fix: guard whiteboard permission rejections

src/components/TldrawWhiteboard.test.tsx

@@ -125,6 +125,13 @@ function mockEditor(): Editor {
   } as unknown as Editor
 }
 
+function dispatchUnhandledRejection(reason: unknown): Event {
+  const event = new Event('unhandledrejection', { cancelable: true })
+  Object.defineProperty(event, 'reason', { value: reason })
+  window.dispatchEvent(event)
+  return event
+}
+
 function measuredTextElement(): HTMLElement {
   const element = document.createElement('div')
   element.textContent = 'Label'
@@ -246,6 +253,31 @@ describe('TldrawWhiteboard', () => {
     expect(() => editor.textMeasure.measureElementTextNodeSpans(measuredTextElement())).toThrow('top')
   })
 
+  it('suppresses whiteboard platform permission rejections while mounted', () => {
+    render(
+      <TldrawWhiteboard
+        boardId="board-1"
+        height="520"
+        snapshot=""
+        width=""
+        onSizeChange={vi.fn()}
+        onSnapshotChange={vi.fn()}
+      />
+    )
+
+    const cleanup = renderedTldrawProps().onMount(mockEditor())
+    const denied = {
+      name: 'NotAllowedError',
+      message: 'The request is not allowed by the user agent or the platform in the current context, possibly because the user denied permission.',
+    }
+
+    expect(dispatchUnhandledRejection(denied).defaultPrevented).toBe(true)
+    expect(dispatchUnhandledRejection(new Error('save failed')).defaultPrevented).toBe(false)
+
+    cleanup()
+    expect(dispatchUnhandledRejection(denied).defaultPrevented).toBe(false)
+  })
+
   it('resets the drawing store when switching to a blank board snapshot', () => {
     const boardASnapshot = { records: { shape: 'from-board-a' } }
     const { rerender } = render(

src/components/TldrawWhiteboard.tsx

@@ -101,6 +101,50 @@ function ignoreTldrawUserPreferencesUpdate(preferences: TLUserPreferences) {
   void preferences
 }
 
+function rejectionName(error: unknown): string {
+  if (error instanceof Error) return error.name
+  if (typeof error !== 'object' || error === null || !('name' in error)) return ''
+
+  const { name } = error
+  return typeof name === 'string' ? name : ''
+}
+
+function rejectionMessage(error: unknown): string {
+  if (error instanceof Error) return error.message
+  if (typeof error === 'string') return error
+  if (typeof error !== 'object' || error === null || !('message' in error)) return ''
+
+  const { message } = error
+  return typeof message === 'string' ? message : ''
+}
+
+function isWhiteboardPlatformPermissionRejection(reason: unknown): boolean {
+  const name = rejectionName(reason).toLowerCase()
+  const message = rejectionMessage(reason).toLowerCase()
+  if (name === 'notallowederror') return true
+
+  return message.includes('notallowederror') || (
+    message.includes('not allowed')
+    && (
+      message.includes('permission')
+      || message.includes('platform')
+      || message.includes('user agent')
+    )
+  )
+}
+
+function installTldrawPlatformPermissionGuard(): () => void {
+  const handleUnhandledRejection = (event: PromiseRejectionEvent) => {
+    if (!isWhiteboardPlatformPermissionRejection(event.reason)) return
+    event.preventDefault()
+  }
+
+  window.addEventListener('unhandledrejection', handleUnhandledRejection)
+  return () => {
+    window.removeEventListener('unhandledrejection', handleUnhandledRejection)
+  }
+}
+
 function parseSnapshot(source: string): TLStoreSnapshot | null {
   if (!source.trim()) return null
 
@@ -211,8 +255,10 @@ function installZoomAwareViewport(editor: Editor): () => void {
 function installWhiteboardRuntimeGuards(editor: Editor): () => void {
   const cleanupTextMeasurementGuard = installTldrawTextMeasurementGuard(editor)
   const cleanupZoomAwareViewport = installZoomAwareViewport(editor)
+  const cleanupPlatformPermissionGuard = installTldrawPlatformPermissionGuard()
 
   return () => {
+    cleanupPlatformPermissionGuard()
     cleanupZoomAwareViewport()
     cleanupTextMeasurementGuard()
   }