Make Element Call screensharing work on desktop

src/models/Call.ts

@@ -43,6 +43,8 @@ import { WidgetMessagingStore, WidgetMessagingStoreEvent } from "../stores/widge
 import ActiveWidgetStore, { ActiveWidgetStoreEvent } from "../stores/ActiveWidgetStore";
 import PlatformPeg from "../PlatformPeg";
 import { getCurrentLanguage } from "../languageHandler";
+import DesktopCapturerSourcePicker from "../components/views/elements/DesktopCapturerSourcePicker";
+import Modal from "../Modal";
 
 const TIMEOUT_MS = 16000;
 
@@ -639,10 +641,6 @@ export class ElementCall extends Call {
             baseUrl: client.baseUrl,
             lang: getCurrentLanguage().replace("_", "-"),
         });
-        // Currently, the screen-sharing support is the same is it is for Jitsi
-        if (!PlatformPeg.get().supportsJitsiScreensharing()) {
-            params.append("hideScreensharing", "");
-        }
         url.hash = `#?${params.toString()}`;
 
         // To use Element Call without touching room state, we create a virtual
@@ -818,6 +816,7 @@ export class ElementCall extends Call {
         this.messaging!.on(`action:${ElementWidgetActions.HangupCall}`, this.onHangup);
         this.messaging!.on(`action:${ElementWidgetActions.TileLayout}`, this.onTileLayout);
         this.messaging!.on(`action:${ElementWidgetActions.SpotlightLayout}`, this.onSpotlightLayout);
+        this.messaging!.on(`action:${ElementWidgetActions.Screenshare}`, this.onScreenshare);
     }
 
     protected async performDisconnection(): Promise<void> {
@@ -951,4 +950,20 @@ export class ElementCall extends Call {
         this.layout = Layout.Spotlight;
         await this.messaging!.transport.reply(ev.detail, {}); // ack
     };
+
+    private onScreenshare = async (ev: CustomEvent<IWidgetApiRequest>) => {
+        ev.preventDefault();
+
+        if (PlatformPeg.get().supportsDesktopCapturer()) {
+            const { finished } = Modal.createDialog(DesktopCapturerSourcePicker);
+            const [source] = await finished;
+
+            await this.messaging!.transport.reply(ev.detail, {
+                failed: !source,
+                desktopCapturerSourceId: source,
+            });
+        } else {
+            await this.messaging!.transport.reply(ev.detail, {});
+        }
+    };
 }

src/stores/widgets/ElementWidgetActions.ts

@@ -29,6 +29,7 @@ export enum ElementWidgetActions {
     // Actions for switching layouts
     TileLayout = "io.element.tile_layout",
     SpotlightLayout = "io.element.spotlight_layout",
+    Screenshare = "io.element.screenshare",
 
     OpenIntegrationManager = "integration_manager_open",