Rename markdown to markdown-language-features

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;
+}