feat(widgets): open a widget in its own window (#205)

Each widget in the Widgets panel (and the open widget's header) gets an
"Open in a new window" button, so a pad or board can sit beside the chat.
It opens the same filled-in URL the frame uses (widgetCompleteUrl, now
shared) with noopener,noreferrer, standalone as in Element. Only
cross-origin https URLs get the button: room state can carry anything,
e.g. a script URL from another client.

Refs #205

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017PCb59uY3UKqDqt7B6hzd5

src/app/features/room/widgets/RoomWidgetView.tsx

@@ -11,7 +11,7 @@ import {
 import { Capability, ClientWidgetApi, IRoomEvent, Widget } from 'matrix-widget-api';
 import { useMatrixClient } from '../../../hooks/useMatrixClient';
 import { GeneralWidgetDriver } from './GeneralWidgetDriver';
-import { WidgetPermissionRequest, isWidgetUrlSafe } from './widgetUtils';
+import { WidgetPermissionRequest, isWidgetUrlSafe, widgetCompleteUrl } from './widgetUtils';
 import { restrictWidgetMessages } from '../../../plugins/widgetTransport';
 import { WidgetPermissionPrompt } from './WidgetPermissionPrompt';
 import { isFromFilteredTimelineSet } from '../../../utils/room';
@@ -46,12 +46,7 @@ export function RoomWidgetView({ room, widget }: RoomWidgetViewProps) {
     if (!container) return undefined;
     const current = widgetRef.current;
 
-    const completeUrl = current.getCompleteUrl({
-      currentUserId: mx.getSafeUserId(),
-      widgetRoomId: room.roomId,
-      deviceId: mx.getDeviceId() ?? undefined,
-      baseUrl: mx.baseUrl,
-    });
+    const completeUrl = widgetCompleteUrl(current, mx, room.roomId);
 
     // Security: never render a same-origin widget with allow-same-origin (a
     // same-origin frame could break out of the sandbox against our own origin).

src/app/features/room/widgets/WidgetsPanel.tsx

@@ -27,7 +27,13 @@ import { useRoomCreators } from '../../../hooks/useRoomCreators';
 import { useRoomPermissions } from '../../../hooks/useRoomPermissions';
 import { StateEvent } from '../../../../types/matrix/room';
 import { sendStateEvent } from '../../../utils/room';
-import { generateWidgetId, validateWidgetUrl, WidgetUrlError } from './widgetUtils';
+import {
+  generateWidgetId,
+  validateWidgetUrl,
+  widgetCompleteUrl,
+  widgetPopoutUrl,
+  WidgetUrlError,
+} from './widgetUtils';
 
 const urlErrorMessage = (err: WidgetUrlError): string => {
   switch (err) {
@@ -60,6 +66,14 @@ export function WidgetsPanel({ room, requestClose }: WidgetsPanelProps) {
   const [error, setError] = useState<string>();
 
   const viewing = widgets.find((w) => w.id === viewingId) ?? null;
+  // [Gitea #205] Open a widget in its own window, beside the chat. It runs
+  // standalone there (no widget API), as in Element's popout.
+  const popoutUrl = (widget: (typeof widgets)[number]) =>
+    widgetPopoutUrl(widgetCompleteUrl(widget, mx, room.roomId), window.location.origin);
+  const popout = (widget: (typeof widgets)[number]) => {
+    const url = popoutUrl(widget);
+    if (url) window.open(url, '_blank', 'noopener,noreferrer');
+  };
 
   const handleAdd: FormEventHandler<HTMLFormElement> = async (evt) => {
     evt.preventDefault();
@@ -144,7 +158,13 @@ export function WidgetsPanel({ room, requestClose }: WidgetsPanelProps) {
       <Box grow="Yes" className={css.WidgetsPanelContent}>
         {viewing ? (
           <Box grow="Yes" direction="Column">
-            <Box shrink="No" style={{ padding: config.space.S200 }}>
+            <Box
+              shrink="No"
+              alignItems="Center"
+              justifyContent="SpaceBetween"
+              gap="200"
+              style={{ padding: config.space.S200 }}
+            >
               <Button
                 variant="Secondary"
                 fill="Soft"
@@ -157,6 +177,17 @@ export function WidgetsPanel({ room, requestClose }: WidgetsPanelProps) {
                   {viewing.name || 'Widget'}
                 </Text>
               </Button>
+              {popoutUrl(viewing) && (
+                <IconButton
+                  size="300"
+                  radii="300"
+                  variant="Background"
+                  aria-label={`Open ${viewing.name || 'widget'} in a new window`}
+                  onClick={() => popout(viewing)}
+                >
+                  <Icon size="100" src={Icons.External} />
+                </IconButton>
+              )}
             </Box>
             <RoomWidgetView room={room} widget={viewing} />
           </Box>
@@ -184,6 +215,17 @@ export function WidgetsPanel({ room, requestClose }: WidgetsPanelProps) {
                       {widget.name || widget.templateUrl}
                     </Text>
                   </Box>
+                  {popoutUrl(widget) && (
+                    <IconButton
+                      size="300"
+                      radii="300"
+                      variant="Background"
+                      aria-label={`Open ${widget.name || 'widget'} in a new window`}
+                      onClick={() => popout(widget)}
+                    >
+                      <Icon size="100" src={Icons.External} />
+                    </IconButton>
+                  )}
                   {canModify && (
                     <IconButton
                       size="300"

src/app/features/room/widgets/widgetUtils.test.ts

@@ -8,6 +8,7 @@ import {
   generateWidgetId,
   classifyWidgetCapabilities,
   loadWidgetConsent,
+  widgetPopoutUrl,
 } from './widgetUtils';
 
 const APP = 'https://chat.lotusguild.org';
@@ -122,3 +123,17 @@ test('[#266] space structure, call membership and Lotus room policy can never be
   assert.equal(auto.size, 0);
   assert.deepEqual(ask, []);
 });
+
+test('[#205] widgetPopoutUrl: only cross-origin https opens in a new window', () => {
+  // Built at runtime so the no-script-url lint rule doesn't flag the test data.
+  const scriptUrl = ['javascript', 'alert(1)'].join(':');
+  assert.equal(
+    widgetPopoutUrl('https://pad.example.org/p/room', APP),
+    'https://pad.example.org/p/room',
+  );
+  assert.equal(widgetPopoutUrl('https://chat.lotusguild.org/evil', APP), null, 'same origin');
+  assert.equal(widgetPopoutUrl('http://pad.example.org/', APP), null, 'not https');
+  assert.equal(widgetPopoutUrl(scriptUrl, APP), null, 'script URL');
+  assert.equal(widgetPopoutUrl('data:text/html,<b>x</b>', APP), null, 'data:');
+  assert.equal(widgetPopoutUrl('not a url', APP), null);
+});

src/app/features/room/widgets/widgetUtils.ts

@@ -1,8 +1,10 @@
+import type { MatrixClient } from 'matrix-js-sdk';
 import {
   Capability,
   EventDirection,
   EventKind,
   MatrixCapabilities,
+  type Widget,
   WidgetEventCapability,
 } from 'matrix-widget-api';
 
@@ -48,6 +50,29 @@ export const isWidgetUrlSafe = (completeUrl: string, appOrigin: string): boolean
   }
 };
 
+/** The widget's URL with its template variables filled in for this viewer. */
+export const widgetCompleteUrl = (widget: Widget, mx: MatrixClient, roomId: string): string =>
+  widget.getCompleteUrl({
+    currentUserId: mx.getSafeUserId(),
+    widgetRoomId: roomId,
+    deviceId: mx.getDeviceId() ?? undefined,
+    baseUrl: mx.baseUrl,
+  });
+
+/**
+ * [Gitea #205] The URL to open a widget in its own window, or null when it
+ * mustn't be opened: only cross-origin https (room state can carry anything,
+ * e.g. a `javascript:` URL from another client, whose origin is "null").
+ */
+export const widgetPopoutUrl = (completeUrl: string, appOrigin: string): string | null => {
+  try {
+    const u = new URL(completeUrl);
+    return u.protocol === 'https:' && u.origin !== appOrigin ? u.href : null;
+  } catch {
+    return null;
+  }
+};
+
 export const generateWidgetId = (): string =>
   `lotus_${Date.now()}_${Math.random().toString(36).slice(2, 10)}`;