feat: add `BrowserWindow.isOccluded()` (#38982)

feat: add BrowserWindow.isOccluded()

docs/api/browser-window.md

@@ -644,6 +644,14 @@ Shows the window but doesn't focus on it.
 
 Hides the window.
 
+#### `win.isOccluded()`
+
+Returns `boolean` - Whether the window is covered by other windows.
+
+On macOS, a `BrowserWindow` is occluded if the entire window is obscured by other windows. A completely transparent window may also be considered non-occluded. See [docs](https://developer.apple.com/documentation/appkit/nswindowocclusionstate?language=objc) for more details.
+
+On Windows and Linux, a window is occluded if it or one of its descendants is visible, and all visible windows have their bounds completely covered by fully opaque windows. A window is considered "fully opaque" if it is visible, it is not transparent, and its combined opacity is 1. See [Chromium Source](https://source.chromium.org/chromium/chromium/src/+/refs/heads/main:ui/aura/window.h;l=124-151;drc=7d2d8ccab2b68fbbfc5e1611d45bd4ecf87090b8) for more details.
+
 #### `win.isVisible()`
 
 Returns `boolean` - Whether the window is visible to the user in the foreground of the app.

shell/browser/api/electron_api_base_window.cc

@@ -355,6 +355,10 @@ bool BaseWindow::IsVisible() const {
   return window_->IsVisible();
 }
 
+bool BaseWindow::IsOccluded() const {
+  return window_->IsOccluded();
+}
+
 bool BaseWindow::IsEnabled() const {
   return window_->IsEnabled();
 }
@@ -1086,6 +1090,7 @@ void BaseWindow::BuildPrototype(v8::Isolate* isolate,
       .SetMethod("showInactive", &BaseWindow::ShowInactive)
       .SetMethod("hide", &BaseWindow::Hide)
       .SetMethod("isVisible", &BaseWindow::IsVisible)
+      .SetMethod("isOccluded", &BaseWindow::IsOccluded)
       .SetMethod("isEnabled", &BaseWindow::IsEnabled)
       .SetMethod("setEnabled", &BaseWindow::SetEnabled)
       .SetMethod("maximize", &BaseWindow::Maximize)

shell/browser/api/electron_api_base_window.h

@@ -98,6 +98,7 @@ class BaseWindow : public gin_helper::TrackableObject<BaseWindow>,
   void ShowInactive();
   void Hide();
   bool IsVisible() const;
+  bool IsOccluded() const;
   bool IsEnabled() const;
   void SetEnabled(bool enable);
   void Maximize();

shell/browser/native_window.h

@@ -87,6 +87,7 @@ class NativeWindow : public base::SupportsUserData,
   virtual void Show() = 0;
   virtual void ShowInactive() = 0;
   virtual void Hide() = 0;
+  virtual bool IsOccluded() const = 0;
   virtual bool IsVisible() const = 0;
   virtual bool IsEnabled() const = 0;
   virtual void SetEnabled(bool enable) = 0;

shell/browser/native_window_mac.h

@@ -44,6 +44,7 @@ class NativeWindowMac : public NativeWindow,
   void Show() override;
   void ShowInactive() override;
   void Hide() override;
+  bool IsOccluded() const override;
   bool IsVisible() const override;
   bool IsEnabled() const override;
   void SetEnabled(bool enable) override;

shell/browser/native_window_mac.mm

@@ -561,9 +561,12 @@ void NativeWindowMac::Hide() {
   [window_ orderOut:nil];
 }
 
+bool NativeWindowMac::IsOccluded() const {
+  return !([window_ occlusionState] & NSWindowOcclusionStateVisible);
+}
+
 bool NativeWindowMac::IsVisible() const {
-  bool occluded = [window_ occlusionState] == NSWindowOcclusionStateVisible;
-  return [window_ isVisible] && !occluded && !IsMinimized();
+  return [window_ isVisible] && !IsMinimized();
 }
 
 bool NativeWindowMac::IsEnabled() const {

shell/browser/native_window_views.cc

@@ -562,6 +562,14 @@ void NativeWindowViews::Hide() {
 #endif
 }
 
+bool NativeWindowViews::IsOccluded() const {
+  if (!GetNativeWindow())
+    return false;
+  auto occlusion_state =
+      GetNativeWindow()->GetHost()->GetNativeWindowOcclusionState();
+  return occlusion_state == aura::Window::OcclusionState::OCCLUDED;
+}
+
 bool NativeWindowViews::IsVisible() const {
 #if BUILDFLAG(IS_WIN)
   // widget()->IsVisible() calls ::IsWindowVisible, which returns non-zero if a

shell/browser/native_window_views.h

@@ -56,6 +56,7 @@ class NativeWindowViews : public NativeWindow,
   void Hide() override;
   bool IsVisible() const override;
   bool IsEnabled() const override;
+  bool IsOccluded() const override;
   void SetEnabled(bool enable) override;
   void Maximize() override;
   void Unmaximize() override;

spec/api-browser-window-spec.ts

@@ -4164,6 +4164,65 @@ describe('BrowserWindow module', () => {
     });
   });
 
+  describe('BrowserWindow.isOccluded()', () => {
+    afterEach(closeAllWindows);
+
+    it('returns false for a visible window', async () => {
+      const w = new BrowserWindow({ show: false });
+
+      const shown = once(w, 'show');
+      w.show();
+      await shown;
+
+      expect(w.isOccluded()).to.be.false('window is occluded');
+    });
+
+    it('returns false when the window is only partially obscured', async () => {
+      const w1 = new BrowserWindow({ width: 400, height: 400 });
+      const w2 = new BrowserWindow({ show: false, width: 450, height: 450 });
+
+      const focused = once(w2, 'focus');
+      w2.show();
+      await focused;
+
+      await setTimeout(1000);
+      expect(w1.isOccluded()).to.be.true('window is not occluded');
+
+      const pos = w2.getPosition();
+      const move = once(w2, 'move');
+      w2.setPosition(pos[0] - 100, pos[1]);
+      await move;
+
+      await setTimeout(1000);
+      expect(w1.isOccluded()).to.be.false('window is occluded');
+    });
+
+    // FIXME: this test fails on Linux CI due to windowing issues.
+    ifit(process.platform !== 'linux')('returns false for a visible window covered by a transparent window', async () => {
+      const w1 = new BrowserWindow({ width: 200, height: 200 });
+      const w2 = new BrowserWindow({ show: false, transparent: true, frame: false });
+
+      const focused = once(w2, 'focus');
+      w2.show();
+      await focused;
+
+      await setTimeout(1000);
+      expect(w1.isOccluded()).to.be.false('window is occluded');
+    });
+
+    it('returns true for an obscured window', async () => {
+      const w1 = new BrowserWindow({ width: 200, height: 200 });
+      const w2 = new BrowserWindow({ show: false });
+
+      const focused = once(w2, 'focus');
+      w2.show();
+      await focused;
+
+      await setTimeout(1000);
+      expect(w1.isOccluded()).to.be.true('visible window');
+    });
+  });
+
   // TODO(codebytere): figure out how to make these pass in CI on Windows.
   ifdescribe(process.platform !== 'win32')('document.visibilityState/hidden', () => {
     afterEach(closeAllWindows);