Workaround windows classic theme caption rendering artifacts.

views/widget/native_widget_win.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "views/widget/native_widget_win.h"
 
 #include <dwmapi.h>
 #include <shellapi.h>
 
 #include <algorithm>
@@ skipping 1483 matching lines @@
     }
   } else if (message == WM_NCRBUTTONDOWN &&
       (w_param == HTCAPTION || w_param == HTSYSMENU)) {
     is_right_mouse_pressed_on_caption_ = true;
     // We SetMouseCapture() to ensure we only show the menu when the button
     // down and up are both on the caption. Note: this causes the button up to
     // be WM_RBUTTONUP instead of WM_NCRBUTTONUP.
     SetMouseCapture();
   }
 
-  /*
-  TODO(beng): This fixes some situations where the windows-classic appearance
-              non-client area is rendered over our custom frame, however it
-              causes mouse-releases to the non-client area to be eaten, so it
-              can't be enabled.
-  if (message == WM_NCLBUTTONDOWN) {
-    // NativeWidgetWin::OnNCLButtonDown set the message as un-handled. This
-    // normally means NativeWidgetWin::ProcessWindowMessage will pass it to
-    // DefWindowProc. Sadly, DefWindowProc for WM_NCLBUTTONDOWN does weird
-    // non-client painting, so we need to call it directly here inside a
-    // scoped update lock.
-    ScopedRedrawLock lock(this);
-    NativeWidgetWin::OnMouseRange(message, w_param, l_param);
-    DefWindowProc(GetNativeView(), WM_NCLBUTTONDOWN, w_param, l_param);
-    SetMsgHandled(TRUE);
-  }
-  */
-
   MSG msg = { hwnd(), message, w_param, l_param, 0,
               { GET_X_LPARAM(l_param), GET_Y_LPARAM(l_param) } };
   MouseEvent event(msg);
 
   if (!(event.flags() & ui::EF_IS_NON_CLIENT))
     if (tooltip_manager_.get())
       tooltip_manager_->OnMouse(message, w_param, l_param);
 
   if (event.type() == ui::ET_MOUSE_MOVED && !HasMouseCapture()) {
     // Windows only fires WM_MOUSELEAVE events if the application begins
     // "tracking" mouse events for a given HWND during WM_MOUSEMOVE events.
     // We need to call |TrackMouseEvents| to listen for WM_MOUSELEAVE.
     TrackMouseEvents((message == WM_NCMOUSEMOVE) ?
         TME_NONCLIENT | TME_LEAVE : TME_LEAVE);
   } else if (event.type() == ui::ET_MOUSE_EXITED) {
     // Reset our tracking flags so future mouse movement over this
     // NativeWidgetWin results in a new tracking session. Fall through for
     // OnMouseEvent.
     active_mouse_tracking_flags_ = 0;
   } else if (event.type() == ui::ET_MOUSEWHEEL) {
     // Reroute the mouse wheel to the window under the pointer if applicable.
     return (ui::RerouteMouseWheel(hwnd(), w_param, l_param) ||
             delegate_->OnMouseEvent(MouseWheelEvent(msg))) ? 0 : 1;
   }
 
-  SetMsgHandled(delegate_->OnMouseEvent(event));
+  bool handled = delegate_->OnMouseEvent(event);
+
+  if (!handled && message == WM_NCLBUTTONDOWN) {
+    // TODO(msw): Eliminate undesired painting, or re-evaluate this workaround.
+    // DefWindowProc for WM_NCLBUTTONDOWN does weird non-client painting, so we
+    // need to call it directly here inside a ScopedRedrawLock. This may cause
+    // other negative side-effects (ex/ stifling non-client mouse releases).
+    ScopedRedrawLock lock(this);
+    DefWindowProc(GetNativeView(), message, w_param, l_param);
+    // Update the saved window style, which may change (maximized to restored).
+    saved_window_style_ = GetWindowLong(GWL_STYLE);
+    handled = true;
+  }
+
+  SetMsgHandled(handled);
   return 0;
 }
 
 void NativeWidgetWin::OnMove(const CPoint& point) {
   // TODO(beng): move to Widget.
   GetWidget()->widget_delegate()->OnWidgetMove();
   SetMsgHandled(FALSE);
 }
 
 void NativeWidgetWin::OnMoving(UINT param, const LPRECT new_bounds) {
@@ skipping 975 matching lines @@
   return (GetKeyState(VK_LBUTTON) & 0x80) ||
     (GetKeyState(VK_RBUTTON) & 0x80) ||
     (GetKeyState(VK_MBUTTON) & 0x80) ||
     (GetKeyState(VK_XBUTTON1) & 0x80) ||
     (GetKeyState(VK_XBUTTON2) & 0x80);
 }
 
 }  // namespace internal
 
 }  // namespace views