ScreenWin notifies DisplayObserver's when displays changed.

ui/gfx/screen_win.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/gfx/screen_win.h"
 
 #include <windows.h>
 
 #include "base/hash.h"
 #include "base/logging.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/win/win_util.h"
 #include "ui/gfx/display.h"
 #include "ui/gfx/win/dpi.h"
 
 namespace {
 
 MONITORINFOEX GetMonitorInfoForMonitor(HMONITOR monitor) {
   MONITORINFOEX monitor_info;
   ZeroMemory(&monitor_info, sizeof(MONITORINFOEX));
   monitor_info.cbSize = sizeof(monitor_info);
   GetMonitorInfo(monitor, &monitor_info);
   return monitor_info;
 }
 
 gfx::Display GetDisplay(MONITORINFOEX& monitor_info) {
-  // TODO(oshima): Implement Observer.
   int64 id = static_cast<int64>(
       base::Hash(base::WideToUTF8(monitor_info.szDevice)));
   gfx::Rect bounds = gfx::Rect(monitor_info.rcMonitor);
   gfx::Display display(id, bounds);
   display.set_work_area(gfx::Rect(monitor_info.rcWork));
   display.SetScaleAndBounds(gfx::win::GetDeviceScaleFactor(), bounds);
 
   DEVMODE mode;
   memset(&mode, 0, sizeof(DEVMODE));
   mode.dmSize = sizeof(DEVMODE);
@@ skipping 29 matching lines @@
   std::vector<gfx::Display>* all_displays =
       reinterpret_cast<std::vector<gfx::Display>*>(data);
   DCHECK(all_displays);
 
   MONITORINFOEX monitor_info = GetMonitorInfoForMonitor(monitor);
   gfx::Display display = GetDisplay(monitor_info);
   all_displays->push_back(display);
   return TRUE;
 }
 
+std::vector<gfx::Display> GetDisplays() {
+  std::vector<gfx::Display> displays;
+  EnumDisplayMonitors(NULL, NULL, EnumMonitorCallback,
+                      reinterpret_cast<LPARAM>(&displays));
+  return displays;
+}
+
 }  // namespace
 
 namespace gfx {
 
-ScreenWin::ScreenWin() {
+ScreenWin::ScreenWin()
+    : displays_(GetDisplays()) {
+  SingletonHwnd::GetInstance()->AddObserver(this);
 }
 
 ScreenWin::~ScreenWin() {
+  SingletonHwnd::GetInstance()->RemoveObserver(this);
 }
 
 bool ScreenWin::IsDIPEnabled() {
   return IsInHighDPIMode();
 }
 
 gfx::Point ScreenWin::GetCursorScreenPoint() {
   POINT pt;
   GetCursorPos(&pt);
   gfx::Point cursor_pos_pixels(pt);
   return gfx::win::ScreenToDIPPoint(cursor_pos_pixels);
 }
 
 gfx::NativeWindow ScreenWin::GetWindowUnderCursor() {
   POINT cursor_loc;
   HWND hwnd = GetCursorPos(&cursor_loc) ? WindowFromPoint(cursor_loc) : NULL;
   return GetNativeWindowFromHWND(hwnd);
 }
 
 gfx::NativeWindow ScreenWin::GetWindowAtScreenPoint(const gfx::Point& point) {
   gfx::Point point_in_pixels = gfx::win::DIPToScreenPoint(point);
   return GetNativeWindowFromHWND(WindowFromPoint(point_in_pixels.ToPOINT()));
 }
 
 int ScreenWin::GetNumDisplays() const {
   return GetSystemMetrics(SM_CMONITORS);
 }
 
 std::vector<gfx::Display> ScreenWin::GetAllDisplays() const {
-  std::vector<gfx::Display> all_displays;
-  EnumDisplayMonitors(NULL, NULL, EnumMonitorCallback,
-                      reinterpret_cast<LPARAM>(&all_displays));
-  return all_displays;
+  return displays_;
 }
 
 gfx::Display ScreenWin::GetDisplayNearestWindow(gfx::NativeView window) const {
   HWND window_hwnd = GetHWNDFromNativeView(window);
   if (!window_hwnd) {
     // When |window| isn't rooted to a display, we should just return the
     // default display so we get some correct display information like the
     // scaling factor.
     return GetPrimaryDisplay();
   }
@@ skipping 31 matching lines @@
   // TODO(kevers|girard): Test if these checks can be reintroduced for high-DIP
   // once more of the app is DIP-aware.
   if (!(IsInHighDPIMode() || IsHighDPIEnabled())) {
     DCHECK_EQ(GetSystemMetrics(SM_CXSCREEN), display.size().width());
     DCHECK_EQ(GetSystemMetrics(SM_CYSCREEN), display.size().height());
   }
   return display;
 }
 
 void ScreenWin::AddObserver(DisplayObserver* observer) {
-  // TODO(oshima): crbug.com/122863.
+  change_notifier_.AddObserver(observer);
 }
 
 void ScreenWin::RemoveObserver(DisplayObserver* observer) {
-  // TODO(oshima): crbug.com/122863.
+  change_notifier_.RemoveObserver(observer);
+}
+
+void ScreenWin::OnWndProc(HWND hwnd,
+                          UINT message,
+                          WPARAM wparam,
+                          LPARAM lparam) {
+  if (message != WM_DISPLAYCHANGE)
+    return;
+
+  std::vector<gfx::Display> old_displays = displays_;
+  displays_ = GetDisplays();
+
+  change_notifier_.NotifyDisplaysChanged(old_displays, displays_);
 }
 
 HWND ScreenWin::GetHWNDFromNativeView(NativeView window) const {
   NOTREACHED();
   return NULL;
 }
 
 NativeWindow ScreenWin::GetNativeWindowFromHWND(HWND hwnd) const {
   NOTREACHED();
   return NULL;
 }
 
 }  // namespace gfx