Fix embedded Element Call screen sharing

src/models/Call.ts

@@ -816,7 +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);
+        this.messaging!.on(`action:${ElementWidgetActions.ScreenshareRequest}`, this.onScreenshareRequest);
     }
 
     protected async performDisconnection(): Promise<void> {
@@ -832,7 +832,7 @@ export class ElementCall extends Call {
         this.messaging!.off(`action:${ElementWidgetActions.HangupCall}`, this.onHangup);
         this.messaging!.off(`action:${ElementWidgetActions.TileLayout}`, this.onTileLayout);
         this.messaging!.off(`action:${ElementWidgetActions.SpotlightLayout}`, this.onSpotlightLayout);
-        this.messaging!.off(`action:${ElementWidgetActions.Screenshare}`, this.onSpotlightLayout);
+        this.messaging!.off(`action:${ElementWidgetActions.ScreenshareRequest}`, this.onScreenshareRequest);
         super.setDisconnected();
     }
 
@@ -952,19 +952,24 @@ export class ElementCall extends Call {
         await this.messaging!.transport.reply(ev.detail, {}); // ack
     };
 
-    private onScreenshare = async (ev: CustomEvent<IWidgetApiRequest>) => {
+    private onScreenshareRequest = async (ev: CustomEvent<IWidgetApiRequest>) => {
         ev.preventDefault();
 
         if (PlatformPeg.get().supportsDesktopCapturer()) {
+            await this.messaging!.transport.reply(ev.detail, { pending: true });
+
             const { finished } = Modal.createDialog(DesktopCapturerSourcePicker);
             const [source] = await finished;
 
-            await this.messaging!.transport.reply(ev.detail, {
-                failed: !source,
-                desktopCapturerSourceId: source,
-            });
+            if (source) {
+                await this.messaging!.transport.send(ElementWidgetActions.ScreenshareStart, {
+                    desktopCapturerSourceId: source,
+                });
+            } else {
+                await this.messaging!.transport.send(ElementWidgetActions.ScreenshareStop, {});
+            }
         } else {
-            await this.messaging!.transport.reply(ev.detail, {});
+            await this.messaging!.transport.reply(ev.detail, { pending: false });
         }
     };
 }

src/stores/widgets/ElementWidgetActions.ts

@@ -26,10 +26,23 @@ export enum ElementWidgetActions {
     MuteVideo = "io.element.mute_video",
     UnmuteVideo = "io.element.unmute_video",
     StartLiveStream = "im.vector.start_live_stream",
+
+    // Element Call -> host requesting to start a screenshare
+    // (ie. expects a ScreenshareStart once the user has picked a source)
+    // replies with { pending } where pending is true if the host has asked
+    // the user to choose a window and false if not (ie. if the host isn't
+    // running within Electron)
+    ScreenshareRequest = "io.element.screenshare_request",
+    // host -> Element Call telling EC to start screen sharing with
+    // the given source
+    ScreenshareStart = "io.element.screenshare_start",
+    // host -> Element Call telling EC to stop screen sharing, or that
+    // the user cancelled when selecting a source after a ScreenshareRequest
+    ScreenshareStop = "io.element.screenshare_stop",
+
     // Actions for switching layouts
     TileLayout = "io.element.tile_layout",
     SpotlightLayout = "io.element.spotlight_layout",
-    Screenshare = "io.element.screenshare",
 
     OpenIntegrationManager = "integration_manager_open",
 

test/models/Call-test.ts

@@ -820,19 +820,25 @@ describe("ElementCall", () => {
                 await call.connect();
 
                 messaging.emit(
-                    `action:${ElementWidgetActions.Screenshare}`,
+                    `action:${ElementWidgetActions.ScreenshareRequest}`,
                     new CustomEvent("widgetapirequest", { detail: {} }),
                 );
 
-                waitFor(() => {
+                await waitFor(() => {
                     expect(messaging!.transport.reply).toHaveBeenCalledWith(
                         expect.objectContaining({}),
-                        expect.objectContaining({ desktopCapturerSourceId: sourceId }),
+                        expect.objectContaining({ pending: true }),
+                    );
+                });
+
+                await waitFor(() => {
+                    expect(messaging!.transport.send).toHaveBeenCalledWith(
+                        "io.element.screenshare_start", expect.objectContaining({ desktopCapturerSourceId: sourceId }),
                     );
                 });
             });
 
-            it("passes failed if we couldn't get a source id", async () => {
+            it("sends ScreenshareStop if we couldn't get a source id", async () => {
                 jest.spyOn(Modal, "createDialog").mockReturnValue(
                     { finished: new Promise((r) => r([null])) } as IHandle<any[]>,
                 );
@@ -841,32 +847,38 @@ describe("ElementCall", () => {
                 await call.connect();
 
                 messaging.emit(
-                    `action:${ElementWidgetActions.Screenshare}`,
+                    `action:${ElementWidgetActions.ScreenshareRequest}`,
                     new CustomEvent("widgetapirequest", { detail: {} }),
                 );
 
-                waitFor(() => {
+                await waitFor(() => {
                     expect(messaging!.transport.reply).toHaveBeenCalledWith(
                         expect.objectContaining({}),
-                        expect.objectContaining({ failed: true }),
+                        expect.objectContaining({ pending: true }),
+                    );
+                });
+
+                await waitFor(() => {
+                    expect(messaging!.transport.send).toHaveBeenCalledWith(
+                        "io.element.screenshare_stop", expect.objectContaining({ }),
                     );
                 });
             });
 
-            it("passes an empty object if we don't support desktop capturer", async () => {
+            it("replies with pending: false if we don't support desktop capturer", async () => {
                 jest.spyOn(PlatformPeg.get(), "supportsDesktopCapturer").mockReturnValue(false);
 
                 await call.connect();
 
                 messaging.emit(
-                    `action:${ElementWidgetActions.Screenshare}`,
+                    `action:${ElementWidgetActions.ScreenshareRequest}`,
                     new CustomEvent("widgetapirequest", { detail: {} }),
                 );
 
-                waitFor(() => {
+                await waitFor(() => {
                     expect(messaging!.transport.reply).toHaveBeenCalledWith(
                         expect.objectContaining({}),
-                        expect.objectContaining({}),
+                        expect.objectContaining({ pending: false }),
                     );
                 });
             });