Only Update the Scale Factor if the Scale Factor Actually Changed

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 11 matching lines @@
 #include "base/win/scoped_gdi_object.h"
 #include "base/win/windows_version.h"
 #include "ui/base/touch/touch_enabled.h"
 #include "ui/base/view_prop.h"
 #include "ui/base/win/internal_constants.h"
 #include "ui/base/win/lock_state.h"
 #include "ui/base/win/mouse_wheel_util.h"
 #include "ui/base/win/shell.h"
 #include "ui/base/win/touch_input.h"
 #include "ui/display/win/dpi.h"
+#include "ui/display/win/screen_win.h"
 #include "ui/events/event.h"
 #include "ui/events/event_utils.h"
 #include "ui/events/keycodes/keyboard_code_conversion_win.h"
 #include "ui/events/win/system_event_state_lookup.h"
 #include "ui/gfx/canvas.h"
 #include "ui/gfx/geometry/insets.h"
 #include "ui/gfx/icon_util.h"
 #include "ui/gfx/path.h"
 #include "ui/gfx/path_win.h"
 #include "ui/gfx/win/direct_manipulation.h"
@@ skipping 273 matching lines @@
 
 HWNDMessageHandler::HWNDMessageHandler(HWNDMessageHandlerDelegate* delegate)
     : msg_handled_(FALSE),
       delegate_(delegate),
       fullscreen_handler_(new FullscreenHandler),
       waiting_for_close_now_(false),
       use_system_default_icon_(false),
       restored_enabled_(false),
       current_cursor_(NULL),
       previous_cursor_(NULL),
+      dpi_(0),
       active_mouse_tracking_flags_(0),
       is_right_mouse_pressed_on_caption_(false),
       lock_updates_count_(0),
       ignore_window_pos_changes_(false),
       last_monitor_(NULL),
       is_first_nccalc_(true),
       menu_depth_(0),
       id_generator_(0),
       needs_scroll_styles_(false),
       in_size_loop_(false),
@@ skipping 1025 matching lines @@
   // receive a size notification when its initial bounds are specified at window
   // creation time.
   ClientAreaSizeChanged();
 
   delegate_->HandleCreate();
 
   windows_session_change_observer_.reset(new WindowsSessionChangeObserver(
       base::Bind(&HWNDMessageHandler::OnSessionChange,
                  base::Unretained(this))));
 
+  float scale_factor = display::win::ScreenWin::GetScaleFactorForHWND(hwnd());
+  dpi_ = display::win::GetDPIFromScalingFactor(scale_factor);
+
   // TODO(beng): move more of NWW::OnCreate here.
   return 0;
 }
 
 void HWNDMessageHandler::OnDestroy() {
   windows_session_change_observer_.reset(nullptr);
   delegate_->HandleDestroying();
   // If the window going away is a fullscreen window then remove its references
   // from the full screen window map.
   for (auto iter = fullscreen_monitor_map_.Get().begin();
@@ skipping 25 matching lines @@
   FrameTypeChanged();
   return 0;
 }
 
 LRESULT HWNDMessageHandler::OnDpiChanged(UINT msg,
                                          WPARAM w_param,
                                          LPARAM l_param) {
   if (LOWORD(w_param) != HIWORD(w_param))
     NOTIMPLEMENTED() << "Received non-square scaling factors";
 
+  // The first WM_DPICHANGED originates from EnableChildWindowDpiMessage during
+  // initialization. We don't want to propagate this as the client is already
+  // set at the current scale factor and may cause the window to display too
+  // soon. See http://crbug.com/625076.
+  int dpi = LOWORD(w_param);
+  if (dpi_ == dpi)
+    return 0;
+
+  dpi_ = dpi;
   SetBoundsInternal(gfx::Rect(*reinterpret_cast<RECT*>(l_param)), false);
   delegate_->HandleWindowScaleFactorChanged(
-      display::win::GetScalingFactorFromDPI(LOWORD(w_param)));
+      display::win::GetScalingFactorFromDPI(dpi_));
   return 0;
 }
 
 void HWNDMessageHandler::OnEnterMenuLoop(BOOL from_track_popup_menu) {
   if (menu_depth_++ == 0)
     delegate_->HandleMenuLoop(true);
 }
 
 void HWNDMessageHandler::OnEnterSizeMove() {
   // Please refer to the comments in the OnSize function about the scrollbar
@@ skipping 1330 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