Reland of [WebRTC] A real ScreenCapturer test

webrtc/modules/desktop_capture/screen_drawer_linux.cc

Index: webrtc/modules/desktop_capture/screen_drawer_linux.cc
diff --git a/webrtc/modules/desktop_capture/screen_drawer_linux.cc b/webrtc/modules/desktop_capture/screen_drawer_linux.cc
index 2aff80b6c7ce1259f48f32ef94b12121f0256ac5..08d8195b42dd66601351d02d138e081137e8220d 100644
--- a/webrtc/modules/desktop_capture/screen_drawer_linux.cc
+++ b/webrtc/modules/desktop_capture/screen_drawer_linux.cc
@@ -13,6 +13,7 @@
 #include "webrtc/base/checks.h"
 #include "webrtc/modules/desktop_capture/screen_drawer.h"
 #include "webrtc/modules/desktop_capture/x11/shared_x_display.h"
+#include "webrtc/system_wrappers/include/sleep.h"
 
 namespace webrtc {
 
@@ -26,12 +27,12 @@ class ScreenDrawerLinux : public ScreenDrawer {
 
   // ScreenDrawer interface.
   DesktopRect DrawableRegion() override;
-  void DrawRectangle(DesktopRect rect, uint32_t rgba) override;
+  void DrawRectangle(DesktopRect rect, RgbaColor color) override;
   void Clear() override;
+  void WaitForPendingDraws() override;
 
  private:
   rtc::scoped_refptr<SharedXDisplay> display_;
-  Screen* screen_;
   int screen_num_;
   DesktopRect rect_;
   Window window_;
@@ -42,15 +43,18 @@ class ScreenDrawerLinux : public ScreenDrawer {
 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_));
+  XWindowAttributes root_attributes;
+  if (!XGetWindowAttributes(display_->display(),
+                            RootWindow(display_->display(), screen_num_),
+                            &root_attributes)) {
+    RTC_DCHECK(false) << "Failed to get root window size.";
+  }
+  window_ = XCreateSimpleWindow(
+      display_->display(), RootWindow(display_->display(), screen_num_), 0, 0,
+      root_attributes.width, root_attributes.height, 0,
+      BlackPixel(display_->display(), screen_num_),
+      BlackPixel(display_->display(), screen_num_));
   XSelectInput(display_->display(), window_, StructureNotifyMask);
   XMapWindow(display_->display(), window_);
   while (true) {
@@ -61,8 +65,23 @@ ScreenDrawerLinux::ScreenDrawerLinux() {
     }
   }
   XFlush(display_->display());
+  Window child;
+  int x, y;
+  if (!XTranslateCoordinates(display_->display(), window_,
+                             RootWindow(display_->display(), screen_num_), 0, 0,
+                             &x, &y, &child)) {
+    RTC_DCHECK(false) << "Failed to get window position.";
+  }
+  // Some window manager does not allow a window to cover two or more monitors.
+  // So if the window is on the first monitor of a two-monitor system, the
+  // second half won't be able to show up without changing configurations of WM,
+  // and its DrawableRegion() is not accurate.
+  rect_ = DesktopRect::MakeLTRB(x, y, root_attributes.width,
+                                root_attributes.height);
   context_ = DefaultGC(display_->display(), screen_num_);
   colormap_ = DefaultColormap(display_->display(), screen_num_);
+  // Wait for window animations.
+  SleepMs(200);
 }
 
 ScreenDrawerLinux::~ScreenDrawerLinux() {
@@ -74,33 +93,42 @@ 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;
+void ScreenDrawerLinux::DrawRectangle(DesktopRect rect, RgbaColor color) {
+  rect.Translate(-rect_.left(), -rect_.top());
+  XColor xcolor;
   // 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);
+  // X11 uses 16 bits for each primary color, so we need to slightly normalize
+  // a 8 bits channel to 16 bits channel, by setting the low 8 bits as its high
+  // 8 bits to avoid a mismatch of color returned by capturer.
+  xcolor.red = (color.red << 8) + color.red;
+  xcolor.green = (color.green << 8) + color.green;
+  xcolor.blue = (color.blue << 8) + color.blue;
+  xcolor.flags = DoRed | DoGreen | DoBlue;
+  XAllocColor(display_->display(), colormap_, &xcolor);
+  XSetForeground(display_->display(), context_, xcolor.pixel);
   XFillRectangle(display_->display(), window_, context_, rect.left(),
                  rect.top(), rect.width(), rect.height());
   XFlush(display_->display());
 }
 
 void ScreenDrawerLinux::Clear() {
-  DrawRectangle(DrawableRegion(), 0);
+  DrawRectangle(rect_, RgbaColor(0, 0, 0));
+}
+
+// TODO(zijiehe): Find the right signal from X11 to indicate the finish of all
+// pending paintings.
+void ScreenDrawerLinux::WaitForPendingDraws() {
+  SleepMs(50);
 }
 
 }  // namespace
 
 // static
 std::unique_ptr<ScreenDrawer> ScreenDrawer::Create() {
-  return std::unique_ptr<ScreenDrawer>(new ScreenDrawerLinux());
+  if (SharedXDisplay::CreateDefault().get()) {
+    return std::unique_ptr<ScreenDrawer>(new ScreenDrawerLinux());
+  }
+  return nullptr;
 }
 
 }  // namespace webrtc