Enable cropping window capturing for Win7 when Aero is disabled.

webrtc/modules/desktop_capture/win/window_capture_utils.cc

 /*
  *  Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
 #include "webrtc/modules/desktop_capture/win/window_capture_utils.h"
 
+#include "webrtc/base/criticalsection.h"
+
 namespace webrtc {
 
 bool
 GetCroppedWindowRect(HWND window,
                      DesktopRect* cropped_rect,
                      DesktopRect* original_rect) {
   RECT rect;
   if (!GetWindowRect(window, &rect)) {
     return false;
   }
@@ skipping 13 matching lines @@
         rect.left + border.width(),
         rect.top,
         rect.right - border.width(),
         rect.bottom - border.height());
   } else {
     *cropped_rect = *original_rect;
   }
   return true;
 }
 
+bool IsAeroEnabled() {
+  typedef HRESULT (WINAPI *DwmIsCompositionEnabledFunc)(BOOL* enabled);
+
+  static rtc::GlobalLockPod lock;

[Sergey Ulanov, 2015/07/14 20:15:50]

I'm not sure it's safe to have this static inside the function. Make it global?

[jiayl2, 2015/07/14 22:25:32]

Removed

+  rtc::GlobalLockScope lock_scope(&lock);
+
+  static bool initialized = false;
+  static BOOL aero_enabled = FALSE;
+
+  if (!initialized) {
+    // Try to load dwmapi.dll dynamically since it is not available on XP.
+    HMODULE dwmapi_library = LoadLibrary(L"dwmapi.dll");
+    if (dwmapi_library) {
+      DwmIsCompositionEnabledFunc is_composition_enabled_func =
+          reinterpret_cast<DwmIsCompositionEnabledFunc>(
+              GetProcAddress(dwmapi_library, "DwmIsCompositionEnabled"));
+      is_composition_enabled_func(&aero_enabled);

[Sergey Ulanov, 2015/07/14 20:15:50]

You can store is_composition_enabled_func between IsAeroEnabled() calls, but you
should call it every time instead of remembering the result. Aero can be
enabled/disabled dynamically without restarting any applications.

[jiayl2, 2015/07/14 22:25:32]

The static method way doesn't work since it doesn't know when to free the
library.
Changed to use a object to hold the library/function.

+      FreeLibrary(dwmapi_library);
+    }
+    initialized = true;
+  }
+
+  return aero_enabled != FALSE;
+}
+
 }  // namespace webrtc