fix: disappearing thumbar after win.hide() (#28366)

* fix: disappearing thumbar after win.hide()

* Add descriptive comment

shell/browser/native_window_views.cc

@@ -442,6 +442,14 @@ void NativeWindowViews::Hide() {
   if (!features::IsUsingOzonePlatform() && global_menu_bar_)
     global_menu_bar_->OnWindowUnmapped();
 #endif
+
+#if defined(OS_WIN)
+  // When the window is removed from the taskbar via win.hide(),
+  // the thumbnail buttons need to be set up again.
+  // Ensure that when the window is hidden,
+  // the taskbar host is notified that it should re-add them.
+  taskbar_host_.SetThumbarButtonsAdded(false);
+#endif
 }
 
 bool NativeWindowViews::IsVisible() {

shell/browser/ui/win/taskbar_host.cc

@@ -114,11 +114,12 @@ bool TaskbarHost::SetThumbarButtons(HWND window,
 
   // Finally add them to taskbar.
   HRESULT r;
-  if (thumbar_buttons_added_)
+  if (thumbar_buttons_added_) {
     r = taskbar_->ThumbBarUpdateButtons(window, kMaxButtonsCount,
                                         thumb_buttons);
-  else
+  } else {
     r = taskbar_->ThumbBarAddButtons(window, kMaxButtonsCount, thumb_buttons);
+  }
 
   thumbar_buttons_added_ = true;
   last_buttons_ = buttons;

shell/browser/ui/win/taskbar_host.h

@@ -60,6 +60,8 @@ class TaskbarHost {
   // Called by the window that there is a button in thumbar clicked.
   bool HandleThumbarButtonEvent(int button_id);
 
+  void SetThumbarButtonsAdded(bool added) { thumbar_buttons_added_ = added; }
+
  private:
   // Initialize the taskbar object.
   bool InitializeTaskbar();