allow images in markdown preview editor to be copied (microsoft#184432)

* allow images in markdown preview editor to be copied

* resolved feedback

* added findPreview method

* removed copy image command from showPreview

* clean up

---------

Co-authored-by: Meghan Kulkarni <[email protected]>

Author: MeghanKulkarni

extensions/markdown-language-features/package.json

@@ -121,6 +121,10 @@
       }
     ],
     "commands": [
+      {
+        "command": "_markdown.copyImage",
+        "title": "%markdown.copyImage.title%"
+      },
       {
         "command": "markdown.showPreview",
         "title": "%markdown.preview.title%",
@@ -182,6 +186,12 @@
       }
     ],
     "menus": {
+      "webview/context": [
+        {
+          "command": "_markdown.copyImage",
+          "when": "webviewId == 'markdown.preview' && webviewSection == 'image'"
+        }
+      ],
       "editor/title": [
         {
           "command": "markdown.showPreviewToSide",

extensions/markdown-language-features/package.nls.json

@@ -1,6 +1,7 @@
 {
 	"displayName": "Markdown Language Features",
 	"description": "Provides rich language support for Markdown.",
+	"markdown.copyImage.title": "Copy Image",
 	"markdown.preview.breaks.desc": "Sets how line-breaks are rendered in the Markdown preview. Setting it to 'true' creates a <br> for newlines inside paragraphs.",
 	"markdown.preview.linkify": "Convert URL-like text to links in the Markdown preview.",
 	"markdown.preview.typographer": "Enable some language-neutral replacement and quotes beautification in the Markdown preview.",

extensions/markdown-language-features/preview-src/index.ts

@@ -63,6 +63,7 @@ function doAfterImagesLoaded(cb: () => void) {
 onceDocumentLoaded(() => {
 	const scrollProgress = state.scrollProgress;
 
+	addImageContexts();
 	if (typeof scrollProgress === 'number' && !settings.settings.fragment) {
 		doAfterImagesLoaded(() => {
 			scrollDisabledCount += 1;
@@ -125,9 +126,58 @@ window.addEventListener('resize', () => {
 	updateScrollProgress();
 }, true);
 
+function addImageContexts() {
+	const images = document.getElementsByTagName('img');
+	let idNumber = 0;
+	for (const img of images) {
+		img.id = 'image-' + idNumber;
+		idNumber += 1;
+		img.setAttribute('data-vscode-context', JSON.stringify({ webviewSection: 'image', id: img.id, 'preventDefaultContextMenuItems': true, resource: documentResource }));
+	}
+}
+
+async function copyImage(image: HTMLImageElement, retries = 5) {
+	if (!document.hasFocus() && retries > 0) {
+		// copyImage is called at the same time as webview.reveal, which means this function is running whilst the webview is gaining focus.
+		// Since navigator.clipboard.write requires the document to be focused, we need to wait for focus.
+		// We cannot use a listener, as there is a high chance the focus is gained during the setup of the listener resulting in us missing it.
+		setTimeout(() => { copyImage(image, retries - 1); }, 20);
+		return;
+	}
+
+	try {
+		await navigator.clipboard.write([new ClipboardItem({
+			'image/png': new Promise((resolve) => {
+				const canvas = document.createElement('canvas');
+				if (canvas !== null) {
+					canvas.width = image.naturalWidth;
+					canvas.height = image.naturalHeight;
+					const context = canvas.getContext('2d');
+					context?.drawImage(image, 0, 0);
+				}
+				canvas.toBlob((blob) => {
+					if (blob) {
+						resolve(blob);
+					}
+					canvas.remove();
+				}, 'image/png');
+			})
+		})]);
+	} catch (e) {
+		console.error(e);
+	}
+}
+
 window.addEventListener('message', async event => {
 	const data = event.data as ToWebviewMessage.Type;
 	switch (data.type) {
+		case 'copyImage': {
+			const img = document.getElementById(data.id);
+			if (img instanceof HTMLImageElement) {
+				copyImage(img);
+			}
+			return;
+		}
 		case 'onDidChangeTextEditorSelection':
 			if (data.source === documentResource) {
 				marker.onDidChangeTextEditorSelection(data.line, documentVersion);
@@ -239,6 +289,7 @@ window.addEventListener('message', async event => {
 			++documentVersion;
 
 			window.dispatchEvent(new CustomEvent('vscode.markdown.updateContent'));
+			addImageContexts();
 			break;
 		}
 	}

extensions/markdown-language-features/src/commands/copyImage.ts

@@ -0,0 +1,21 @@
+/*---------------------------------------------------------------------------------------------
+ *  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 '../preview/previewManager';
+
+export class CopyImageCommand implements Command {
+	public readonly id = '_markdown.copyImage';
+
+	public constructor(
+		private readonly _webviewManager: MarkdownPreviewManager,
+	) { }
+
+	public execute(args: { id: string; resource: string }) {
+		const source = vscode.Uri.parse(args.resource);
+		this._webviewManager.findPreview(source)?.copyImage(args.id);
+	}
+}

extensions/markdown-language-features/src/commands/index.ts

@@ -14,6 +14,7 @@ import { RefreshPreviewCommand } from './refreshPreview';
 import { ReloadPlugins } from './reloadPlugins';
 import { RenderDocument } from './renderDocument';
 import { ShowLockedPreviewToSideCommand, ShowPreviewCommand, ShowPreviewToSideCommand } from './showPreview';
+import { CopyImageCommand } from './copyImage';
 import { ShowPreviewSecuritySelectorCommand } from './showPreviewSecuritySelector';
 import { ShowSourceCommand } from './showSource';
 import { ToggleLockCommand } from './toggleLock';
@@ -27,6 +28,7 @@ export function registerMarkdownCommands(
 ): vscode.Disposable {
 	const previewSecuritySelector = new PreviewSecuritySelector(cspArbiter, previewManager);
 
+	commandManager.register(new CopyImageCommand(previewManager));
 	commandManager.register(new ShowPreviewCommand(previewManager, telemetryReporter));
 	commandManager.register(new ShowPreviewToSideCommand(previewManager, telemetryReporter));
 	commandManager.register(new ShowLockedPreviewToSideCommand(previewManager, telemetryReporter));

extensions/markdown-language-features/src/preview/preview.ts

@@ -442,8 +442,8 @@ export interface IManagedMarkdownPreview {
 	readonly onDispose: vscode.Event<void>;
 	readonly onDidChangeViewState: vscode.Event<vscode.WebviewPanelOnDidChangeViewStateEvent>;
 
+	copyImage(id: string): void;
 	dispose(): void;
-
 	refresh(): void;
 	updateConfiguration(): void;
 
@@ -515,6 +515,15 @@ export class StaticMarkdownPreview extends Disposable implements IManagedMarkdow
 		}));
 	}
 
+	copyImage(id: string) {
+		this._webviewPanel.reveal();
+		this._preview.postMessage({
+			type: 'copyImage',
+			source: this.resource.toString(),
+			id: id
+		});
+	}
+
 	private readonly _onDispose = this._register(new vscode.EventEmitter<void>());
 	public readonly onDispose = this._onDispose.event;
 
@@ -661,6 +670,15 @@ export class DynamicMarkdownPreview extends Disposable implements IManagedMarkdo
 		}));
 	}
 
+	copyImage(id: string) {
+		this._webviewPanel.reveal();
+		this._preview.postMessage({
+			type: 'copyImage',
+			source: this.resource.toString(),
+			id: id
+		});
+	}
+
 	private readonly _onDisposeEmitter = this._register(new vscode.EventEmitter<void>());
 	public readonly onDispose = this._onDisposeEmitter.event;
 

extensions/markdown-language-features/src/preview/previewManager.ts

@@ -147,6 +147,15 @@ export class MarkdownPreviewManager extends Disposable implements vscode.Webview
 		return this._activePreview?.resourceColumn;
 	}
 
+	public findPreview(resource: vscode.Uri): IManagedMarkdownPreview | undefined {
+		for (const preview of [...this._dynamicPreviews, ...this._staticPreviews]) {
+			if (preview.resource.fsPath === resource.fsPath) {
+				return preview;
+			}
+		}
+		return undefined;
+	}
+
 	public toggleLock() {
 		const preview = this._activePreview;
 		if (preview instanceof DynamicMarkdownPreview) {

extensions/markdown-language-features/types/previewMessaging.d.ts

@@ -65,9 +65,16 @@ export namespace ToWebviewMessage {
 		readonly content: string;
 	}
 
+	export interface CopyImageContent extends BaseMessage {
+		readonly type: 'copyImage';
+		readonly source: string;
+		readonly id: string;
+	}
+
 	export type Type =
 		| OnDidChangeTextEditorSelection
 		| UpdateView
 		| UpdateContent
+		| CopyImageContent
 		;
 }