Polishing mermaid rendering

[mjbvz]

Fixes #271371

• Hook up more webview details
• Basic pan zoom
• Context menu support for output renderers

[Copilot]

Pull request overview

Polishes Mermaid chat output rendering by improving webview integration (state/context) and adding pan/zoom + a reset action via the webview context menu.

Changes:

• Persist and restore chat-output webview state (webview.state) across re-renders.
• Provide webview context metadata (providedViewType, scoped context keys) so webview/context menu contributions work.
• Add Mermaid webview pan/zoom support and a “Reset Pan and Zoom” command exposed in the webview context menu.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
src/vs/workbench/contrib/chat/browser/widget/chatContentParts/toolInvocationParts/chatToolOutputPart.ts	Passes persisted webviewState into renderer and stores state updates from the webview.
src/vs/workbench/contrib/chat/browser/chatOutputItemRenderer.ts	Sets providedViewType, scopes context keys to the webview container, and restores webview.state before mount.
src/vs/workbench/api/browser/mainThreadChatOutputRenderer.ts	Returns the ext-host render promise from the renderer callback (but currently misses unregister lifecycle wiring).
extensions/mermaid-chat-features/src/extension.ts	Adds reset command and webview context metadata; tracks a webview for reset messaging.
extensions/mermaid-chat-features/package.json	Contributes the reset command and webview context menu entry.
extensions/mermaid-chat-features/chat-webview-src/index.ts	Implements pan/zoom + persisted state in the Mermaid webview and listens for reset messages.

Comments suppressed due to low confidence (1)

src/vs/workbench/api/browser/mainThreadChatOutputRenderer.ts:52

• The disposable returned by _rendererService.registerRenderer(...) is currently ignored, so registeredRenderers is never populated and $unregisterChatOutputRenderer/dispose() cannot actually unregister renderers. Store the returned disposable in registeredRenderers (and delete it on unregister) so renderer registration lifecycle matches the ext host’s disposable.

				return this._proxy.$renderChatOutput(viewType, mime, VSBuffer.wrap(data), webviewHandle, token);
			},
		}, {
			extension: { id: extensionId, location: URI.revive(extensionLocation) }
		});

[Copilot]

This if block is a no-op (partState.webviewOrigin is assigned to itself) and can be removed. If the intent was to persist a generated/actual origin across re-renders, store the real origin value instead (and consider keeping webviewOrigin readonly unless it is intentionally mutated).

Suggested change

	if (partState.webviewOrigin) {
	partState.webviewOrigin = partState.webviewOrigin;
	}

[Copilot]

Tracking a single global activeWebview can reset the wrong diagram when multiple Mermaid outputs are present (the context menu command is invoked for the clicked webview, not necessarily the last rendered one). Consider passing a per-webview instance id via data-vscode-context and using the command argument to look up the correct webview to message (or another mechanism that targets the invoking webview).

[Copilot]

This command title is user-facing but is not localized. Consider switching to a %...% placeholder and adding the string to package.nls.json (as is already done for displayName, description, and config descriptions).

Suggested change

	"title": "Reset Pan and Zoom"
	"title": "%mermaidChat.resetPanZoom.title%"

[Copilot]

init is async but its returned promise is ignored. If mermaid.run(...) rejects, this becomes an unhandled promise rejection in the webview. Consider prefixing with void and/or adding a .catch(...) handler.

Suggested change

	init();
	void init().catch(error => {
	console.error('Failed to initialize mermaid webview', error);
	});

[Copilot]

The VsCodeApi interface uses any for state and messages, which loses type safety and can hide errors in this new pan/zoom + messaging code. Consider using unknown/generics (e.g. getState(): PanZoomState | undefined, typed message union) or at least constraining to Record<string, unknown> where appropriate.

Suggested change

	interface VsCodeApi {
	getState(): any;
	setState(state: any): void;
	postMessage(message: any): void;
	}
	declare function acquireVsCodeApi(): VsCodeApi;
	interface PanZoomState {
	scale: number;
	translateX: number;
	translateY: number;
	}
	class PanZoomHandler {
	private scale = 1;
	private translateX = 0;
	interface PanZoomState {
	scale: number;
	translateX: number;
	translateY: number;
	}
	interface VsCodeApi {
	getState(): PanZoomState | undefined;
	setState(state: PanZoomState): void;
	postMessage(message: Record<string, unknown>): void;
	}
	declare function acquireVsCodeApi(): VsCodeApi;
	class PanZoomHandler {
	private scale = 1;
	private translateX = 0;
	private translateX = 0;