fix: fullscreen windows aren't resizable on macOS

shell/browser/native_window_mac.h

@@ -167,6 +167,7 @@ class NativeWindowMac : public NativeWindow,
   void UpdateVibrancyRadii(bool fullscreen);
 
   // Set the attribute of NSWindow while work around a bug of zoom button.
+  bool GetStyleMask(NSUInteger flag) const;
   void SetStyleMask(bool on, NSUInteger flag);
   void SetCollectionBehavior(bool on, NSUInteger flag);
   void SetWindowLevel(int level);

shell/browser/native_window_mac.mm

@@ -641,7 +641,7 @@ void ViewDidMoveToSuperview(NSView* self, SEL _cmd) {
 }
 
 bool NativeWindowMac::IsMaximized() {
-  if (([window_ styleMask] & NSWindowStyleMaskResizable) != 0)
+  if (GetStyleMask(NSWindowStyleMaskResizable) != 0)
     return [window_ isZoomed];
 
   NSRect rectScreen = GetAspectRatio() > 0.0
@@ -715,7 +715,7 @@ void ViewDidMoveToSuperview(NSView* self, SEL _cmd) {
 }
 
 bool NativeWindowMac::IsFullscreen() const {
-  return [window_ styleMask] & NSWindowStyleMaskFullScreen;
+  return GetStyleMask(NSWindowStyleMaskFullScreen);
 }
 
 void NativeWindowMac::SetBounds(const gfx::Rect& bounds, bool animate) {
@@ -815,7 +815,10 @@ void ViewDidMoveToSuperview(NSView* self, SEL _cmd) {
 }
 
 bool NativeWindowMac::IsResizable() {
-  return [window_ styleMask] & NSWindowStyleMaskResizable;
+  bool in_fs_transition =
+      fullscreen_transition_state() != FullScreenTransitionState::NONE;
+  bool has_rs_mask = GetStyleMask(NSWindowStyleMaskResizable);
+  return has_rs_mask && !IsFullscreen() && !in_fs_transition;
 }
 
 void NativeWindowMac::SetMovable(bool movable) {
@@ -831,7 +834,7 @@ void ViewDidMoveToSuperview(NSView* self, SEL _cmd) {
 }
 
 bool NativeWindowMac::IsMinimizable() {
-  return [window_ styleMask] & NSMiniaturizableWindowMask;
+  return GetStyleMask(NSMiniaturizableWindowMask);
 }
 
 void NativeWindowMac::SetMaximizable(bool maximizable) {
@@ -861,7 +864,7 @@ void ViewDidMoveToSuperview(NSView* self, SEL _cmd) {
 }
 
 bool NativeWindowMac::IsClosable() {
-  return [window_ styleMask] & NSWindowStyleMaskClosable;
+  return GetStyleMask(NSWindowStyleMaskClosable);
 }
 
 void NativeWindowMac::SetAlwaysOnTop(ui::ZOrderLevel z_order,
@@ -1374,8 +1377,7 @@ void ViewDidMoveToSuperview(NSView* self, SEL _cmd) {
   NSVisualEffectView* vibrantView = [window_ vibrantView];
 
   if (vibrantView != nil && !vibrancy_type_.empty()) {
-    const bool no_rounded_corner =
-        !([window_ styleMask] & NSWindowStyleMaskTitled);
+    const bool no_rounded_corner = !GetStyleMask(NSWindowStyleMaskTitled);
     if (!has_frame() && !is_modal() && !no_rounded_corner) {
       CGFloat radius;
       if (fullscreen) {
@@ -1743,6 +1745,10 @@ void ViewDidMoveToSuperview(NSView* self, SEL _cmd) {
   AddContentViewLayers();
 }
 
+bool NativeWindowMac::GetStyleMask(NSUInteger flag) const {
+  return [window_ styleMask] & flag;
+}
+
 void NativeWindowMac::SetStyleMask(bool on, NSUInteger flag) {
   // Changing the styleMask of a frameless windows causes it to change size so
   // we explicitly disable resizing while setting it.

shell/browser/ui/cocoa/electron_ns_window_delegate.mm

@@ -234,12 +234,14 @@ - (void)windowDidEndLiveResize:(NSNotification*)notification {
 }
 
 - (void)windowWillEnterFullScreen:(NSNotification*)notification {
+  // Store resizable mask so it can be restored after exiting fullscreen.
+  is_resizable_ = shell_->GetStyleMask(NSResizableWindowMask);
+
   shell_->SetFullScreenTransitionState(FullScreenTransitionState::ENTERING);
 
   shell_->NotifyWindowWillEnterFullScreen();
 
-  // Setting resizable to true before entering fullscreen.
-  is_resizable_ = shell_->IsResizable();
+  // Set resizable to true before entering fullscreen.
   shell_->SetResizable(true);
 }
 

spec-main/api-browser-window-spec.ts

@@ -4208,6 +4208,16 @@ describe('BrowserWindow module', () => {
         }
       });
 
+      ifit(process.platform === 'darwin')('is false when the window is fullscreen', async () => {
+        const w = new BrowserWindow();
+
+        const enterFS = emittedOnce(w, 'enter-full-screen');
+        w.setFullScreen(true);
+        await enterFS;
+
+        expect(w.resizable).to.be.false('resizable');
+      });
+
       // On Linux there is no "resizable" property of a window.
       ifit(process.platform !== 'linux')('does affect maximizability when disabled and enabled', () => {
         const w = new BrowserWindow({ show: false });
@@ -4650,19 +4660,37 @@ describe('BrowserWindow module', () => {
     });
 
     ifdescribe(process.platform === 'darwin')('fullscreen state with resizable set', () => {
-      it('resizable flag should be set to true and restored', async () => {
+      it('resizable flag should be set to false and restored', async () => {
         const w = new BrowserWindow({ resizable: false });
+        expect(w.resizable).to.be.false('resizable');
+
         const enterFullScreen = emittedOnce(w, 'enter-full-screen');
         w.setFullScreen(true);
         await enterFullScreen;
-        expect(w.resizable).to.be.true('resizable');
+        expect(w.resizable).to.be.false('resizable');
 
         await delay();
         const leaveFullScreen = emittedOnce(w, 'leave-full-screen');
         w.setFullScreen(false);
         await leaveFullScreen;
         expect(w.resizable).to.be.false('resizable');
       });
+
+      it('default resizable flag should be restored after entering/exiting fullscreen', async () => {
+        const w = new BrowserWindow();
+        expect(w.resizable).to.be.true('resizable');
+
+        const enterFullScreen = emittedOnce(w, 'enter-full-screen');
+        w.setFullScreen(true);
+        await enterFullScreen;
+        expect(w.resizable).to.be.false('resizable');
+
+        await delay();
+        const leaveFullScreen = emittedOnce(w, 'leave-full-screen');
+        w.setFullScreen(false);
+        await leaveFullScreen;
+        expect(w.resizable).to.be.true('resizable');
+      });
     });
 
     ifdescribe(process.platform === 'darwin')('fullscreen state', () => {