fix: adjust window size in NCCALCSIZE instead of adding insets (#19883)

shell/browser/native_window_views_win.cc

@@ -239,6 +239,15 @@ int GetAppbarAutohideEdges(HWND hwnd) {
   return edges;
 }
 
+void TriggerNCCalcSize(HWND hwnd) {
+  RECT rcClient;
+  ::GetWindowRect(hwnd, &rcClient);
+
+  ::SetWindowPos(hwnd, NULL, rcClient.left, rcClient.top,
+                 rcClient.right - rcClient.left, rcClient.bottom - rcClient.top,
+                 SWP_FRAMECHANGED);
+}
+
 }  // namespace
 
 std::set<NativeWindowViews*> NativeWindowViews::forwarding_windows_;
@@ -369,8 +378,12 @@ bool NativeWindowViews::PreHandleMSG(UINT message,
         // https://blogs.msdn.microsoft.com/wpfsdk/2008/09/08/custom-window-chrome-in-wpf/
         DefWindowProcW(GetAcceleratedWidget(), WM_NCCALCSIZE, w_param, l_param);
 
-        params->rgrc[0] = PROPOSED;
+        if (last_window_state_ == ui::SHOW_STATE_MAXIMIZED) {
-        params->rgrc[1] = BEFORE;
+          params->rgrc[0].top = 0;
+        } else {
+          params->rgrc[0] = PROPOSED;
+          params->rgrc[1] = BEFORE;
+        }
 
         return true;
       } else {
@@ -453,26 +466,15 @@ void NativeWindowViews::HandleSizeEvent(WPARAM w_param, LPARAM l_param) {
   // window state and notify the user accordingly.
   switch (w_param) {
     case SIZE_MAXIMIZED: {
-      // Frameless maximized windows are size compensated by Windows for a
-      // border that's not actually there, so we must conter-compensate.
-      // https://blogs.msdn.microsoft.com/wpfsdk/2008/09/08/custom-window-chrome-in-wpf/
-      if (!has_frame()) {
-        float scale_factor = display::win::ScreenWin::GetScaleFactorForHWND(
-            GetAcceleratedWidget());
-
-        int border =
-            GetSystemMetrics(SM_CXFRAME) + GetSystemMetrics(SM_CXPADDEDBORDER);
-        if (!thick_frame_) {
-          border -= GetSystemMetrics(SM_CXBORDER);
-        }
-        root_view_->SetInsets(gfx::Insets(border).Scale(1.0f / scale_factor));
-      }
-
       last_window_state_ = ui::SHOW_STATE_MAXIMIZED;
       if (consecutive_moves_) {
         last_normal_bounds_ = last_normal_bounds_before_move_;
       }
 
+      if (!has_frame()) {
+        TriggerNCCalcSize(GetAcceleratedWidget());
+      }
+
       NotifyWindowMaximize();
       break;
     }
@@ -497,8 +499,12 @@ void NativeWindowViews::HandleSizeEvent(WPARAM w_param, LPARAM l_param) {
         switch (last_window_state_) {
           case ui::SHOW_STATE_MAXIMIZED:
             last_window_state_ = ui::SHOW_STATE_NORMAL;
-            root_view_->SetInsets(gfx::Insets(0));
             NotifyWindowUnmaximize();
+
+            if (!has_frame()) {
+              TriggerNCCalcSize(GetAcceleratedWidget());
+            }
+
             break;
           case ui::SHOW_STATE_MINIMIZED:
             if (IsFullscreen()) {

shell/browser/ui/views/root_view.cc

@@ -176,18 +176,14 @@ void RootView::Layout() {
     return;
 
   const auto menu_bar_bounds =
-      menu_bar_visible_
+      menu_bar_visible_ ? gfx::Rect(0, 0, size().width(), kMenuBarHeight)
-          ? gfx::Rect(insets_.left(), insets_.top(),
+                        : gfx::Rect();
-                      size().width() - insets_.width(), kMenuBarHeight)
-          : gfx::Rect();
   if (menu_bar_)
     menu_bar_->SetBoundsRect(menu_bar_bounds);
 
   window_->content_view()->SetBoundsRect(
-      gfx::Rect(insets_.left(),
+      gfx::Rect(0, menu_bar_visible_ ? menu_bar_bounds.bottom() : 0,
-                menu_bar_visible_ ? menu_bar_bounds.bottom() : insets_.top(),
+                size().width(), size().height() - menu_bar_bounds.height()));
-                size().width() - insets_.width(),
-                size().height() - menu_bar_bounds.height() - insets_.height()));
 }
 
 gfx::Size RootView::GetMinimumSize() const {
@@ -224,11 +220,4 @@ void RootView::UnregisterAcceleratorsWithFocusManager() {
   focus_manager->UnregisterAccelerators(this);
 }
 
-void RootView::SetInsets(const gfx::Insets& insets) {
-  if (insets != insets_) {
-    insets_ = insets;
-    Layout();
-  }
-}
-
 }  // namespace electron

shell/browser/ui/views/root_view.h

@@ -40,8 +40,6 @@ class RootView : public views::View {
   // Register/Unregister accelerators supported by the menu model.
   void RegisterAcceleratorsWithFocusManager(AtomMenuModel* menu_model);
   void UnregisterAcceleratorsWithFocusManager();
-  void SetInsets(const gfx::Insets& insets);
-  gfx::Insets insets() const { return insets_; }
 
   // views::View:
   void Layout() override;
@@ -59,8 +57,6 @@ class RootView : public views::View {
   bool menu_bar_visible_ = false;
   bool menu_bar_alt_pressed_ = false;
 
-  gfx::Insets insets_;
-
   // Map from accelerator to menu item's command id.
   accelerator_util::AcceleratorTable accelerator_table_;