fix: fullscreen windows aren't resizable on macOS (#34906)

shell/browser/native_window_mac.h

@@ -169,6 +169,7 @@ class NativeWindowMac : public NativeWindow,
   void UpdateWindowOriginalFrame();
 
   // Set the attribute of NSWindow while work around a bug of zoom button.
+  bool HasStyleMask(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

@@ -646,7 +646,7 @@ void NativeWindowMac::Unmaximize() {
 }
 
 bool NativeWindowMac::IsMaximized() {
-  if (([window_ styleMask] & NSWindowStyleMaskResizable) != 0)
+  if (HasStyleMask(NSWindowStyleMaskResizable) != 0)
     return [window_ isZoomed];
 
   NSRect rectScreen = GetAspectRatio() > 0.0
@@ -729,7 +729,7 @@ void NativeWindowMac::SetFullScreen(bool fullscreen) {
 }
 
 bool NativeWindowMac::IsFullscreen() const {
-  return [window_ styleMask] & NSWindowStyleMaskFullScreen;
+  return HasStyleMask(NSWindowStyleMaskFullScreen);
 }
 
 void NativeWindowMac::SetBounds(const gfx::Rect& bounds, bool animate) {
@@ -830,7 +830,10 @@ void NativeWindowMac::SetResizable(bool resizable) {
 }
 
 bool NativeWindowMac::IsResizable() {
-  return [window_ styleMask] & NSWindowStyleMaskResizable;
+  bool in_fs_transition =
+      fullscreen_transition_state() != FullScreenTransitionState::NONE;
+  bool has_rs_mask = HasStyleMask(NSWindowStyleMaskResizable);
+  return has_rs_mask && !IsFullscreen() && !in_fs_transition;
 }
 
 void NativeWindowMac::SetMovable(bool movable) {
@@ -846,7 +849,7 @@ void NativeWindowMac::SetMinimizable(bool minimizable) {
 }
 
 bool NativeWindowMac::IsMinimizable() {
-  return [window_ styleMask] & NSMiniaturizableWindowMask;
+  return HasStyleMask(NSWindowStyleMaskMiniaturizable);
 }
 
 void NativeWindowMac::SetMaximizable(bool maximizable) {
@@ -876,7 +879,7 @@ void NativeWindowMac::SetClosable(bool closable) {
 }
 
 bool NativeWindowMac::IsClosable() {
-  return [window_ styleMask] & NSWindowStyleMaskClosable;
+  return HasStyleMask(NSWindowStyleMaskClosable);
 }
 
 void NativeWindowMac::SetAlwaysOnTop(ui::ZOrderLevel z_order,
@@ -1391,8 +1394,7 @@ void NativeWindowMac::UpdateVibrancyRadii(bool fullscreen) {
   NSVisualEffectView* vibrantView = [window_ vibrantView];
 
   if (vibrantView != nil && !vibrancy_type_.empty()) {
-    const bool no_rounded_corner =
-        !([window_ styleMask] & NSWindowStyleMaskTitled);
+    const bool no_rounded_corner = !HasStyleMask(NSWindowStyleMaskTitled);
     if (!has_frame() && !is_modal() && !no_rounded_corner) {
       CGFloat radius;
       if (fullscreen) {
@@ -1767,6 +1769,10 @@ void NativeWindowMac::OverrideNSWindowContentView() {
   AddContentViewLayers();
 }
 
+bool NativeWindowMac::HasStyleMask(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

@@ -235,12 +235,14 @@ using FullScreenTransitionState =
 }
 
 - (void)windowWillEnterFullScreen:(NSNotification*)notification {
+  // Store resizable mask so it can be restored after exiting fullscreen.
+  is_resizable_ = shell_->HasStyleMask(NSWindowStyleMaskResizable);
+
   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);
 }