Refactor screen share picker internals

app/updateDefaultSession.ts

@@ -1,12 +1,72 @@
 // Copyright 2022 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
-import type { Session } from 'electron';
+import type { Session, DesktopCapturerSource, IpcMainEvent } from 'electron';
+import { desktopCapturer, ipcMain } from 'electron';
+import { v4 as generateUuid } from 'uuid';
+
+import OS from '../ts/util/os/osMain';
+import type { LoggerType } from '../ts/types/Logging';
+import { strictAssert } from '../ts/util/assert';
+import { type IpcResponseType } from '../ts/util/desktopCapturer';
 
 const SPELL_CHECKER_DICTIONARY_DOWNLOAD_URL = `https://updates.signal.org/desktop/hunspell_dictionaries/${process.versions.electron}/`;
 
-export function updateDefaultSession(session: Session): void {
+export function updateDefaultSession(
+  session: Session,
+  getLogger: () => LoggerType
+): void {
   session.setSpellCheckerDictionaryDownloadURL(
     SPELL_CHECKER_DICTIONARY_DOWNLOAD_URL
   );
+
+  session.setDisplayMediaRequestHandler(
+    async (request, callback) => {
+      const { frame, videoRequested, audioRequested } = request;
+
+      try {
+        strictAssert(videoRequested, 'Not requesting video');
+        strictAssert(!audioRequested, 'Requesting audio');
+
+        const sources = await desktopCapturer.getSources({
+          fetchWindowIcons: true,
+          thumbnailSize: { height: 102, width: 184 },
+          types: ['screen', 'window'],
+        });
+
+        // Wayland already shows a window/screen selection modal so we just
+        // have to go with the source that we were given.
+        if (OS.isLinux() && OS.isWaylandEnabled() && sources.length === 1) {
+          callback({ video: sources[0] });
+          return;
+        }
+
+        const id = generateUuid();
+        ipcMain.once(
+          `select-capture-sources:${id}:response`,
+          (_event: IpcMainEvent, stream: DesktopCapturerSource | undefined) => {
+            try {
+              callback({ video: stream });
+            } catch {
+              // Don't let Electron errors crash the app
+            }
+          }
+        );
+
+        frame.send('select-capture-sources', {
+          id,
+          sources,
+        } satisfies IpcResponseType);
+      } catch (error) {
+        try {
+          callback({});
+        } catch {
+          // Electron throws error here, but this is the only way to cancel the
+          // request.
+        }
+        getLogger().error('Failed to get desktopCapturer sources', error);
+      }
+    },
+    { useSystemPicker: false }
+  );
 }