fix(desktop): handle macOS back and forward gestures

apps/desktop/src/window/DesktopWindow.test.ts

@@ -78,6 +78,12 @@ function makeFakeBrowserWindow() {
       zoomLevel = level;
     }),
     isLoadingMainFrame: vi.fn(() => false),
+    navigationHistory: {
+      canGoBack: vi.fn(() => true),
+      canGoForward: vi.fn(() => true),
+      goBack: vi.fn(),
+      goForward: vi.fn(),
+    },
     on: vi.fn((eventName: string, listener: (...args: readonly unknown[]) => void) => {
       webContentsListeners.set(eventName, listener);
     }),
@@ -136,6 +142,7 @@ function makeFakeBrowserWindow() {
     reload: webContents.reload,
     reloadIgnoringCache: webContents.reloadIgnoringCache,
     toggleDevTools: webContents.toggleDevTools,
+    navigationHistory: webContents.navigationHistory,
     send: webContents.send,
     setZoomLevel: webContents.setZoomLevel,
     setWindowButtonPosition: window.setWindowButtonPosition,
@@ -895,6 +902,39 @@ describe("DesktopWindow", () => {
     }),
   );
 
+  it.effect("maps macOS horizontal swipes to available history navigation", () =>
+    Effect.gen(function* () {
+      const fakeWindow = makeFakeBrowserWindow();
+      const createCount = yield* Ref.make(0);
+      const mainWindow = yield* Ref.make<Option.Option<Electron.BrowserWindow>>(Option.none());
+      const layer = layerTest({ window: fakeWindow.window, createCount, mainWindow });
+
+      yield* Effect.gen(function* () {
+        const desktopWindow = yield* DesktopWindow.DesktopWindow;
+        yield* desktopWindow.handleBackendReady(new URL("http://127.0.0.1:3773"));
+        const swipe = fakeWindow.windowListeners.get("swipe");
+        assert.isDefined(swipe);
+        if (!swipe) return;
+        const history = fakeWindow.navigationHistory;
+
+        swipe({}, "left");
+        assert.equal(history.goBack.mock.calls.length, 1);
+        assert.equal(history.goForward.mock.calls.length, 0);
+        swipe({}, "right");
+        assert.equal(history.goForward.mock.calls.length, 1);
+
+        swipe({}, "up");
+        swipe({}, "down");
+        history.canGoBack.mockReturnValue(false);
+        history.canGoForward.mockReturnValue(false);
+        swipe({}, "left");
+        swipe({}, "right");
+        assert.equal(history.goBack.mock.calls.length, 1);
+        assert.equal(history.goForward.mock.calls.length, 1);
+      }).pipe(Effect.provide(layer));
+    }),
+  );
+
   it.effect("persists the current main window bounds before the window closes", () =>
     Effect.gen(function* () {
       const fakeWindow = makeFakeBrowserWindow();

apps/desktop/src/window/DesktopWindow.ts

@@ -673,6 +673,12 @@ export const make = Effect.gen(function* () {
     });
 
     if (environment.platform === "darwin") {
+      // Mouse drivers can deliver Back/Forward as macOS swipe gestures instead of buttons.
+      window.on("swipe", (_event, direction) => {
+        const history = window.webContents.navigationHistory;
+        if (direction === "left" && history.canGoBack()) history.goBack();
+        else if (direction === "right" && history.canGoForward()) history.goForward();
+      });
       window.on("enter-full-screen", () => {
         window.webContents.send(WINDOW_FULLSCREEN_STATE_CHANNEL, true);
       });