hrefUri.toString();
+		}
+
+		// Use href as file URI if it is absolute
+		if (path.isAbsolute(href) || hrefUri.scheme === 'file') {
+			return vscode.Uri.file(href)
+				.with({ scheme: 'vscode-resource' })
+				.toString();
+		}
+
+		// Use a workspace relative path if there is a workspace
+		let root = vscode.workspace.getWorkspaceFolder(resource);
+		if (root) {
+			return vscode.Uri.file(path.join(root.uri.fsPath, href))
+				.with({ scheme: 'vscode-resource' })
+				.toString();
+		}
+
+		// Otherwise look relative to the markdown file
+		return vscode.Uri.file(path.join(path.dirname(resource.fsPath), href))
+			.with({ scheme: 'vscode-resource' })
+			.toString();
+	}
+
+	private computeCustomStyleSheetIncludes(resource: vscode.Uri, config: MarkdownPreviewConfiguration): string {
+		if (Array.isArray(config.styles)) {
+			return config.styles.map(style => {
+				return `<link rel="stylesheet" class="code-user-style" data-source="${style.replace(/"/g, '&quot;')}" href="${this.fixHref(resource, style)}" type="text/css" media="screen">`;
+			}).join('\n');
+		}
+		return '';
+	}
+
+	private getSettingsOverrideStyles(nonce: string, config: MarkdownPreviewConfiguration): string {
+		return `<style nonce="${nonce}">
+			body {
+				${config.fontFamily ? `font-family: ${config.fontFamily};` : ''}
+				${isNaN(config.fontSize) ? '' : `font-size: ${config.fontSize}px;`}
+				${isNaN(config.lineHeight) ? '' : `line-height: ${config.lineHeight};`}
+			}
+		</style>`;
+	}
+
+	private getStyles(resource: vscode.Uri, nonce: string, config: MarkdownPreviewConfiguration): string {
+		const baseStyles = this.contributions.previewStyles
+			.map(resource => `<link rel="stylesheet" type="text/css" href="${resource.toString()}">`)
+			.join('\n');
+
+		return `${baseStyles}
+			${this.getSettingsOverrideStyles(nonce, config)}
+			${this.computeCustomStyleSheetIncludes(resource, config)}`;
+	}
+
+	private getScripts(nonce: string): string {
+		return this.contributions.previewScripts
+			.map(resource => `<script async src="${resource.toString()}" nonce="${nonce}" charset="UTF-8"></script>`)
+			.join('\n');
+	}
+
+	private getCspForResource(resource: vscode.Uri, nonce: string): string {
+		switch (this.cspArbiter.getSecurityLevelForResource(resource)) {
+			case MarkdownPreviewSecurityLevel.AllowInsecureContent:
+				return `<meta http-equiv="Content-Security-Policy" content="default-src 'none'; img-src vscode-resource: http: https: data:; media-src vscode-resource: http: https: data:; script-src 'nonce-${nonce}'; style-src vscode-resource: 'unsafe-inline' http: https: data:; font-src vscode-resource: http: https: data:;">`;
+
+			case MarkdownPreviewSecurityLevel.AllowScriptsAndAllContent:
+				return '';
+
+			case MarkdownPreviewSecurityLevel.Strict:
+			default:
+				return `<meta http-equiv="Content-Security-Policy" content="default-src 'none'; img-src vscode-resource: https: data:; media-src vscode-resource: https: data:; script-src 'nonce-${nonce}'; style-src vscode-resource: 'unsafe-inline' https: data:; font-src vscode-resource: https: data:;">`;
+		}
+	}
+}
--- a/extensions/markdown-language-features/src/features/previewManager.ts
+++ b/extensions/markdown-language-features/src/features/previewManager.ts
@@ -0,0 +1,144 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import * as vscode from 'vscode';
+
+import { Logger } from '../logger';
+import { MarkdownContentProvider } from './previewContentProvider';
+import { MarkdownPreview, PreviewSettings } from './preview';
+import { disposeAll } from '../util/dispose';
+import { MarkdownFileTopmostLineMonitor } from '../util/topmostLineMonitor';
+import { isMarkdownFile } from '../util/file';
+import { MarkdownPreviewConfigurationManager } from './previewConfig';
+import { MarkdownContributions } from '../markdownExtensions';
+
+export class MarkdownPreviewManager {
+	private static readonly markdownPreviewActiveContextKey = 'markdownPreviewFocus';
+
+	private readonly topmostLineMonitor = new MarkdownFileTopmostLineMonitor();
+	private readonly previewConfigurations = new MarkdownPreviewConfigurationManager();
+	private readonly previews: MarkdownPreview[] = [];
+	private activePreview: MarkdownPreview | undefined = undefined;
+	private readonly disposables: vscode.Disposable[] = [];
+
+	public constructor(
+		private readonly contentProvider: MarkdownContentProvider,
+		private readonly logger: Logger,
+		private readonly contributions: MarkdownContributions
+	) {
+		vscode.window.onDidChangeActiveEditor(editor => {
+			vscode.commands.executeCommand('setContext', MarkdownPreviewManager.markdownPreviewActiveContextKey,
+				editor && editor.editorType === 'webview' && editor.uri.scheme === MarkdownPreview.previewScheme);
+
+			this.activePreview = editor && editor.editorType === 'webview'
+				? this.previews.find(preview => editor.uri.toString() === preview.uri.toString())
+				: undefined;
+
+			if (editor && editor.editorType === 'texteditor') {
+				if (isMarkdownFile(editor.document)) {
+					for (const preview of this.previews.filter(preview => !preview.locked)) {
+						preview.update(editor.document.uri);
+					}
+				}
+			}
+		}, null, this.disposables);
+	}
+
+	public dispose(): void {
+		disposeAll(this.disposables);
+		disposeAll(this.previews);
+	}
+
+	public refresh() {
+		for (const preview of this.previews) {
+			preview.refresh();
+		}
+	}
+
+	public updateConfiguration() {
+		for (const preview of this.previews) {
+			preview.updateConfiguration();
+		}
+	}
+
+	public preview(
+		resource: vscode.Uri,
+		previewSettings: PreviewSettings
+	): void {
+		let preview = this.getExistingPreview(resource, previewSettings);
+		if (preview) {
+			preview.show(previewSettings.previewColumn);
+		} else {
+			preview = this.createNewPreview(resource, previewSettings);
+			this.previews.push(preview);
+		}
+
+		preview.update(resource);
+	}
+
+	public get activePreviewResource() {
+		return this.activePreview && this.activePreview.resource;
+	}
+
+	public getResourceForPreview(previewUri: vscode.Uri): vscode.Uri | undefined {
+		const preview = this.getPreviewWithUri(previewUri);
+		return preview && preview.resource;
+	}
+
+	public toggleLock(previewUri?: vscode.Uri) {
+		const preview = previewUri ? this.getPreviewWithUri(previewUri) : this.activePreview;
+		if (preview) {
+			preview.toggleLock();
+
+			// Close any previews that are now redundant, such as having two dynamic previews in the same editor group
+			for (const otherPreview of this.previews) {
+				if (otherPreview !== preview && preview.matches(otherPreview)) {
+					otherPreview.dispose();
+				}
+			}
+		}
+	}
+
+	private getExistingPreview(
+		resource: vscode.Uri,
+		previewSettings: PreviewSettings
+	): MarkdownPreview | undefined {
+		return this.previews.find(preview =>
+			preview.matchesResource(resource, previewSettings.previewColumn, previewSettings.locked));
+	}
+
+	private getPreviewWithUri(previewUri: vscode.Uri): MarkdownPreview | undefined {
+		return this.previews.find(preview => preview.uri.toString() === previewUri.toString());
+	}
+
+	private createNewPreview(
+		resource: vscode.Uri,
+		previewSettings: PreviewSettings
+	) {
+		const preview = new MarkdownPreview(
+			resource,
+			previewSettings.previewColumn,
+			previewSettings.locked,
+			this.contentProvider,
+			this.previewConfigurations,
+			this.logger,
+			this.topmostLineMonitor,
+			this.contributions);
+
+		preview.onDispose(() => {
+			const existing = this.previews.indexOf(preview!);
+			if (existing >= 0) {
+				this.previews.splice(existing, 1);
+			}
+		});
+
+		preview.onDidChangeViewColumn(() => {
+			disposeAll(this.previews.filter(otherPreview => preview !== otherPreview && preview!.matches(otherPreview)));
+		});
+
+		return preview;
+	}
+}
+
--- a/extensions/markdown-language-features/src/logger.ts
+++ b/extensions/markdown-language-features/src/logger.ts
@@ -0,0 +1,76 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import { OutputChannel, window, workspace } from 'vscode';
+
+enum Trace {
+	Off,
+	Verbose
+}
+
+namespace Trace {
+	export function fromString(value: string): Trace {
+		value = value.toLowerCase();
+		switch (value) {
+			case 'off':
+				return Trace.Off;
+			case 'verbose':
+				return Trace.Verbose;
+			default:
+				return Trace.Off;
+		}
+	}
+}
+
+
+function isString(value: any): value is string {
+	return Object.prototype.toString.call(value) === '[object String]';
+}
+
+export class Logger {
+	private trace?: Trace;
+	private _output?: OutputChannel;
+
+	constructor() {
+		this.updateConfiguration();
+	}
+
+	public log(message: string, data?: any): void {
+		if (this.trace === Trace.Verbose) {
+			this.output.appendLine(`[Log - ${(new Date().toLocaleTimeString())}] ${message}`);
+			if (data) {
+				this.output.appendLine(Logger.data2String(data));
+			}
+		}
+	}
+
+	public updateConfiguration() {
+		this.trace = this.readTrace();
+	}
+
+	private get output(): OutputChannel {
+		if (!this._output) {
+			this._output = window.createOutputChannel('Markdown');
+		}
+		return this._output;
+	}
+
+	private readTrace(): Trace {
+		return Trace.fromString(workspace.getConfiguration().get<string>('markdown.trace', 'off'));
+	}
+
+	private static data2String(data: any): string {
+		if (data instanceof Error) {
+			if (isString(data.stack)) {
+				return data.stack;
+			}
+			return (data as Error).message;
+		}
+		if (isString(data)) {
+			return data;
+		}
+		return JSON.stringify(data, undefined, 2);
+	}
+}
--- a/extensions/markdown-language-features/src/markdownEngine.ts
+++ b/extensions/markdown-language-features/src/markdownEngine.ts
@@ -0,0 +1,171 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import * as vscode from 'vscode';
+import * as path from 'path';
+import { Slug } from './tableOfContentsProvider';
+import { MarkdownIt, Token } from 'markdown-it';
+import { MarkdownContributions } from './markdownExtensions';
+
+const FrontMatterRegex = /^---\s*[^]*?(-{3}|\.{3})\s*/;
+
+export class MarkdownEngine {
+	private md?: MarkdownIt;
+
+	private firstLine?: number;
+
+	private currentDocument?: vscode.Uri;
+
+	public constructor(
+		private readonly extensionPreviewResourceProvider: MarkdownContributions
+	) { }
+
+	private usePlugin(factory: (md: any) => any): void {
+		try {
+			this.md = factory(this.md);
+		} catch (e) {
+			// noop
+		}
+	}
+
+	private async getEngine(resource: vscode.Uri): Promise<MarkdownIt> {
+		if (!this.md) {
+			const hljs = await import('highlight.js');
+			const mdnh = await import('markdown-it-named-headers');
+			this.md = (await import('markdown-it'))({
+				html: true,
+				highlight: (str: string, lang: string) => {
+					// Workaround for highlight not supporting tsx: https://github.com/isagalaev/highlight.js/issues/1155
+					if (lang && ['tsx', 'typescriptreact'].indexOf(lang.toLocaleLowerCase()) >= 0) {
+						lang = 'jsx';
+					}
+					if (lang && hljs.getLanguage(lang)) {
+						try {
+							return `<pre class="hljs"><code><div>${hljs.highlight(lang, str, true).value}</div></code></pre>`;
+						} catch (error) { }
+					}
+					return `<pre class="hljs"><code><div>${this.md!.utils.escapeHtml(str)}</div></code></pre>`;
+				}
+			}).use(mdnh, {
+				slugify: (header: string) => Slug.fromHeading(header).value
+			});
+
+			for (const plugin of this.extensionPreviewResourceProvider.markdownItPlugins) {
+				this.usePlugin(await plugin);
+			}
+
+			for (const renderName of ['paragraph_open', 'heading_open', 'image', 'code_block', 'blockquote_open', 'list_item_open']) {
+				this.addLineNumberRenderer(this.md, renderName);
+			}
+
+			this.addLinkNormalizer(this.md);
+			this.addLinkValidator(this.md);
+		}
+
+		const config = vscode.workspace.getConfiguration('markdown', resource);
+		this.md.set({
+			breaks: config.get<boolean>('preview.breaks', false),
+			linkify: config.get<boolean>('preview.linkify', true)
+		});
+		return this.md;
+	}
+
+	private stripFrontmatter(text: string): { text: string, offset: number } {
+		let offset = 0;
+		const frontMatterMatch = FrontMatterRegex.exec(text);
+		if (frontMatterMatch) {
+			const frontMatter = frontMatterMatch[0];
+			offset = frontMatter.split(/\r\n|\n|\r/g).length - 1;
+			text = text.substr(frontMatter.length);
+		}
+		return { text, offset };
+	}
+
+	public async render(document: vscode.Uri, stripFrontmatter: boolean, text: string): Promise<string> {
+		let offset = 0;
+		if (stripFrontmatter) {
+			const markdownContent = this.stripFrontmatter(text);
+			offset = markdownContent.offset;
+			text = markdownContent.text;
+		}
+		this.currentDocument = document;
+		this.firstLine = offset;
+		const engine = await this.getEngine(document);
+		return engine.render(text);
+	}
+
+	public async parse(document: vscode.Uri, source: string): Promise<Token[]> {
+		const { text, offset } = this.stripFrontmatter(source);
+		this.currentDocument = document;
+		const engine = await this.getEngine(document);
+
+		return engine.parse(text, {}).map(token => {
+			if (token.map) {
+				token.map[0] += offset;
+			}
+			return token;
+		});
+	}
+
+	private addLineNumberRenderer(md: any, ruleName: string): void {
+		const original = md.renderer.rules[ruleName];
+		md.renderer.rules[ruleName] = (tokens: any, idx: number, options: any, env: any, self: any) => {
+			const token = tokens[idx];
+			if (token.map && token.map.length) {
+				token.attrSet('data-line', this.firstLine + token.map[0]);
+				token.attrJoin('class', 'code-line');
+			}
+
+			if (original) {
+				return original(tokens, idx, options, env, self);
+			} else {
+				return self.renderToken(tokens, idx, options, env, self);
+			}
+		};
+	}
+
+	private addLinkNormalizer(md: any): void {
+		const normalizeLink = md.normalizeLink;
+		md.normalizeLink = (link: string) => {
+			try {
+				let uri = vscode.Uri.parse(link);
+				if (!uri.scheme && uri.path) {
+					// Assume it must be a file
+					const fragment = uri.fragment;
+					if (uri.path[0] === '/') {
+						const root = vscode.workspace.getWorkspaceFolder(this.currentDocument!);
+						if (root) {
+							uri = vscode.Uri.file(path.join(root.uri.fsPath, uri.path));
+						}
+					} else {
+						uri = vscode.Uri.file(path.join(path.dirname(this.currentDocument!.path), uri.path));
+					}
+
+					if (fragment) {
+						uri = uri.with({
+							fragment: Slug.fromHeading(fragment).value
+						});
+					}
+					return normalizeLink(uri.with({ scheme: 'vscode-resource' }).toString(true));
+				} else if (!uri.scheme && !uri.path && uri.fragment) {
+					return normalizeLink(uri.with({
+						fragment: Slug.fromHeading(uri.fragment).value
+					}).toString(true));
+				}
+			} catch (e) {
+				// noop
+			}
+			return normalizeLink(link);
+		};
+	}
+
+	private addLinkValidator(md: any): void {
+		const validateLink = md.validateLink;
+		md.validateLink = (link: string) => {
+			// support file:// links
+			return validateLink(link) || link.indexOf('file:') === 0;
+		};
+	}
+}
--- a/extensions/markdown-language-features/src/markdownExtensions.ts
+++ b/extensions/markdown-language-features/src/markdownExtensions.ts
@@ -0,0 +1,116 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import * as vscode from 'vscode';
+import * as path from 'path';
+
+const resolveExtensionResource = (extension: vscode.Extension<any>, resourcePath: string): vscode.Uri => {
+	return vscode.Uri.file(path.join(extension.extensionPath, resourcePath))
+		.with({ scheme: 'vscode-resource' });
+};
+
+const resolveExtensionResources = (extension: vscode.Extension<any>, resourcePaths: any): vscode.Uri[] => {
+	const result: vscode.Uri[] = [];
+	if (Array.isArray(resourcePaths)) {
+		for (const resource of resourcePaths) {
+			try {
+				result.push(resolveExtensionResource(extension, resource));
+			} catch (e) {
+				// noop
+			}
+		}
+	}
+	return result;
+};
+
+export interface MarkdownContributions {
+	readonly previewScripts: vscode.Uri[];
+	readonly previewStyles: vscode.Uri[];
+	readonly markdownItPlugins: Thenable<(md: any) => any>[];
+	readonly previewResourceRoots: vscode.Uri[];
+}
+
+class MarkdownExtensionContributions implements MarkdownContributions {
+	private readonly _scripts: vscode.Uri[] = [];
+	private readonly _styles: vscode.Uri[] = [];
+	private readonly _previewResourceRoots: vscode.Uri[] = [];
+	private readonly _plugins: Thenable<(md: any) => any>[] = [];
+
+	private _loaded = false;
+
+	public get previewScripts(): vscode.Uri[] {
+		this.ensureLoaded();
+		return this._scripts;
+	}
+
+	public get previewStyles(): vscode.Uri[] {
+		this.ensureLoaded();
+		return this._styles;
+	}
+
+	public get previewResourceRoots(): vscode.Uri[] {
+		this.ensureLoaded();
+		return this._previewResourceRoots;
+	}
+
+	public get markdownItPlugins(): Thenable<(md: any) => any>[] {
+		this.ensureLoaded();
+		return this._plugins;
+	}
+
+	private ensureLoaded() {
+		if (this._loaded) {
+			return;
+		}
+
+		this._loaded = true;
+		for (const extension of vscode.extensions.all) {
+			const contributes = extension.packageJSON && extension.packageJSON.contributes;
+			if (!contributes) {
+				continue;
+			}
+
+			this.tryLoadPreviewStyles(contributes, extension);
+			this.tryLoadPreviewScripts(contributes, extension);
+			this.tryLoadMarkdownItPlugins(contributes, extension);
+
+			if (contributes['markdown.previewScripts'] || contributes['markdown.previewStyles']) {
+				this._previewResourceRoots.push(vscode.Uri.file(extension.extensionPath));
+			}
+		}
+	}
+
+	private tryLoadMarkdownItPlugins(
+		contributes: any,
+		extension: vscode.Extension<any>
+	) {
+		if (contributes['markdown.markdownItPlugins']) {
+			this._plugins.push(extension.activate().then(() => {
+				if (extension.exports && extension.exports.extendMarkdownIt) {
+					return (md: any) => extension.exports.extendMarkdownIt(md);
+				}
+				return (md: any) => md;
+			}));
+		}
+	}
+
+	private tryLoadPreviewScripts(
+		contributes: any,
+		extension: vscode.Extension<any>
+	) {
+		this._scripts.push(...resolveExtensionResources(extension, contributes['markdown.previewScripts']));
+	}
+
+	private tryLoadPreviewStyles(
+		contributes: any,
+		extension: vscode.Extension<any>
+	) {
+		this._styles.push(...resolveExtensionResources(extension, contributes['markdown.previewStyles']));
+	}
+}
+
+export function getMarkdownExtensionContributions(): MarkdownContributions {
+	return new MarkdownExtensionContributions();
+}
--- a/extensions/markdown-language-features/src/security.ts
+++ b/extensions/markdown-language-features/src/security.ts
@@ -0,0 +1,154 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import * as vscode from 'vscode';
+
+import { MarkdownPreviewManager } from './features/previewManager';
+
+import * as nls from 'vscode-nls';
+
+const localize = nls.loadMessageBundle();
+
+export enum MarkdownPreviewSecurityLevel {
+	Strict = 0,
+	AllowInsecureContent = 1,
+	AllowScriptsAndAllContent = 2
+}
+
+export interface ContentSecurityPolicyArbiter {
+	getSecurityLevelForResource(resource: vscode.Uri): MarkdownPreviewSecurityLevel;
+
+	setSecurityLevelForResource(resource: vscode.Uri, level: MarkdownPreviewSecurityLevel): Thenable<void>;
+
+	shouldAllowSvgsForResource(resource: vscode.Uri): void;
+
+	shouldDisableSecurityWarnings(): boolean;
+
+	setShouldDisableSecurityWarning(shouldShow: boolean): Thenable<void>;
+}
+
+export class ExtensionContentSecurityPolicyArbiter implements ContentSecurityPolicyArbiter {
+	private readonly old_trusted_workspace_key = 'trusted_preview_workspace:';
+	private readonly security_level_key = 'preview_security_level:';
+	private readonly should_disable_security_warning_key = 'preview_should_show_security_warning:';
+
+	constructor(
+		private readonly globalState: vscode.Memento,
+		private readonly workspaceState: vscode.Memento
+	) { }
+
+	public getSecurityLevelForResource(resource: vscode.Uri): MarkdownPreviewSecurityLevel {
+		// Use new security level setting first
+		const level = this.globalState.get<MarkdownPreviewSecurityLevel | undefined>(this.security_level_key + this.getRoot(resource), undefined);
+		if (typeof level !== 'undefined') {
+			return level;
+		}
+
+		// Fallback to old trusted workspace setting
+		if (this.globalState.get<boolean>(this.old_trusted_workspace_key + this.getRoot(resource), false)) {
+			return MarkdownPreviewSecurityLevel.AllowScriptsAndAllContent;
+		}
+		return MarkdownPreviewSecurityLevel.Strict;
+	}
+
+	public setSecurityLevelForResource(resource: vscode.Uri, level: MarkdownPreviewSecurityLevel): Thenable<void> {
+		return this.globalState.update(this.security_level_key + this.getRoot(resource), level);
+	}
+
+	public shouldAllowSvgsForResource(resource: vscode.Uri) {
+		const securityLevel = this.getSecurityLevelForResource(resource);
+		return securityLevel === MarkdownPreviewSecurityLevel.AllowInsecureContent || securityLevel === MarkdownPreviewSecurityLevel.AllowScriptsAndAllContent;
+	}
+
+	public shouldDisableSecurityWarnings(): boolean {
+		return this.workspaceState.get<boolean>(this.should_disable_security_warning_key, false);
+	}
+
+	public setShouldDisableSecurityWarning(disabled: boolean): Thenable<void> {
+		return this.workspaceState.update(this.should_disable_security_warning_key, disabled);
+	}
+
+	private getRoot(resource: vscode.Uri): vscode.Uri {
+		if (vscode.workspace.workspaceFolders) {
+			const folderForResource = vscode.workspace.getWorkspaceFolder(resource);
+			if (folderForResource) {
+				return folderForResource.uri;
+			}
+
+			if (vscode.workspace.workspaceFolders.length) {
+				return vscode.workspace.workspaceFolders[0].uri;
+			}
+		}
+
+		return resource;
+	}
+}
+
+export class PreviewSecuritySelector {
+
+	public constructor(
+		private readonly cspArbiter: ContentSecurityPolicyArbiter,
+		private readonly webviewManager: MarkdownPreviewManager
+	) { }
+
+	public async showSecutitySelectorForResource(resource: vscode.Uri): Promise<void> {
+		interface PreviewSecurityPickItem extends vscode.QuickPickItem {
+			readonly type: 'moreinfo' | 'toggle' | MarkdownPreviewSecurityLevel;
+		}
+
+		function markActiveWhen(when: boolean): string {
+			return when ? '• ' : '';
+		}
+
+		const currentSecurityLevel = this.cspArbiter.getSecurityLevelForResource(resource);
+		const selection = await vscode.window.showQuickPick<PreviewSecurityPickItem>(
+			[
+				{
+					type: MarkdownPreviewSecurityLevel.Strict,
+					label: markActiveWhen(currentSecurityLevel === MarkdownPreviewSecurityLevel.Strict) + localize('strict.title', 'Strict'),
+					description: localize('strict.description', 'Only load secure content'),
+				}, {
+					type: MarkdownPreviewSecurityLevel.AllowInsecureContent,
+					label: markActiveWhen(currentSecurityLevel === MarkdownPreviewSecurityLevel.AllowInsecureContent) + localize('insecureContent.title', 'Allow insecure content'),
+					description: localize('insecureContent.description', 'Enable loading content over http'),
+				}, {
+					type: MarkdownPreviewSecurityLevel.AllowScriptsAndAllContent,
+					label: markActiveWhen(currentSecurityLevel === MarkdownPreviewSecurityLevel.AllowScriptsAndAllContent) + localize('disable.title', 'Disable'),
+					description: localize('disable.description', 'Allow all content and script execution. Not recommended'),
+				}, {
+					type: 'moreinfo',
+					label: localize('moreInfo.title', 'More Information'),
+					description: ''
+				}, {
+					type: 'toggle',
+					label: this.cspArbiter.shouldDisableSecurityWarnings()
+						? localize('enableSecurityWarning.title', "Enable preview security warnings in this workspace")
+						: localize('disableSecurityWarning.title', "Disable preview security warning in this workspace"),
+					description: localize('toggleSecurityWarning.description', 'Does not affect the content security level')
+				},
+			], {
+				placeHolder: localize(
+					'preview.showPreviewSecuritySelector.title',
+					'Select security settings for Markdown previews in this workspace'),
+			});
+
+		if (!selection) {
+			return;
+		}
+
+		if (selection.type === 'moreinfo') {
+			vscode.commands.executeCommand('vscode.open', vscode.Uri.parse('https://go.microsoft.com/fwlink/?linkid=854414'));
+			return;
+		}
+
+		if (selection.type === 'toggle') {
+			this.cspArbiter.setShouldDisableSecurityWarning(!this.cspArbiter.shouldDisableSecurityWarnings());
+			return;
+		} else {
+			await this.cspArbiter.setSecurityLevelForResource(resource, selection.type);
+		}
+		this.webviewManager.refresh();
+	}
+}
--- a/extensions/markdown-language-features/src/tableOfContentsProvider.ts
+++ b/extensions/markdown-language-features/src/tableOfContentsProvider.ts
@@ -0,0 +1,100 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import * as vscode from 'vscode';
+
+import { MarkdownEngine } from './markdownEngine';
+
+export class Slug {
+	private static specialChars: any = { 'à': 'a', 'ä': 'a', 'ã': 'a', 'á': 'a', 'â': 'a', 'æ': 'a', 'å': 'a', 'ë': 'e', 'è': 'e', 'é': 'e', 'ê': 'e', 'î': 'i', 'ï': 'i', 'ì': 'i', 'í': 'i', 'ò': 'o', 'ó': 'o', 'ö': 'o', 'ô': 'o', 'ø': 'o', 'ù': 'o', 'ú': 'u', 'ü': 'u', 'û': 'u', 'ñ': 'n', 'ç': 'c', 'ß': 's', 'ÿ': 'y', 'œ': 'o', 'ŕ': 'r', 'ś': 's', 'ń': 'n', 'ṕ': 'p', 'ẃ': 'w', 'ǵ': 'g', 'ǹ': 'n', 'ḿ': 'm', 'ǘ': 'u', 'ẍ': 'x', 'ź': 'z', 'ḧ': 'h', '·': '-', '/': '-', '_': '-', ',': '-', ':': '-', ';': '-' };
+
+	public static fromHeading(heading: string): Slug {
+		const slugifiedHeading = encodeURI(heading.trim()
+			.toLowerCase()
+			.replace(/./g, c => Slug.specialChars[c] || c)
+			.replace(/[\]\[\!\'\#\$\%\&\'\(\)\*\+\,\.\/\:\;\<\=\>\?\@\\\^\_\{\|\}\~\`]/g, '')
+			.replace(/\s+/g, '-') // Replace whitespace with -
+			.replace(/[^\w\-]+/g, '') // Remove remaining non-word chars
+			.replace(/^\-+/, '') // Remove leading -
+			.replace(/\-+$/, '') // Remove trailing -
+		);
+
+		return new Slug(slugifiedHeading);
+	}
+
+	private constructor(
+		public readonly value: string
+	) { }
+
+	public equals(other: Slug): boolean {
+		return this.value === other.value;
+	}
+}
+
+export interface TocEntry {
+	readonly slug: Slug;
+	readonly text: string;
+	readonly level: number;
+	readonly line: number;
+	readonly location: vscode.Location;
+}
+
+export class TableOfContentsProvider {
+	private toc?: TocEntry[];
+
+	public constructor(
+		private engine: MarkdownEngine,
+		private document: vscode.TextDocument
+	) { }
+
+	public async getToc(): Promise<TocEntry[]> {
+		if (!this.toc) {
+			try {
+				this.toc = await this.buildToc(this.document);
+			} catch (e) {
+				this.toc = [];
+			}
+		}
+		return this.toc;
+	}
+
+	public async lookup(fragment: string): Promise<TocEntry | undefined> {
+		const toc = await this.getToc();
+		const slug = Slug.fromHeading(fragment);
+		return toc.find(entry => entry.slug.equals(slug));
+	}
+
+	private async buildToc(document: vscode.TextDocument): Promise<TocEntry[]> {
+		const toc: TocEntry[] = [];
+		const tokens = await this.engine.parse(document.uri, document.getText());
+
+		for (const heading of tokens.filter(token => token.type === 'heading_open')) {
+			const lineNumber = heading.map[0];
+			const line = document.lineAt(lineNumber);
+			toc.push({
+				slug: Slug.fromHeading(line.text),
+				text: TableOfContentsProvider.getHeaderText(line.text),
+				level: TableOfContentsProvider.getHeaderLevel(heading.markup),
+				line: lineNumber,
+				location: new vscode.Location(document.uri, line.range)
+			});
+		}
+		return toc;
+	}
+
+	private static getHeaderLevel(markup: string): number {
+		if (markup === '=') {
+			return 1;
+		} else if (markup === '-') {
+			return 2;
+		} else { // '#', '##', ...
+			return markup.length;
+		}
+	}
+
+	private static getHeaderText(header: string): string {
+		return header.replace(/^\s*#+\s*(.*?)\s*#*$/, (_, word) => word.trim());
+	}
+}
--- a/extensions/markdown-language-features/src/telemetryReporter.ts
+++ b/extensions/markdown-language-features/src/telemetryReporter.ts
@@ -0,0 +1,60 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+import * as vscode from 'vscode';
+import { default as VSCodeTelemetryReporter } from 'vscode-extension-telemetry';
+
+interface IPackageInfo {
+	name: string;
+	version: string;
+	aiKey: string;
+}
+
+export interface TelemetryReporter {
+	dispose(): void;
+	sendTelemetryEvent(eventName: string, properties?: {
+		[key: string]: string;
+	}): void;
+}
+
+const nullReporter = new class NullTelemetryReporter implements TelemetryReporter {
+	sendTelemetryEvent() { /** noop */ }
+	dispose() { /** noop */ }
+};
+
+class ExtensionReporter implements TelemetryReporter {
+	private readonly _reporter: VSCodeTelemetryReporter;
+
+	constructor(
+		packageInfo: IPackageInfo
+	) {
+		this._reporter = new VSCodeTelemetryReporter(packageInfo.name, packageInfo.version, packageInfo.aiKey);
+	}
+	sendTelemetryEvent(eventName: string, properties?: {
+		[key: string]: string;
+	}) {
+		this._reporter.sendTelemetryEvent(eventName, properties);
+	}
+
+	dispose() {
+		this._reporter.dispose();
+	}
+}
+
+export function loadDefaultTelemetryReporter(): TelemetryReporter {
+	const packageInfo = getPackageInfo();
+	return packageInfo ? new ExtensionReporter(packageInfo) : nullReporter;
+}
+
+function getPackageInfo(): IPackageInfo | null {
+	const extention = vscode.extensions.getExtension('Microsoft.vscode-markdown');
+	if (extention && extention.packageJSON) {
+		return {
+			name: extention.packageJSON.name,
+			version: extention.packageJSON.version,
+			aiKey: extention.packageJSON.aiKey
+		};
+	}
+	return null;
+}
--- a/extensions/markdown-language-features/src/test/foldingProvider.test.ts
+++ b/extensions/markdown-language-features/src/test/foldingProvider.test.ts
@@ -0,0 +1,99 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import * as assert from 'assert';
+import * as vscode from 'vscode';
+import 'mocha';
+
+import { MarkdownEngine } from '../markdownEngine';
+import { MarkdownContributions } from '../markdownExtensions';
+import MarkdownFoldingProvider from '../features/foldingProvider';
+import { InMemoryDocument } from './inMemoryDocument';
+
+const testFileName = vscode.Uri.parse('test.md');
+
+suite('markdown.FoldingProvider', () => {
+	test('Should not return anything for empty document', async () => {
+		const folds = await getFoldsForDocument(``);
+		assert.strictEqual(folds.ranges.length, 0);
+	});
+
+	test('Should not return anything for document without headers', async () => {
+		const folds = await getFoldsForDocument(`a
+**b** afas
+a#b
+a`);
+		assert.strictEqual(folds.ranges.length, 0);
+	});
+
+	test('Should fold from header to end of document', async () => {
+		const folds = await getFoldsForDocument(`a
+# b
+c
+d`);
+		assert.strictEqual(folds.ranges.length, 1);
+		const firstFold = folds.ranges[0];
+		assert.strictEqual(firstFold.startLine, 1);
+		assert.strictEqual(firstFold.endLine, 3);
+	});
+
+	test('Should leave single newline before next header', async () => {
+		const folds = await getFoldsForDocument(`
+# a
+x
+
+# b
+y`);
+		assert.strictEqual(folds.ranges.length, 2);
+		const firstFold = folds.ranges[0];
+		assert.strictEqual(firstFold.startLine, 1);
+		assert.strictEqual(firstFold.endLine, 3);
+	});
+
+	test('Should collapse multuple newlines to single newline before next header', async () => {
+		const folds = await getFoldsForDocument(`
+# a
+x
+
+
+
+# b
+y`);
+		assert.strictEqual(folds.ranges.length, 2);
+		const firstFold = folds.ranges[0];
+		assert.strictEqual(firstFold.startLine, 1);
+		assert.strictEqual(firstFold.endLine, 5);
+	});
+
+	test('Should not collapse if there is no newline before next header', async () => {
+		const folds = await getFoldsForDocument(`
+# a
+x
+# b
+y`);
+		assert.strictEqual(folds.ranges.length, 2);
+		const firstFold = folds.ranges[0];
+		assert.strictEqual(firstFold.startLine, 1);
+		assert.strictEqual(firstFold.endLine, 2);
+	});
+
+});
+
+
+async function getFoldsForDocument(contents: string) {
+	const doc = new InMemoryDocument(testFileName, contents);
+	const provider = new MarkdownFoldingProvider(newEngine());
+	return await provider.provideFoldingRanges(doc, {}, new vscode.CancellationTokenSource().token);
+}
+
+function newEngine(): MarkdownEngine {
+	return new MarkdownEngine(new class implements MarkdownContributions {
+		readonly previewScripts: vscode.Uri[] = [];
+		readonly previewStyles: vscode.Uri[] = [];
+		readonly previewResourceRoots: vscode.Uri[] = [];
+		readonly markdownItPlugins: Promise<(md: any) => any>[]  = [];
+	});
+}
+
--- a/extensions/markdown-language-features/src/test/inMemoryDocument.ts
+++ b/extensions/markdown-language-features/src/test/inMemoryDocument.ts
@@ -0,0 +1,61 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import * as vscode from 'vscode';
+
+export class InMemoryDocument implements vscode.TextDocument {
+	private readonly _lines: string[];
+
+	constructor(
+		public readonly uri: vscode.Uri,
+		private readonly _contents: string
+	) {
+		this._lines = this._contents.split(/\n/g);
+	}
+
+	fileName: string = '';
+	isUntitled: boolean = false;
+	languageId: string = '';
+	version: number = 1;
+	isDirty: boolean = false;
+	isClosed: boolean = false;
+	eol: vscode.EndOfLine = vscode.EndOfLine.LF;
+
+	get lineCount(): number {
+		return this._lines.length;
+	}
+
+	lineAt(line: any): vscode.TextLine {
+		return {
+			lineNumber: line,
+			text: this._lines[line],
+			range: new vscode.Range(0, 0, 0, 0),
+			firstNonWhitespaceCharacterIndex: 0,
+			rangeIncludingLineBreak: new vscode.Range(0, 0, 0, 0),
+			isEmptyOrWhitespace: false
+		};
+	}
+	offsetAt(_position: vscode.Position): never {
+		throw new Error('Method not implemented.');
+	}
+	positionAt(_offset: number): never {
+		throw new Error('Method not implemented.');
+	}
+	getText(_range?: vscode.Range | undefined): string {
+		return this._contents;
+	}
+	getWordRangeAtPosition(_position: vscode.Position, _regex?: RegExp | undefined): never {
+		throw new Error('Method not implemented.');
+	}
+	validateRange(_range: vscode.Range): never {
+		throw new Error('Method not implemented.');
+	}
+	validatePosition(_position: vscode.Position): never {
+		throw new Error('Method not implemented.');
+	}
+	save(): never {
+		throw new Error('Method not implemented.');
+	}
+}
--- a/extensions/markdown-language-features/src/test/index.ts
+++ b/extensions/markdown-language-features/src/test/index.ts
@@ -0,0 +1,28 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+//
+// PLEASE DO NOT MODIFY / DELETE UNLESS YOU KNOW WHAT YOU ARE DOING
+//
+// This file is providing the test runner to use when running extension tests.
+// By default the test runner in use is Mocha based.
+//
+// You can provide your own test runner if you want to override it by exporting
+// a function run(testRoot: string, clb: (error:Error) => void) that the extension
+// host can call to run the tests. The test runner is expected to use console.log
+// to report the results back to the caller. When the tests are finished, return
+// a possible error to the callback or null if none.
+
+const testRunner = require('vscode/lib/testrunner');
+
+// You can directly control Mocha options by uncommenting the following lines
+// See https://github.com/mochajs/mocha/wiki/Using-mocha-programmatically#set-options for more info
+testRunner.configure({
+	ui: 'tdd', 		// the TDD UI is being used in extension.test.ts (suite, test, etc.)
+	useColors: process.platform !== 'win32', // colored output from test results (only windows cannot handle)
+	timeout: 60000
+});
+
+export = testRunner;
--- a/extensions/markdown-language-features/src/test/tableOfContentsProvider.test.ts
+++ b/extensions/markdown-language-features/src/test/tableOfContentsProvider.test.ts
@@ -0,0 +1,96 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import * as assert from 'assert';
+import * as vscode from 'vscode';
+import 'mocha';
+
+import { TableOfContentsProvider } from '../tableOfContentsProvider';
+import { MarkdownEngine } from '../markdownEngine';
+import { MarkdownContributions } from '../markdownExtensions';
+import { InMemoryDocument } from './inMemoryDocument';
+
+const testFileName = vscode.Uri.parse('test.md');
+
+suite('markdown.TableOfContentsProvider', () => {
+	test('Lookup should not return anything for empty document', async () => {
+		const doc = new InMemoryDocument(testFileName, '');
+		const provider = new TableOfContentsProvider(newEngine(), doc);
+
+		assert.strictEqual(await provider.lookup(''), undefined);
+		assert.strictEqual(await provider.lookup('foo'), undefined);
+	});
+
+	test('Lookup should not return anything for document with no headers', async () => {
+		const doc = new InMemoryDocument(testFileName, 'a *b*\nc');
+		const provider = new TableOfContentsProvider(newEngine(), doc);
+
+		assert.strictEqual(await provider.lookup(''), undefined);
+		assert.strictEqual(await provider.lookup('foo'), undefined);
+		assert.strictEqual(await provider.lookup('a'), undefined);
+		assert.strictEqual(await provider.lookup('b'), undefined);
+	});
+
+	test('Lookup should return basic #header', async () => {
+		const doc = new InMemoryDocument(testFileName, `# a\nx\n# c`);
+		const provider = new TableOfContentsProvider(newEngine(), doc);
+
+		{
+			const entry = await provider.lookup('a');
+			assert.ok(entry);
+			assert.strictEqual(entry!.line, 0);
+		}
+		{
+			assert.strictEqual(await provider.lookup('x'), undefined);
+		}
+		{
+			const entry = await provider.lookup('c');
+			assert.ok(entry);
+			assert.strictEqual(entry!.line, 2);
+		}
+	});
+
+	test('Lookups should be case in-sensitive', async () => {
+		const doc = new InMemoryDocument(testFileName, `# fOo\n`);
+		const provider = new TableOfContentsProvider(newEngine(), doc);
+
+		assert.strictEqual((await provider.lookup('fOo'))!.line, 0);
+		assert.strictEqual((await provider.lookup('foo'))!.line, 0);
+		assert.strictEqual((await provider.lookup('FOO'))!.line, 0);
+	});
+
+	test('Lookups should ignore leading and trailing white-space, and collapse internal whitespace', async () => {
+		const doc = new InMemoryDocument(testFileName, `#      f o  o    \n`);
+		const provider = new TableOfContentsProvider(newEngine(), doc);
+
+		assert.strictEqual((await provider.lookup('f o  o'))!.line, 0);
+		assert.strictEqual((await provider.lookup('  f o  o'))!.line, 0);
+		assert.strictEqual((await provider.lookup('  f o  o  '))!.line, 0);
+		assert.strictEqual((await provider.lookup('f o o'))!.line, 0);
+		assert.strictEqual((await provider.lookup('f o       o'))!.line, 0);
+
+		assert.strictEqual(await provider.lookup('f'), undefined);
+		assert.strictEqual(await provider.lookup('foo'), undefined);
+		assert.strictEqual(await provider.lookup('fo o'), undefined);
+	});
+
+	test('should normalize special characters #44779', async () => {
+		const doc = new InMemoryDocument(testFileName, `# Indentação\n`);
+		const provider = new TableOfContentsProvider(newEngine(), doc);
+
+		assert.strictEqual((await provider.lookup('indentacao'))!.line, 0);
+	});
+});
+
+function newEngine(): MarkdownEngine {
+	return new MarkdownEngine(new class implements MarkdownContributions {
+		readonly previewScripts: vscode.Uri[] = [];
+		readonly previewStyles: vscode.Uri[] = [];
+		readonly previewResourceRoots: vscode.Uri[] = [];
+		readonly markdownItPlugins: Promise<(md: any) => any>[]  = [];
+
+	});
+}
+
--- a/extensions/markdown-language-features/src/typings/markdown-it-named-headers.d.ts
+++ b/extensions/markdown-language-features/src/typings/markdown-it-named-headers.d.ts
@@ -0,0 +1,5 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+declare module 'markdown-it-named-headers' { }
--- a/extensions/markdown-language-features/src/typings/ref.d.ts
+++ b/extensions/markdown-language-features/src/typings/ref.d.ts
@@ -0,0 +1,8 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+/// <reference path='../../../../src/vs/vscode.d.ts'/>
+/// <reference path='../../../../src/vs/vscode.proposed.d.ts'/>
+/// <reference types='@types/node'/>
--- a/extensions/markdown-language-features/src/util/dispose.ts
+++ b/extensions/markdown-language-features/src/util/dispose.ts
@@ -0,0 +1,16 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import * as vscode from 'vscode';
+
+export function disposeAll(disposables: vscode.Disposable[]) {
+	while (disposables.length) {
+		const item = disposables.pop();
+		if (item) {
+			item.dispose();
+		}
+	}
+}
+
--- a/extensions/markdown-language-features/src/util/file.ts
+++ b/extensions/markdown-language-features/src/util/file.ts
@@ -0,0 +1,10 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import * as vscode from 'vscode';
+
+export function isMarkdownFile(document: vscode.TextDocument) {
+	return document.languageId === 'markdown';
+}
--- a/extensions/markdown-language-features/src/util/topmostLineMonitor.ts
+++ b/extensions/markdown-language-features/src/util/topmostLineMonitor.ts
@@ -0,0 +1,75 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import * as vscode from 'vscode';
+
+import { disposeAll } from '../util/dispose';
+import { isMarkdownFile } from './file';
+
+
+export class MarkdownFileTopmostLineMonitor {
+	private readonly disposables: vscode.Disposable[] = [];
+
+	private readonly pendingUpdates = new Map<string, number>();
+
+	constructor() {
+		vscode.window.onDidChangeTextEditorVisibleRanges(event => {
+			if (isMarkdownFile(event.textEditor.document)) {
+				const line = getVisibleLine(event.textEditor);
+				if (line) {
+					this.updateLine(event.textEditor.document.uri, line);
+				}
+			}
+		}, null, this.disposables);
+	}
+
+	dispose() {
+		disposeAll(this.disposables);
+	}
+
+	private readonly _onDidChangeTopmostLineEmitter = new vscode.EventEmitter<{ resource: vscode.Uri, line: number }>();
+	public readonly onDidChangeTopmostLine = this._onDidChangeTopmostLineEmitter.event;
+
+	private updateLine(
+		resource: vscode.Uri,
+		line: number
+	) {
+		const key = resource.toString();
+		if (!this.pendingUpdates.has(key)) {
+			// schedule update
+			setTimeout(() => {
+				if (this.pendingUpdates.has(key)) {
+					this._onDidChangeTopmostLineEmitter.fire({
+						resource,
+						line: this.pendingUpdates.get(key) as number
+					});
+					this.pendingUpdates.delete(key);
+				}
+			}, 50);
+		}
+
+		this.pendingUpdates.set(key, line);
+	}
+}
+
+/**
+ * Get the top-most visible range of `editor`.
+ *
+ * Returns a fractional line number based the visible character within the line.
+ * Floor to get real line number
+ */
+export function getVisibleLine(
+	editor: vscode.TextEditor
+): number | undefined {
+	if (!editor.visibleRanges.length) {
+		return undefined;
+	}
+
+	const firstVisiblePosition = editor.visibleRanges[0].start;
+	const lineNumber = firstVisiblePosition.line;
+	const line = editor.document.lineAt(lineNumber);
+	const progress = firstVisiblePosition.character / (line.text.length + 2);
+	return lineNumber + progress;
+}
--- a/extensions/markdown-language-features/tsconfig.json
+++ b/extensions/markdown-language-features/tsconfig.json
@@ -0,0 +1,22 @@
+{
+	"compilerOptions": {
+		"module": "commonjs",
+		"target": "es2017",
+		"lib": [
+			"es6",
+			"es2015.promise",
+			"dom"
+		],
+		"outDir": "./out",
+		"sourceMap": true,
+		"noImplicitAny": true,
+		"noImplicitReturns": true,
+		"noUnusedLocals": true,
+		"noUnusedParameters": true,
+		"strict": true,
+		"alwaysStrict": true
+	},
+	"include": [
+		"src/**/*"
+	]
+}
--- a/extensions/markdown-language-features/webpack.config.js
+++ b/extensions/markdown-language-features/webpack.config.js
@@ -0,0 +1,29 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+const path = require('path');
+
+module.exports = {
+	entry: {
+		index: './preview-src/index.ts',
+		pre: './preview-src/pre.ts'
+	},
+	module: {
+		rules: [
+			{
+				test: /\.tsx?$/,
+				use: 'ts-loader',
+				exclude: /node_modules/
+			}
+		]
+	},
+	resolve: {
+		extensions: ['.tsx', '.ts', '.js']
+	},
+	devtool: 'inline-source-map',
+	output: {
+		filename: '[name].js',
+		path: path.resolve(__dirname, 'media')
+	}
+};
--- a/extensions/markdown-language-features/yarn.lock
+++ b/extensions/markdown-language-features/yarn.lock
				`@@ -0,0 +1 @@`
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