fix: traffic lights not working when child windows are restored via parent window (#39225)

shell/browser/ui/cocoa/electron_ns_window_delegate.h

@@ -23,6 +23,10 @@ class NativeWindowMac;
   int level_;
   bool is_resizable_;
 
+  // Whether the window is currently minimized. Used to work
+  // around a macOS bug with child window minimization.
+  bool is_minimized_;
+
   // Only valid during a live resize.
   // Used to keep track of whether a resize is happening horizontally or
   // vertically, even if physically the user is resizing in both directions.

shell/browser/ui/cocoa/electron_ns_window_delegate.mm

@@ -55,10 +55,22 @@ using FullScreenTransitionState =
 
   // check occlusion binary flag
   if (window.occlusionState & NSWindowOcclusionStateVisible) {
-    // The app is visible
+    // There's a macOS bug where if a child window is minimized, and then both
+    // windows are restored via activation of the parent window, the child
+    // window is not properly deminiaturized. This causes traffic light bugs
+    // like the close and miniaturize buttons having no effect. We need to call
+    // deminiaturize on the child window to fix this. Unfortunately, this also
+    // hits ANOTHER bug where even after calling deminiaturize,
+    // windowDidDeminiaturize is not posted on the child window if it was
+    // incidentally restored by the parent, so we need to manually reset
+    // is_minimized_ here.
+    if (shell_->parent() && is_minimized_) {
+      shell_->Restore();
+      is_minimized_ = false;
+    }
+
     shell_->NotifyWindowShow();
   } else {
-    // The app is not visible
     shell_->NotifyWindowHide();
   }
 }
@@ -248,11 +260,15 @@ using FullScreenTransitionState =
 
 - (void)windowDidMiniaturize:(NSNotification*)notification {
   [super windowDidMiniaturize:notification];
+  is_minimized_ = true;
+
   shell_->NotifyWindowMinimize();
 }
 
 - (void)windowDidDeminiaturize:(NSNotification*)notification {
   [super windowDidDeminiaturize:notification];
+  is_minimized_ = false;
+
   shell_->AttachChildren();
   shell_->SetWindowLevel(level_);
   shell_->NotifyWindowRestore();