fix: client area inset calculation when maximized for framless windows (#25052)

* adopt per monitor scale factor

* fix: client area inset calculation when maximized

* address review feedback

* pass correct glass insets to GetDwmFrameInsetsInPixels

* remove unused code

* Windows 8 and 10 use the same DWM frame calculation

Co-authored-by: Cheng Zhao <zcbenz@gmail.com>

shell/browser/ui/views/win_frame_view.cc

@@ -4,12 +4,31 @@
 
 #include "shell/browser/ui/views/win_frame_view.h"
 
+#include "base/win/windows_version.h"
 #include "shell/browser/native_window_views.h"
+#include "ui/display/win/screen_win.h"
 #include "ui/views/widget/widget.h"
 #include "ui/views/win/hwnd_util.h"
 
 namespace electron {
 
+namespace {
+
+gfx::Insets GetGlassInsets() {
+  int frame_height =
+      display::win::ScreenWin::GetSystemMetricsInDIP(SM_CYSIZEFRAME) +
+      display::win::ScreenWin::GetSystemMetricsInDIP(SM_CXPADDEDBORDER);
+
+  int frame_size =
+      base::win::GetVersion() < base::win::Version::WIN8
+          ? display::win::ScreenWin::GetSystemMetricsInDIP(SM_CXSIZEFRAME)
+          : 0;
+
+  return gfx::Insets(frame_height, frame_size, frame_size, frame_size);
+}
+
+}  // namespace
+
 const char WinFrameView::kViewClassName[] = "WinFrameView";
 
 WinFrameView::WinFrameView() {}
@@ -23,6 +42,17 @@ gfx::Rect WinFrameView::GetWindowBoundsForClientBounds(
       client_bounds);
 }
 
+gfx::Rect WinFrameView::GetBoundsForClientView() const {
+  if (window_->IsMaximized() && !window_->has_frame()) {
+    gfx::Insets insets = GetGlassInsets();
+    gfx::Rect result(width(), height());
+    result.Inset(insets);
+    return result;
+  } else {
+    return bounds();
+  }
+}
+
 int WinFrameView::NonClientHitTest(const gfx::Point& point) {
   if (window_->has_frame())
     return frame_->client_view()->NonClientHitTest(point);

shell/browser/ui/views/win_frame_view.h

@@ -16,6 +16,7 @@ class WinFrameView : public FramelessView {
   ~WinFrameView() override;
 
   // views::NonClientFrameView:
+  gfx::Rect GetBoundsForClientView() const override;
   gfx::Rect GetWindowBoundsForClientBounds(
       const gfx::Rect& client_bounds) const override;
   int NonClientHitTest(const gfx::Point& point) override;

shell/browser/ui/win/electron_desktop_window_tree_host_win.cc

@@ -4,7 +4,12 @@
 
 #include "shell/browser/ui/win/electron_desktop_window_tree_host_win.h"
 
+#include "base/win/windows_version.h"
+#include "shell/browser/ui/views/win_frame_view.h"
 #include "ui/base/win/hwnd_metrics.h"
+#include "ui/base/win/shell.h"
+#include "ui/display/win/screen_win.h"
+#include "ui/views/win/hwnd_util.h"
 
 namespace electron {
 
@@ -36,18 +41,49 @@ bool ElectronDesktopWindowTreeHostWin::HasNativeFrame() const {
   // Since we never use chromium's titlebar implementation, we can just say
   // that we use a native titlebar. This will disable the repaint locking when
   // DWM composition is disabled.
-  return true;
+  return !ui::win::IsAeroGlassEnabled();
+}
+
+bool ElectronDesktopWindowTreeHostWin::GetDwmFrameInsetsInPixels(
+    gfx::Insets* insets) const {
+  if (IsMaximized() && !native_window_view_->has_frame()) {
+    HMONITOR monitor = ::MonitorFromWindow(
+        native_window_view_->GetAcceleratedWidget(), MONITOR_DEFAULTTONEAREST);
+    int frame_height = display::win::ScreenWin::GetSystemMetricsForMonitor(
+                           monitor, SM_CYSIZEFRAME) +
+                       display::win::ScreenWin::GetSystemMetricsForMonitor(
+                           monitor, SM_CXPADDEDBORDER);
+    int frame_size = base::win::GetVersion() < base::win::Version::WIN8
+                         ? display::win::ScreenWin::GetSystemMetricsForMonitor(
+                               monitor, SM_CXSIZEFRAME)
+                         : 0;
+    insets->Set(frame_height, frame_size, frame_size, frame_size);
+    return true;
+  }
+  return false;
 }
 
 bool ElectronDesktopWindowTreeHostWin::GetClientAreaInsets(
     gfx::Insets* insets,
     HMONITOR monitor) const {
   if (IsMaximized() && !native_window_view_->has_frame()) {
-    // Windows automatically adds a standard width border to all sides when a
+    if (base::win::GetVersion() < base::win::Version::WIN8) {
-    // window is maximized.
+      // This tells Windows that most of the window is a client area, meaning
-    int frame_thickness = ui::GetFrameThickness(monitor) - 1;
+      // Chrome will draw it. Windows still fills in the glass bits because of
-    *insets = gfx::Insets(frame_thickness, frame_thickness, frame_thickness,
+      // the // DwmExtendFrameIntoClientArea call in |UpdateDWMFrame|.
-                          frame_thickness);
+      // Without this 1 pixel offset on the right and bottom:
+      //   * windows paint in a more standard way, and
+      //   * we get weird black bars at the top when maximized in multiple
+      //     monitor configurations.
+      int border_thickness = 1;
+      insets->Set(0, 0, border_thickness, border_thickness);
+    } else {
+      const int frame_thickness = ui::GetFrameThickness(monitor);
+      // Reduce the Windows non-client border size because we extend the border
+      // into our client area in UpdateDWMFrame(). The top inset must be 0 or
+      // else Windows will draw a full native titlebar outside the client area.
+      insets->Set(0, frame_thickness, frame_thickness, frame_thickness);
+    }
     return true;
   }
   return false;

shell/browser/ui/win/electron_desktop_window_tree_host_win.h

@@ -27,6 +27,7 @@ class ElectronDesktopWindowTreeHostWin
                     LRESULT* result) override;
   bool ShouldPaintAsActive() const override;
   bool HasNativeFrame() const override;
+  bool GetDwmFrameInsetsInPixels(gfx::Insets* insets) const override;
   bool GetClientAreaInsets(gfx::Insets* insets,
                            HMONITOR monitor) const override;