Fixes#8488
**Bug**
Currently there is no indication in the markdown preview when a `markdown.styles` element fails to load
**Fix**
Show an alert then a stylesheet does not load
Fixes#21511Fixes#23922
Changes the default markdown toolbar item to open the preview to the side of the current file as requested by #21511
Also updates the single file preview icon slightly to better differentiate it from the diff icon
Two changes:
* Changes the logic from 41467b74b7 to make the padding customizable. The default 20px padding is preserved, but now preview can customize if they want to use it or not. This allows html preview page background colors to correctly fill the entire frame.
* Remove Writing the `_defaultStyles` to the root of the webview elment. These are only needed inside of the iFrame itself
Adds enhanced security settings for the markdown preview. The new flow disable all scripts within the preview itself. Users can enable scripts on a per workspace basis.
When a markdown document that uses scripts is loaded, a warning is shown inside the document itself. This warning triggers a new security selector quick pick which allows users to enable or disable enahanced security in the workspace.
Fixes#7776
**Bug**
Code blocks in the markdown preview are not very good looking
**Fix**
Use default text color for indented code blocks and add a background
**Bug**
When refreshing a webview, a slight flicker can sometime be seen. This is especially noticable when using the markdown preview.
**Fix**
Instead of replacing the content of the iframe for refresh, create a new iframe with the new content and do a swap to update.
Adds an initial implementation of scroll synrconization from the markdown preview to the editor. When the preview is scrolled, automatically scrolls the editor to reveal the same location.
This required adding a new supported reveal type `AtTop` in our API. This is already supported and used internally, but not really exposed in the public apis (except for the `revealLine` command).
* Adds command to post a message to an html preview
**Bug**
There is currently no easy way to communicate with an html preview document after the preview has been created.
**Fix**
Adds a command called `vscode.htmlPreview.postMessage` to post a message to a visible html preview. This message will only be posted if the target preview is visible.
Inside the preview, the event is recieved using the standard dom event:
* Remove logging
* proto
Continue proto
* clean up rendering
* Gate prototype
* Fix gating
* Remove public command
* Change setting name
* Added current position indicator
* Reveal center
* Improve markdown Wrapping
Includes a few improvements to the markdown preview
* Use breakword by default to break up very long words
* When `editor.worWrap` is enabled, wrap code blocks inside of the html preview.
* Reverts 41467b74b7 . This change is adding an 20px margin to the left of any html content. I believe the html content itself should be responsible for adding this padding and should normally fill the entire screen.
* Better centers markdown preview content
* Move padding to default webview style
* Remove padding change for now
* Allow markdown preview to scroll past content
Issue #15795
Allows the markdown preview to scroll past its contents, like we do with the editor.
Closes#15795
* Toggle preview scroll beyond using editor.scrollBeyondLastLine
**Bug**
In Markdown preview, code blocks in headers are the wrong font size.
**Fix**
Specify that code blocks in headers should inherit their font-size, instead of brining their own.
