Currently there is not way to programmically test whether a ScreenCapturer

implementation can accurately capture updated regions. Especially in
ScreenCapturerWinDirectx, which has a specific updated region spreading logic
and cannot be tested through regular code path. So we need a controllable
ScreenDrawer to draw some basic shapes on the screen. And a platform independent
test case can use the ScreenDrawer to test a ScreenCapturer.

So this change addes a ScreenDrawer virtual class, and its Windows
implementation ScreenDrawerWin. A disabled gtest ScreenDrawerTest.DrawRectangles
is also added to manually test whether ScreenDrawer can work on a certain
platform.

BUG=314516

TBR=kjellander@webrtc.org

Review-Url: https://codereview.webrtc.org/2210443002
Cr-Commit-Position: refs/heads/master@{#13788}

webrtc/modules/BUILD.gn

@@ -369,6 +369,11 @@ if (rtc_include_tests) {
         "desktop_capture/screen_capturer_mac_unittest.cc",
         "desktop_capture/screen_capturer_mock_objects.h",
         "desktop_capture/screen_capturer_unittest.cc",
+        "desktop_capture/screen_drawer.h",
+        "desktop_capture/screen_drawer_linux.cc",
+        "desktop_capture/screen_drawer_mac.cc",
+        "desktop_capture/screen_drawer_unittest.cc",
+        "desktop_capture/screen_drawer_win.cc",
         "desktop_capture/win/cursor_unittest.cc",
         "desktop_capture/win/cursor_unittest_resources.h",
         "desktop_capture/win/cursor_unittest_resources.rc",

webrtc/modules/desktop_capture/screen_drawer.h

@@ -0,0 +1,46 @@
+/*
+ *  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.
+ */
+
+#ifndef WEBRTC_MODULES_DESKTOP_CAPTURE_SCREEN_DRAWER_H_
+#define WEBRTC_MODULES_DESKTOP_CAPTURE_SCREEN_DRAWER_H_
+
+#include <stdint.h>
+
+#include <memory>
+
+#include "webrtc/modules/desktop_capture/desktop_geometry.h"
+
+namespace webrtc {
+
+// A set of platform independent functions to draw various of shapes on the
+// screen. This class is for testing ScreenCapturer* implementations only, and
+// should not be used in production logic.
+class ScreenDrawer {
+ public:
+  // Creates a ScreenDrawer for the current platform.
+  static std::unique_ptr<ScreenDrawer> Create();
+
+  ScreenDrawer() {}
+  virtual ~ScreenDrawer() {}
+
+  // Returns a rect, on which this instance can draw.
+  virtual DesktopRect DrawableRegion() = 0;
+
+  // Draws a rectangle to cover |rect| with color |rgba|. Note, rect.bottom()
+  // and rect.right() two lines are not included.
+  virtual void DrawRectangle(DesktopRect rect, uint32_t rgba) = 0;
+
+  // Clears all content on the screen.
+  virtual void Clear() = 0;
+};
+
+}  // namespace webrtc
+
+#endif  // WEBRTC_MODULES_DESKTOP_CAPTURE_SCREEN_DRAWER_H_

webrtc/modules/desktop_capture/screen_drawer_linux.cc

@@ -0,0 +1,106 @@
+/*
+ *  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

webrtc/modules/desktop_capture/screen_drawer_mac.cc

@@ -0,0 +1,22 @@
+/*
+ *  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.
+ */
+
+// TODO(zijiehe): Implement ScreenDrawerMac
+
+#include "webrtc/modules/desktop_capture/screen_drawer.h"
+
+namespace webrtc {
+
+// static
+std::unique_ptr<ScreenDrawer> ScreenDrawer::Create() {
+  return nullptr;
+}
+
+}  // namespace webrtc

webrtc/modules/desktop_capture/screen_drawer_unittest.cc

@@ -0,0 +1,55 @@
+/*
+ *  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 "webrtc/modules/desktop_capture/screen_drawer.h"
+
+#include <stdint.h>
+
+#include "testing/gtest/include/gtest/gtest.h"
+#include "webrtc/base/random.h"
+#include "webrtc/base/timeutils.h"
+#include "webrtc/system_wrappers/include/sleep.h"
+
+namespace webrtc {
+
+// These are a set of manual test cases, as we do not have an automatical way to
+// detect whether a ScreenDrawer on a certain platform works well without
+// ScreenCapturer(s). So you may execute these test cases with
+// --gtest_also_run_disabled_tests --gtest_filter=ScreenDrawerTest.*.
+TEST(ScreenDrawerTest, DISABLED_DrawRectangles) {
+  std::unique_ptr<ScreenDrawer> drawer = ScreenDrawer::Create();
+  if (!drawer) {
+    // No ScreenDrawer implementation for current platform.
+    return;
+  }
+
+  drawer->Clear();
+  DesktopRect rect = drawer->DrawableRegion();
+  Random random(rtc::TimeMicros());
+  for (int i = 0; i < 100; i++) {
+    // Make sure we at least draw one pixel.
+    int left = random.Rand(rect.left(), rect.right() - 2);
+    int top = random.Rand(rect.top(), rect.bottom() - 2);
+    drawer->DrawRectangle(
+        DesktopRect::MakeLTRB(left, top, random.Rand(left + 1, rect.right()),
+                              random.Rand(top + 1, rect.bottom())),
+        random.Rand<uint32_t>());
+
+    if (i == 50) {
+      SleepMs(10000);
+      drawer->Clear();
+    }
+  }
+
+  SleepMs(10000);
+  drawer->Clear();
+}
+
+}  // namespace webrtc

webrtc/modules/desktop_capture/screen_drawer_win.cc

@@ -0,0 +1,97 @@
+/*
+ *  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

webrtc/modules/modules.gyp

@@ -428,6 +428,11 @@
                 'desktop_capture/screen_capturer_mac_unittest.cc',
                 'desktop_capture/screen_capturer_mock_objects.h',
                 'desktop_capture/screen_capturer_unittest.cc',
+                'desktop_capture/screen_drawer.h',
+                'desktop_capture/screen_drawer_linux.cc',
+                'desktop_capture/screen_drawer_mac.cc',
+                'desktop_capture/screen_drawer_unittest.cc',
+                'desktop_capture/screen_drawer_win.cc',
                 'desktop_capture/window_capturer_unittest.cc',
                 'desktop_capture/win/cursor_unittest.cc',
                 'desktop_capture/win/cursor_unittest_resources.h',