vscode-extension-samples/previewhtml-sample/README.md

# CSS Properties Preview Sample
This is an sample extension that illustrates the use of virtual documents or `TextDocumentContentProviders` together with the `vscode.previewHtml`
[command](https://code.visualstudio.com/docs/extensionAPI/vscode-api-commands#_commands).

It is not intended as a product quality extension.

The purpose of the extension is to show a preview of the properties in the declaration block of a CSS rule. To play with the extension:
- Open a CSS file
- Use `Show CSS Properties Preview`
- Position the cursor inside the declaration block of the rule
- The properties are rendered in the preview
- Edit the properties and the preview is updated

![Navigation](images/preview.gif)

# How it works

- The extension implements and registers a [`TextDocumentContentProvider`](http://code.visualstudio.com/docs/extensionAPI/vscode-api#TextDocumentContentProvider) for a particular URI scheme.
- The content provider creates a HTML document that contains the declaration block of the selected CSS rule in the active editor.
- The generated HTML document contains a link that invokes a contributed command to highlight the CSS rule in the source editor
- The generated HTML document is then opened in an editor in the 2nd Column using the command `vscode.previewHtml`.

# How to run locally

* `npm install`
* `npm run compile` to start the compiler in watch mode
* open this folder in VS Code and press `F5`