Deflaky ScreenCapturerTest

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 08d8195b42dd66601351d02d138e081137e8220d..1d5d993144536420d8dd84bbc5b31a97734dfdc2 100644
--- a/webrtc/modules/desktop_capture/screen_drawer_linux.cc
+++ b/webrtc/modules/desktop_capture/screen_drawer_linux.cc
@@ -8,6 +8,10 @@
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
+#include <fcntl.h>
+#include <sys/stat.h>
+#include <semaphore.h>
+
 #include <memory>
 
 #include "webrtc/base/checks.h"
@@ -19,6 +23,35 @@ namespace webrtc {
 
 namespace {
 
+static constexpr char kSemaphoreName[] =
+    "/global-screen-drawer-linux-54fe5552-8047-11e6-a725-3f429a5b4fb4";
+
+// A cross application lock to ensure only one ScreenDrawerLinux can be used at
+// a certain time.
+struct ScreenDrawerLock {
+  // Blocks current thread until a global lock is acquired.
+  ScreenDrawerLock();
+  // Releases the global lock acquired.
+  ~ScreenDrawerLock();
+
+ private:
+  sem_t* semaphore_;
+};
+
+ScreenDrawerLock::ScreenDrawerLock() {
+  semaphore_ =
+      sem_open(kSemaphoreName, O_CREAT, S_IRWXU | S_IRWXG | S_IRWXO, 1);
+  sem_wait(semaphore_);
+}
+
+ScreenDrawerLock::~ScreenDrawerLock() {
+  sem_post(semaphore_);
+  sem_close(semaphore_);
+  // sem_unlink(kSemaphoreName);
+}
+
+std::unique_ptr<ScreenDrawerLock> g_screen_drawer_lock;
+
 // A ScreenDrawer implementation for X11.
 class ScreenDrawerLinux : public ScreenDrawer {
  public:
@@ -30,8 +63,13 @@ class ScreenDrawerLinux : public ScreenDrawer {
   void DrawRectangle(DesktopRect rect, RgbaColor color) override;
   void Clear() override;
   void WaitForPendingDraws() override;
+  bool MayDrawIncompleteShapes() override;
 
  private:
+  // Bring the window to the front, this can help to avoid the impact from other
+  // windows or shadow effect.
+  void BringToFront();
+
   rtc::scoped_refptr<SharedXDisplay> display_;
   int screen_num_;
   DesktopRect rect_;
@@ -80,6 +118,7 @@ ScreenDrawerLinux::ScreenDrawerLinux() {
                                 root_attributes.height);
   context_ = DefaultGC(display_->display(), screen_num_);
   colormap_ = DefaultColormap(display_->display(), screen_num_);
+  BringToFront();
   // Wait for window animations.
   SleepMs(200);
 }
@@ -87,6 +126,7 @@ ScreenDrawerLinux::ScreenDrawerLinux() {
 ScreenDrawerLinux::~ScreenDrawerLinux() {
   XUnmapWindow(display_->display(), window_);
   XDestroyWindow(display_->display(), window_);
+  g_screen_drawer_lock.reset();
 }
 
 DesktopRect ScreenDrawerLinux::DrawableRegion() {
@@ -118,14 +158,24 @@ void ScreenDrawerLinux::Clear() {
 // TODO(zijiehe): Find the right signal from X11 to indicate the finish of all
 // pending paintings.
 void ScreenDrawerLinux::WaitForPendingDraws() {
+  BringToFront();
   SleepMs(50);
 }
 
+bool ScreenDrawerLinux::MayDrawIncompleteShapes() {
+  return true;
+}
+
+void ScreenDrawerLinux::BringToFront() {
+  XRaiseWindow(display_->display(), window_);
+}
+
 }  // namespace
 
 // static
 std::unique_ptr<ScreenDrawer> ScreenDrawer::Create() {
   if (SharedXDisplay::CreateDefault().get()) {
+    g_screen_drawer_lock.reset(new ScreenDrawerLock());
     return std::unique_ptr<ScreenDrawer>(new ScreenDrawerLinux());
   }
   return nullptr;