feat(P4B.T6): composer 'Whiteboard' button creates board + sends bubble

apps/desktop/src/lib/conversationFeatures.ts

@@ -4,6 +4,7 @@ import {
   type AttachmentHandle,
   type DecryptedMessage,
   type PollOption,
+  type WhiteboardPayload,
 } from '@chat-app/shared/chat';
 
 export type AttachmentBucket = 'media' | 'audio' | 'files';
@@ -97,6 +98,15 @@ export function createPollPayload(question: string, optionTexts: string[]): stri
   });
 }
 
+export function createWhiteboardPayload(whiteboardId: string): string {
+  const payload: WhiteboardPayload = {
+    v: 1,
+    type: 'whiteboard',
+    whiteboard_id: whiteboardId,
+  };
+  return serializeMessagePayload(payload);
+}
+
 export function summarizePollVotes(
   options: PollOption[],
   reactions: ReactionSummaryInput[],

apps/desktop/src/pages/ConversationPage.tsx

@@ -42,7 +42,13 @@ import type { DecryptedMessage } from '@chat-app/shared/chat';
 import { useAuth } from '../context/AuthContext';
 import { useCall } from '../context/CallContext';
 import { useConversationsContext } from '../context/ConversationsContext';
-import { collectConversationAttachments, createPollPayload } from '../lib/conversationFeatures';
+import {
+  collectConversationAttachments,
+  createPollPayload,
+  createWhiteboardPayload,
+} from '../lib/conversationFeatures';
+import { WhiteboardModal } from '../components/WhiteboardModal';
+import { createWhiteboard } from '@chat-app/shared/chat';
 import { compressImages } from '../lib/imageCompress';
 import { ensureInstallId } from '../lib/installId';
 import { searchCachedMessages } from '../lib/messageCache';
@@ -161,6 +167,8 @@ export function ConversationPage() {
   const [mediaDrawerOpen, setMediaDrawerOpen] = useState(false);
   const [pollDialogOpen, setPollDialogOpen] = useState(false);
   const [pollSending, setPollSending] = useState(false);
+  const [openWhiteboardId, setOpenWhiteboardId] = useState<string | null>(null);
+  const [creatingWhiteboard, setCreatingWhiteboard] = useState(false);
   const [pollError, setPollError] = useState<string | null>(null);
   const [replyTo, setReplyTo] = useState<DecryptedMessage | null>(null);
   const [forwardTarget, setForwardTarget] = useState<DecryptedMessage | null>(null);
@@ -588,6 +596,23 @@ export function ConversationPage() {
     [send, replyTo?.id, notifyStopTyping],
   );
 
+  const handleCreateWhiteboard = useCallback(async () => {
+    if (!id || creatingWhiteboard) return;
+    setCreatingWhiteboard(true);
+    try {
+      const board = await createWhiteboard(supabase, id);
+      const payload = createWhiteboardPayload(board.id);
+      await send(payload, [], replyTo?.id ?? null);
+      setReplyTo(null);
+      setStickToBottom(true);
+      setOpenWhiteboardId(board.id);
+    } catch (err: unknown) {
+      setSendError(err instanceof Error ? err.message : 'Whiteboard konnte nicht angelegt werden');
+    } finally {
+      setCreatingWhiteboard(false);
+    }
+  }, [id, creatingWhiteboard, send, replyTo?.id]);
+
   async function ingestFiles(files: File[]) {
     const compressed = await compressImages(files);
     const next: File[] = [];
@@ -981,6 +1006,16 @@ export function ConversationPage() {
           >
             <PollIcon className="h-4 w-4" />
           </button>
+          <button
+            type="button"
+            onClick={() => void handleCreateWhiteboard()}
+            disabled={creatingWhiteboard}
+            title={t('app:composer.whiteboard', { defaultValue: 'Whiteboard' })}
+            aria-label={t('app:composer.whiteboard', { defaultValue: 'Whiteboard' })}
+            className="inline-flex h-10 w-10 shrink-0 cursor-pointer items-center justify-center rounded-lg text-fg-muted transition hover:bg-surface-3 hover:text-fg focus:outline-none focus-visible:ring-2 focus-visible:ring-accent/50 disabled:cursor-not-allowed disabled:opacity-50 dark:hover:bg-[#313338]"
+          >
+            <WhiteboardIcon className="h-4 w-4" />
+          </button>
           <div className="relative">
             <button
               type="button"
@@ -1180,6 +1215,13 @@ export function ConversationPage() {
           }}
         />
       )}
+
+      {openWhiteboardId && (
+        <WhiteboardModal
+          whiteboardId={openWhiteboardId}
+          onClose={() => setOpenWhiteboardId(null)}
+        />
+      )}
     </div>
   );
 }
@@ -1459,3 +1501,13 @@ function AttachmentPreview({
     </div>
   );
 }
+
+function WhiteboardIcon(props: React.SVGProps<SVGSVGElement>) {
+  return (
+    <svg viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth={2}
+         strokeLinecap="round" strokeLinejoin="round" {...props}>
+      <rect x="3" y="4" width="18" height="13" rx="2" />
+      <path d="M8 21h8M12 17v4" />
+    </svg>
+  );
+}