Recovers markdown preview content on tab visibility changes

Addresses issues where markdown previews may display corrupted or
outdated content
by detecting tab visibility changes and forcing content recovery for
affected documents.
Improves reliability of previews when switching tabs or reopening custom
editors.
(#4328, #4489)

Author: sergeibbb

src/documents/markdown.ts

@@ -1,5 +1,5 @@
-import type { Disposable, Event, TextDocumentContentProvider } from 'vscode';
-import { EventEmitter, Uri, workspace } from 'vscode';
+import type { Event, TabChangeEvent, TextDocumentContentProvider } from 'vscode';
+import { Disposable, EventEmitter, TabInputCustom, Uri, window, workspace } from 'vscode';
 import { Schemes } from '../constants';
 import type { GlCommands } from '../constants.commands';
 import type { Container } from '../container';
@@ -17,6 +17,7 @@ export interface MarkdownContentMetadata {
 export class MarkdownContentProvider implements TextDocumentContentProvider {
 	private contents = new Map<string, string>();
 	private registration: Disposable;
+	private visibilityTracker: Disposable;
 
 	private _onDidChange = new EventEmitter<Uri>();
 	get onDidChange(): Event<Uri> {
@@ -26,6 +27,18 @@ export class MarkdownContentProvider implements TextDocumentContentProvider {
 	constructor(private container: Container) {
 		this.registration = workspace.registerTextDocumentContentProvider(Schemes.GitLensAIMarkdown, this);
 
+		// Track document visibility to detect when content needs recovery
+		this.visibilityTracker = Disposable.from(
+			window.tabGroups.onDidChangeTabs((e: TabChangeEvent) => {
+				this.onTabsChanged(e);
+			}),
+			// // Also track when tabs change which might affect preview visibility
+			// window.onDidChangeActiveTextEditor(() => {
+			// 	// Delay to allow VS Code to finish tab switching
+			// 	setTimeout(() => this.forceRecoveryForAllOpenedDocuments(), 1000);
+			// }),
+		);
+
 		workspace.onDidCloseTextDocument(document => {
 			if (document.uri.scheme === Schemes.GitLensAIMarkdown) {
 				this.contents.delete(document.uri.toString());
@@ -71,13 +84,66 @@ export class MarkdownContentProvider implements TextDocumentContentProvider {
 		this._onDidChange.fire(uri);
 	}
 
+	/**
+	 * Forces content recovery for a document - useful when content gets corrupted
+	 */
+	forceContentRecovery(uri: Uri): void {
+		const uriString = uri.toString();
+		if (!this.contents.has(uriString)) return;
+
+		const storedContent = this.contents.get(uriString);
+		if (!storedContent) return;
+
+		// I'm deleting the content because if I just fire the change once to make VSCode
+		// reach our `provideTextDocumentContent` method
+		// and `provideTextDocumentContent` returns the unchanged conent,
+		// VSCode will not refresh the content, instead it keeps displaying the original conetnt
+		// that the view had when it was opened initially.
+		// That's why I need to blink the content.
+		if (storedContent.at(storedContent.length - 1) === '\n') {
+			this.contents.set(uriString, storedContent.substring(0, storedContent.length - 1));
+		} else {
+			this.contents.set(uriString, `${storedContent}\n`);
+		}
+		this._onDidChange.fire(uri);
+	}
+
 	closeDocument(uri: Uri): void {
 		this.contents.delete(uri.toString());
 	}
 
 	dispose(): void {
 		this.contents.clear();
 		this.registration.dispose();
+		this.visibilityTracker.dispose();
+	}
+
+	// /**
+	//  * Checks preview visibility by examining workspace documents
+	//  */
+	// private forceRecoveryForAllOpenedDocuments(): void {
+	// 	// Check all workspace documents for our markdown scheme
+	// 	for (const document of workspace.textDocuments) {
+	// 		if (document.uri.scheme === Schemes.GitLensAIMarkdown) {
+	// 			const uriString = document.uri.toString();
+	// 			if (this.contents.has(uriString)) {
+	// 				console.log(`[GitLens] Checking preview visibility for: ${document.uri.path}`);
+	// 				// Trigger recovery check for this document
+	// 				setTimeout(() => {
+	// 					this.forceContentRecovery(document.uri);
+	// 				}, 1000);
+	// 			}
+	// 		}
+	// 	}
+	// }
+
+	private onTabsChanged(e: TabChangeEvent) {
+		for (const tab of e.changed) {
+			if (tab.input instanceof TabInputCustom && tab.input.uri.scheme === Schemes.GitLensAIMarkdown) {
+				const uri = tab.input.uri;
+				this.forceContentRecovery(uri);
+			}
+		}
 	}
 }