[WebRTC] A real ScreenCapturer test

webrtc/modules/desktop_capture/screen_drawer_win.cc

Index: webrtc/modules/desktop_capture/screen_drawer_win.cc
diff --git a/webrtc/modules/desktop_capture/screen_drawer_win.cc b/webrtc/modules/desktop_capture/screen_drawer_win.cc
index 061a40539e1cb72091347bf1b743b2315982e99c..52a6df3bee40d2a86253c57feae1e7f9f9948ac9 100644
--- a/webrtc/modules/desktop_capture/screen_drawer_win.cc
+++ b/webrtc/modules/desktop_capture/screen_drawer_win.cc
@@ -13,6 +13,7 @@
 #include <memory>
 
 #include "webrtc/modules/desktop_capture/screen_drawer.h"
+#include "webrtc/system_wrappers/include/sleep.h"
 
 namespace webrtc {
 
@@ -34,6 +35,11 @@ HWND CreateDrawerWindow(DesktopRect rect) {
   return hwnd;
 }
 
+COLORREF ColorToRef(Color color) {
+  // Windows device context does not support alpha.
+  return RGB(color.red(), color.green(), color.blue());
+}
+
 // A ScreenDrawer implementation for Windows.
 class ScreenDrawerWin : public ScreenDrawer {
  public:
@@ -42,10 +48,17 @@ class ScreenDrawerWin : public ScreenDrawer {
 
   // ScreenDrawer interface.
   DesktopRect DrawableRegion() override;
-  void DrawRectangle(DesktopRect rect, uint32_t rgba) override;
+  void DrawRectangle(DesktopRect rect, Color color) override;
   void Clear() override;
+  void WaitForPendingPaintings() override;
 
  private:
+  // Draw a line with |color|.
+  void DrawLine(DesktopVector start, DesktopVector end, Color color);
+
+  // Draw a dot with |color|.
+  void DrawDot(DesktopVector vect, Color color);
+
   const DesktopRect rect_;
   HWND window_;
   HDC hdc_;
@@ -57,8 +70,12 @@ ScreenDrawerWin::ScreenDrawerWin()
       window_(CreateDrawerWindow(rect_)),
       hdc_(GetWindowDC(window_)) {
   // We do not need to handle any messages for the |window_|, so disable Windows
-  // process windows ghosting feature.
+  // from processing windows ghosting feature.
   DisableProcessWindowsGhosting();
+
+  // Always use stock pen (DC_PEN) and brush (DC_BRUSH).
+  SelectObject(hdc_, GetStockObject(DC_PEN));
+  SelectObject(hdc_, GetStockObject(DC_BRUSH));
 }
 
 ScreenDrawerWin::~ScreenDrawerWin() {
@@ -71,20 +88,53 @@ 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));
+void ScreenDrawerWin::DrawRectangle(DesktopRect rect, Color color) {
+  if (rect.width() == 1 && rect.height() == 1) {
+    // Rectangle function cannot draw a 1 pixel rectangle.

[Jamie, 2016/08/26 22:29:10]

These special cases don't look right. The documentation for Rectangle states:

  The rectangle that is drawn excludes the bottom and right edges.

In other words, if a single-pixel rectangle doesn't work, it suggests that an
arbitrary rectangle will be 1px smaller that you asked for in each direction.
Maybe you just need to add 1 to both dimensions?

[Hzj_jie, 2016/08/29 21:57:28]

The ScreenDrawer::DrawRectangle has exactly the same behavior, i.e drawing a
rectangle from (a, b) to (c, d) will cover only (a, b) to (c - 1, d - 1).
(Excludes the bottom and right edges.) So if c == a + 1, i.e. 1 pixel width,
it's only a line from (a, b) to (a, d - 1).

And since I am not using PS_NULL, (AFAICT, it's BLACK_PEN with a different
color.) the border is also painted by |color|.

I believe this is a limitation of Windows Rectangle function, i.e. 1px height or
width rectangle is not existing in Windows GDI world.

[Jamie, 2016/08/31 17:39:39]

Thanks for the clarification.

+    DrawDot(rect.top_left(), color);
+    return;
+  }
+
+  if (rect.width() == 1 || rect.height() == 1) {
+    // Rectangle function cannot draw a 1 pixel rectangle.
+    DrawLine(rect.top_left(), DesktopVector(rect.right(), rect.bottom()),
+             color);
+    return;
+  }
+
+  SetDCBrushColor(hdc_, ColorToRef(color));
+  SetDCPenColor(hdc_, ColorToRef(color));
   Rectangle(hdc_, rect.left(), rect.top(), rect.right(), rect.bottom());
 }
 
 void ScreenDrawerWin::Clear() {
-  DrawRectangle(DrawableRegion(), 0);
+  DesktopRect rect =
+      DesktopRect::MakeWH(DrawableRegion().width(), DrawableRegion().height());
+  DrawRectangle(rect, Color::FromBGR(0));
+}
+
+// TODO(zijiehe): Find the right signal to indicate the finish of all pending
+// paintings.
+void ScreenDrawerWin::WaitForPendingPaintings() {
+  // DirectX capturer reads data from GPU, so there is a certain delay before
+  // Windows sends the data to GPU.
+  SleepMs(100);
+}
+
+void ScreenDrawerWin::DrawLine(DesktopVector start,
+                               DesktopVector end,
+                               Color color) {
+  POINT points[2];
+  points[0].x = start.x();
+  points[0].y = start.y();
+  points[1].x = end.x();
+  points[1].y = end.y();
+  SetDCPenColor(hdc_, ColorToRef(color));
+  Polyline(hdc_, points, 2);
+}
+
+void ScreenDrawerWin::DrawDot(DesktopVector vect, Color color) {
+  SetPixel(hdc_, vect.x(), vect.y(), ColorToRef(color));
 }
 
 }  // namespace