Several minor changes to ScreenCapturerWinMagnifier

webrtc/modules/desktop_capture/win/screen_capturer_win_magnifier.cc

Index: webrtc/modules/desktop_capture/win/screen_capturer_win_magnifier.cc
diff --git a/webrtc/modules/desktop_capture/win/screen_capturer_win_magnifier.cc b/webrtc/modules/desktop_capture/win/screen_capturer_win_magnifier.cc
index 7fdc8eb43fcbde80e735ae1bce3b03fb0fd0dae9..1c41b5f8a7011e41b3176d0cee061310e0e96d80 100644
--- a/webrtc/modules/desktop_capture/win/screen_capturer_win_magnifier.cc
+++ b/webrtc/modules/desktop_capture/win/screen_capturer_win_magnifier.cc
@@ -10,10 +10,9 @@
 
 #include "webrtc/modules/desktop_capture/win/screen_capturer_win_magnifier.h"
 
-#include <assert.h>
-
 #include <utility>
 
+#include "webrtc/base/checks.h"
 #include "webrtc/base/timeutils.h"
 #include "webrtc/modules/desktop_capture/desktop_capture_options.h"
 #include "webrtc/modules/desktop_capture/desktop_frame.h"
@@ -34,8 +33,7 @@ static LPCTSTR kMagnifierHostClass = L"ScreenCapturerWinMagnifierHost";
 static LPCTSTR kHostWindowName = L"MagnifierHost";
 static LPCTSTR kMagnifierWindowClass = L"Magnifier";
 static LPCTSTR kMagnifierWindowName = L"MagnifierWindow";
-
-Atomic32 ScreenCapturerWinMagnifier::tls_index_(TLS_OUT_OF_INDEXES);
+thread_local static ScreenCapturerWinMagnifier* kCurrent;

[Sergey Ulanov, 2016/09/19 20:53:18]

- thread_local is not listed on chromium-cpp.appspot.com, so I don't think it's
approved. 
- This is clearly not a const, so it shouldn't use const name.
- You probably need "= nullptr;" to make sure it gets initialized properly.

[Hzj_jie, 2016/09/19 22:05:23]

Emmm, a Google internal mail thread shows thread_local will eventually be the
norm. But yes, since it's not actively allowed. I will use __declspec(thread)
instead, which is MSVC specific implementation, and widely used in Chromium.

Others are updated.

[Sergey Ulanov, 2016/09/19 22:21:25]

__declspec(thread) seems used in some third-party projects, but not in chromium
itself. It's also not used in WebRTC, so I'd prefer avoiding it as well. What's
the reason we cannot keep tls_index?

 
 ScreenCapturerWinMagnifier::ScreenCapturerWinMagnifier(
     std::unique_ptr<ScreenCapturer> fallback_capturer)
@@ -62,7 +60,9 @@ void ScreenCapturerWinMagnifier::Start(Callback* callback) {
   assert(callback);
   callback_ = callback;
 
-  InitializeMagnifier();
+  if (!InitializeMagnifier()) {
+    StartFallbackCapturer();
+  }
 }
 
 void ScreenCapturerWinMagnifier::SetSharedMemoryFactory(
@@ -75,14 +75,6 @@ void ScreenCapturerWinMagnifier::Capture(const DesktopRegion& region) {
 
   queue_.MoveToNextFrame();
 
-  // Request that the system not power-down the system, or the display hardware.
-  if (!SetThreadExecutionState(ES_DISPLAY_REQUIRED | ES_SYSTEM_REQUIRED)) {
-    if (!set_thread_execution_state_failed_) {
-      set_thread_execution_state_failed_ = true;
-      LOG_F(LS_WARNING) << "Failed to make system & display power assertion: "
-                        << GetLastError();
-    }
-  }
   // Switch to the desktop receiving user input if different from the current
   // one.
   std::unique_ptr<Desktop> input_desktop(Desktop::GetInputDesktop());
@@ -101,8 +93,7 @@ void ScreenCapturerWinMagnifier::Capture(const DesktopRegion& region) {
 
   // Do not try to use the magnifier if it failed before and in multi-screen
   // setup (where the API crashes sometimes).
-  if (magnifier_initialized_ && (GetSystemMetrics(SM_CMONITORS) == 1) &&
-      magnifier_capture_succeeded_) {
+  if (magnifier_initialized_ && magnifier_capture_succeeded_) {
     DesktopRect rect = GetScreenRect(current_screen_id_, current_device_key_);
     CreateCurrentFrameIfNecessary(rect.size());
 
@@ -120,6 +111,7 @@ void ScreenCapturerWinMagnifier::Capture(const DesktopRegion& region) {
 
   const DesktopFrame* current_frame = queue_.current_frame();
   const DesktopFrame* last_frame = queue_.previous_frame();
+  DesktopRegion updated_region;
   if (last_frame && last_frame->size().equals(current_frame->size())) {
     // Make sure the differencer is set up correctly for these previous and
     // current screens.
@@ -133,24 +125,17 @@ void ScreenCapturerWinMagnifier::Capture(const DesktopRegion& region) {
     }
 
     // Calculate difference between the two last captured frames.
-    DesktopRegion region;
     differ_->CalcDirtyRegion(

[Sergey Ulanov, 2016/09/19 20:53:18]

Do we need to keep the differ here?

[Hzj_jie, 2016/09/19 22:05:23]

No, but all the differs will be removed in
https://codereview.chromium.org/2348803003/.

-        last_frame->data(), current_frame->data(), &region);
-    helper_.InvalidateRegion(region);
+        last_frame->data(), current_frame->data(), &updated_region);
   } else {
-    // No previous frame is available, or the screen is resized. Invalidate the
-    // whole screen.
-    helper_.InvalidateScreen(current_frame->size());
+    updated_region.SetRect(DesktopRect::MakeSize(current_frame->size()));
   }
 
-  helper_.set_size_most_recent(current_frame->size());
-
   // Emit the current frame.
   std::unique_ptr<DesktopFrame> frame = queue_.current_frame()->Share();
   frame->set_dpi(DesktopVector(GetDeviceCaps(desktop_dc_, LOGPIXELSX),
                                GetDeviceCaps(desktop_dc_, LOGPIXELSY)));
-  frame->mutable_updated_region()->Clear();
-  helper_.TakeInvalidRegion(frame->mutable_updated_region());
+  frame->mutable_updated_region()->Swap(&updated_region);
   frame->set_capture_time_ms((rtc::TimeNanos() - capture_start_time_nanos) /
                              rtc::kNumNanosecsPerMillisec);
   callback_->OnCaptureResult(Result::SUCCESS, std::move(frame));
@@ -200,6 +185,7 @@ bool ScreenCapturerWinMagnifier::CaptureImage(const DesktopRect& rect) {
 
   RECT native_rect = {rect.left(), rect.top(), rect.right(), rect.bottom()};
 
+  kCurrent = this;
   // OnCaptured will be called via OnMagImageScalingCallback and fill in the
   // frame before set_window_source_func_ returns.
   result = set_window_source_func_(magnifier_window_, native_rect);
@@ -223,19 +209,18 @@ BOOL ScreenCapturerWinMagnifier::OnMagImageScalingCallback(
     RECT unclipped,
     RECT clipped,
     HRGN dirty) {
-  assert(tls_index_.Value() != static_cast<int32_t>(TLS_OUT_OF_INDEXES));
-
-  ScreenCapturerWinMagnifier* owner =
-      reinterpret_cast<ScreenCapturerWinMagnifier*>(
-          TlsGetValue(tls_index_.Value()));
-
-  owner->OnCaptured(srcdata, srcheader);
-
+  RTC_DCHECK(kCurrent != nullptr);

[Sergey Ulanov, 2016/09/19 20:53:18]

Please replace all asserts with RTC_DCHECK

[Hzj_jie, 2016/09/19 22:05:23]

Done.

+  kCurrent->OnCaptured(srcdata, srcheader);
   return TRUE;
 }
 
 bool ScreenCapturerWinMagnifier::InitializeMagnifier() {
   assert(!magnifier_initialized_);
+  if (GetSystemMetrics(SM_CMONITORS) != 1) {

[Sergey Ulanov, 2016/09/19 20:53:18]

I think it's better to keep this check in ScreenCapturerWinMagnifier::Capture().
Number of monitors can change dynamically while the capturer is active.

[Hzj_jie, 2016/09/19 22:05:23]

Good point. Updated.

+    // Do not try to use the magnifier if it failed before and in multi-screen
+    // setup (where the API crashes sometimes).
+    return false;
+  }
 
   desktop_dc_ = GetDC(nullptr);
 
@@ -345,17 +330,6 @@ bool ScreenCapturerWinMagnifier::InitializeMagnifier() {
     }
   }
 
-  if (tls_index_.Value() == static_cast<int32_t>(TLS_OUT_OF_INDEXES)) {
-    // More than one threads may get here at the same time, but only one will
-    // write to tls_index_ using CompareExchange.
-    DWORD new_tls_index = TlsAlloc();
-    if (!tls_index_.CompareExchange(new_tls_index, TLS_OUT_OF_INDEXES))
-      TlsFree(new_tls_index);
-  }
-
-  assert(tls_index_.Value() != static_cast<int32_t>(TLS_OUT_OF_INDEXES));
-  TlsSetValue(tls_index_.Value(), this);
-
   magnifier_initialized_ = true;
   return true;
 }