Restore maximized window position after detaching display.

ui/views/win/hwnd_message_handler.cc

 // Copyright (c) 2012 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 "ui/views/win/hwnd_message_handler.h"
 
 #include <dwmapi.h>
 #include <oleacc.h>
 #include <shellapi.h>
 #include <tchar.h>
@@ skipping 1613 matching lines @@
       GetProcAddress(GetModuleHandleA("user32.dll"), "GetPointerType"));
   if (get_pointer_type && get_pointer_type(pointer_id, &pointer_type) &&
       pointer_type == PT_TOUCHPAD)
     return PA_NOACTIVATE;
   SetMsgHandled(FALSE);
   return -1;
 }
 
 void HWNDMessageHandler::OnMove(const gfx::Point& point) {
   delegate_->HandleMove();
+
+  RECT window_rect;

[sky, 2016/09/29 18:16:23]

Would it make more sense for this to be in OnWindowPosChanging?

+  HMONITOR monitor;
+  gfx::Rect monitor_rect, work_area;
+  if (!GetParent(hwnd()) && IsMaximized() &&
+      GetWindowRect(hwnd(), &window_rect) &&
+      GetMonitorAndRects(window_rect, &monitor, &monitor_rect, &work_area)) {
+    gfx::Rect expected_window_bounds = work_area;
+
+    // Windows automatically adds a standard width border to all sides when a
+    // window is maximized. We should take this into account.
+    gfx::Insets client_area_insets;
+    if (GetClientAreaInsets(&client_area_insets))
+      expected_window_bounds.Inset(client_area_insets.Scale(-1));
+
+    if (GetWindowBoundsInScreen() != expected_window_bounds) {
+      // Sometimes Windows incorrectly changes bounds of maximized windows after
+      // attaching or detaching additional displays. In this case user can see
+      // non-client area of the window (that should be hidden in normal case).
+      // This workaround code restores window position if problem occurs.
+      SetWindowPos(hwnd(), NULL,
+                   expected_window_bounds.x(),
+                   expected_window_bounds.y(),
+                   expected_window_bounds.width(),
+                   expected_window_bounds.height(),
+                   SWP_NOACTIVATE | SWP_NOZORDER);
+    }
+  }
+
   SetMsgHandled(FALSE);
 }
 
 void HWNDMessageHandler::OnMoving(UINT param, const RECT* new_bounds) {
   delegate_->HandleMove();
 }
 
 LRESULT HWNDMessageHandler::OnNCActivate(UINT message,
                                          WPARAM w_param,
                                          LPARAM l_param) {
@@ skipping 1066 matching lines @@
   MONITORINFO monitor_info = {sizeof(monitor_info)};
   GetMonitorInfo(MonitorFromWindow(hwnd(), MONITOR_DEFAULTTOPRIMARY),
                  &monitor_info);
   gfx::Rect shrunk_rect(monitor_info.rcMonitor);
   shrunk_rect.set_height(shrunk_rect.height() - 1);
   background_fullscreen_hack_ = true;
   SetBoundsInternal(shrunk_rect, false);
 }
 
 }  // namespace views