[WebRTC] Implement Windows ScreenDrawer to test ScreenCapturer*

webrtc/modules/desktop_capture/screen_drawer_linux.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 <memory>
+
+#include "webrtc/base/checks.h"
+#include "webrtc/modules/desktop_capture/screen_drawer.h"
+#include "webrtc/modules/desktop_capture/x11/shared_x_display.h"
+
+namespace webrtc {
+
+namespace {
+
+// A ScreenDrawer implementation for X11.
+class ScreenDrawerLinux : public ScreenDrawer {
+ public:
+  ScreenDrawerLinux();
+  ~ScreenDrawerLinux() override;
+
+  // ScreenDrawer interface.
+  DesktopRect DrawableRegion() override;
+  void DrawRectangle(DesktopRect rect, uint32_t rgba) override;
+  void Clear() override;
+
+ private:
+  rtc::scoped_refptr<SharedXDisplay> display_;
+  Screen* screen_;
+  int screen_num_;
+  DesktopRect rect_;
+  Window window_;
+  GC context_;
+  Colormap colormap_;
+};
+
+ScreenDrawerLinux::ScreenDrawerLinux() {
+  display_ = SharedXDisplay::CreateDefault();
+  RTC_CHECK(display_.get());
+  screen_ = DefaultScreenOfDisplay(display_->display());
+  RTC_CHECK(screen_);
+  screen_num_ = DefaultScreen(display_->display());
+  rect_ = DesktopRect::MakeWH(screen_->width, screen_->height);
+  window_ = XCreateSimpleWindow(display_->display(),
+                                RootWindow(display_->display(), screen_num_), 0,
+                                0, rect_.width(), rect_.height(), 0,
+                                BlackPixel(display_->display(), screen_num_),
+                                BlackPixel(display_->display(), screen_num_));
+  XSelectInput(display_->display(), window_, StructureNotifyMask);
+  XMapWindow(display_->display(), window_);
+  while (true) {
+    XEvent event;
+    XNextEvent(display_->display(), &event);
+    if (event.type == MapNotify) {
+      break;
+    }
+  }
+  XFlush(display_->display());
+  context_ = DefaultGC(display_->display(), screen_num_);
+  colormap_ = DefaultColormap(display_->display(), screen_num_);
+}
+
+ScreenDrawerLinux::~ScreenDrawerLinux() {
+  XUnmapWindow(display_->display(), window_);
+  XDestroyWindow(display_->display(), window_);
+}
+
+DesktopRect ScreenDrawerLinux::DrawableRegion() {
+  return rect_;
+}
+
+void ScreenDrawerLinux::DrawRectangle(DesktopRect rect, uint32_t rgba) {
+  int r = (rgba & 0xff00) >> 8;
+  int g = (rgba & 0xff0000) >> 16;
+  int b = (rgba & 0xff000000) >> 24;
+  // X11 does not support Alpha.
+  XColor color;
+  // X11 uses 16 bits for each primary color.
+  color.red = r * 256;
+  color.green = g * 256;
+  color.blue = b * 256;
+  color.flags = DoRed | DoGreen | DoBlue;
+  XAllocColor(display_->display(), colormap_, &color);
+  XSetForeground(display_->display(), context_, color.pixel);
+  XFillRectangle(display_->display(), window_, context_, rect.left(),
+                 rect.top(), rect.width(), rect.height());
+  XFlush(display_->display());
+}
+
+void ScreenDrawerLinux::Clear() {
+  DrawRectangle(DrawableRegion(), 0);
+}
+
+}  // namespace
+
+// static
+std::unique_ptr<ScreenDrawer> ScreenDrawer::Create() {
+  return std::unique_ptr<ScreenDrawer>(new ScreenDrawerLinux());
+}
+
+}  // namespace webrtc