[WebRTC] Implement Windows ScreenDrawer to test ScreenCapturer*

webrtc/modules/desktop_capture/screen_drawer_win.cc

+/*
+ *  Copyright (c) 2016 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 <windows.h>
+
+#include <memory>
+
+#include "webrtc/modules/desktop_capture/screen_drawer.h"
+
+namespace webrtc {
+
+namespace {
+
+DesktopRect GetScreenRect() {
+  HDC hdc = GetDC(NULL);
+  DesktopRect rect = DesktopRect::MakeWH(GetDeviceCaps(hdc, HORZRES),
+                                         GetDeviceCaps(hdc, VERTRES));
+  ReleaseDC(NULL, hdc);
+  return rect;
+}
+
+HWND CreateDrawerWindow(DesktopRect rect) {
+  HWND hwnd = CreateWindowA(
+      "STATIC", "DrawerWindow", WS_POPUPWINDOW | WS_VISIBLE, rect.left(),
+      rect.top(), rect.width(), rect.height(), NULL, NULL, NULL, NULL);
+  SetForegroundWindow(hwnd);
+  return hwnd;
+}
+
+// A ScreenDrawer implementation for Windows.
+class ScreenDrawerWin : public ScreenDrawer {
+ public:
+  ScreenDrawerWin();
+  ~ScreenDrawerWin() override;
+
+  // ScreenDrawer interface.
+  DesktopRect DrawableRegion() override;
+  void DrawRectangle(DesktopRect rect, uint32_t rgba) override;
+  void Clear() override;
+
+ private:
+  const DesktopRect rect_;
+  HWND window_;
+  HDC hdc_;
+};
+
+ScreenDrawerWin::ScreenDrawerWin()
+    : ScreenDrawer(),
+      rect_(GetScreenRect()),
+      window_(CreateDrawerWindow(rect_)),
+      hdc_(GetWindowDC(window_)) {
+  // We do not need to handle any messages for the |window_|, so disable Windows
+  // process windows ghosting feature.
+  DisableProcessWindowsGhosting();
+}
+
+ScreenDrawerWin::~ScreenDrawerWin() {
+  ReleaseDC(NULL, hdc_);
+  DestroyWindow(window_);
+  // Unfortunately there is no EnableProcessWindowsGhosting() API.
+}
+
+DesktopRect ScreenDrawerWin::DrawableRegion() {
+  return rect_;
+}
+
+void ScreenDrawerWin::DrawRectangle(DesktopRect rect, uint32_t rgba) {
+  int r = (rgba & 0xff00) >> 8;
+  int g = (rgba & 0xff0000) >> 16;
+  int b = (rgba & 0xff000000) >> 24;
+  // Windows device context does not support Alpha.
+  SelectObject(hdc_, GetStockObject(DC_PEN));
+  SelectObject(hdc_, GetStockObject(DC_BRUSH));
+  SetDCBrushColor(hdc_, RGB(r, g, b));
+  SetDCPenColor(hdc_, RGB(r, g, b));
+  Rectangle(hdc_, rect.left(), rect.top(), rect.right(), rect.bottom());
+}
+
+void ScreenDrawerWin::Clear() {
+  DrawRectangle(DrawableRegion(), 0);
+}
+
+}  // namespace
+
+// static
+std::unique_ptr<ScreenDrawer> ScreenDrawer::Create() {
+  return std::unique_ptr<ScreenDrawer>(new ScreenDrawerWin());
+}
+
+}  // namespace webrtc