Support remoting of all monitors on multi-monitor Windows systems

remoting/host/capturer_win.cc

Index: remoting/host/capturer_win.cc
diff --git a/remoting/host/capturer_win.cc b/remoting/host/capturer_win.cc
index cae0326b29e0bc96f18324f838439bf43f29df2a..3a7fe50fdfbcccd3f78ef75012e8a9e87b25ac11 100644
--- a/remoting/host/capturer_win.cc
+++ b/remoting/host/capturer_win.cc
@@ -88,7 +88,9 @@ class CapturerGdi : public Capturer {
   void CaptureRegion(const SkRegion& region,
                      const CaptureCompletedCallback& callback);
 
-  void ReleaseBuffers();
+  // Release all GDI resources, including bitmaps and device contexts.
+  void ReleaseGdiResources();
+
   // Generates an image in the current buffer.
   void CaptureImage();
 
@@ -121,8 +123,7 @@ class CapturerGdi : public Capturer {
 
   ScopedThreadDesktopWin desktop_;
 
-  // Gdi specific information about screen.
-  HWND desktop_window_;
+  // GDI resources used for screen capture.
   HDC desktop_dc_;

[alexeypa (please no reviews), 2012/07/02 15:50:11]

nit: There are ScopedGetDC and ScopedCreateDC available.

[Wez, 2012/07/03 20:56:26]

Done.

   HDC memory_dc_;
   HBITMAP target_bitmap_[kNumBuffers];

[alexeypa (please no reviews), 2012/07/02 15:50:11]

nit: ScopedBitmap can be used here.

[Wez, 2012/07/03 20:56:26]

Done.

@@ -153,7 +154,6 @@ static const int kBytesPerPixel = 4;
 
 CapturerGdi::CapturerGdi()
     : last_cursor_size_(SkISize::Make(0, 0)),
-      desktop_window_(NULL),
       desktop_dc_(NULL),
       memory_dc_(NULL),
       dc_size_(SkISize::Make(0, 0)),
@@ -166,7 +166,7 @@ CapturerGdi::CapturerGdi()
 }
 
 CapturerGdi::~CapturerGdi() {
-  ReleaseBuffers();
+  ReleaseGdiResources();
 }
 
 media::VideoFrame::Format CapturerGdi::pixel_format() const {
@@ -208,7 +208,7 @@ const SkISize& CapturerGdi::size_most_recent() const {
   return helper_.size_most_recent();
 }
 
-void CapturerGdi::ReleaseBuffers() {
+void CapturerGdi::ReleaseGdiResources() {
   for (int i = kNumBuffers - 1; i >= 0; i--) {
     if (target_bitmap_[i]) {
       DeleteObject(target_bitmap_[i]);
@@ -221,8 +221,7 @@ void CapturerGdi::ReleaseBuffers() {
   }
 
   if (desktop_dc_) {
-    ReleaseDC(desktop_window_, desktop_dc_);
-    desktop_window_ = NULL;
+    ReleaseDC(NULL, desktop_dc_);
     desktop_dc_ = NULL;
   }
 
@@ -272,46 +271,25 @@ void CapturerGdi::UpdateBufferCapture(const SkISize& size) {
   scoped_ptr<DesktopWin> input_desktop = DesktopWin::GetInputDesktop();
   if (input_desktop.get() != NULL && !desktop_.IsSame(*input_desktop)) {
     // Release GDI resources otherwise SetThreadDesktop will fail.
-    if (desktop_dc_) {
-      ReleaseDC(desktop_window_, desktop_dc_);
-      desktop_window_ = NULL;
-      desktop_dc_ = NULL;
-    }
-
-    if (memory_dc_) {
-      DeleteDC(memory_dc_);
-      memory_dc_ = NULL;
-    }
-
-    ReleaseBuffers();
+    ReleaseGdiResources();
 
     // If SetThreadDesktop() fails, the thread is still assigned a desktop.
     // So we can continue capture screen bits, just from a diffented desktop.
     desktop_.SetThreadDesktop(input_desktop.Pass());
   }
 
-  // Make sure the DCs have the correct dimensions.
+  // If the display dimensions have changed then recreate GDI resources.
   if (size != dc_size_) {
-    // TODO(simonmorris): screen dimensions changing isn't equivalent to needing
-    // a new DC, but it's good enough for now.
-    if (desktop_dc_) {
-      ReleaseDC(desktop_window_, desktop_dc_);
-      desktop_window_ = NULL;
-      desktop_dc_ = NULL;
-    }
-
-    if (memory_dc_) {
-      DeleteDC(memory_dc_);
-      memory_dc_ = NULL;
-    }
+    ReleaseGdiResources();
   }
 
+  // Create GDI device contexts to capture from the desktop into memory.
   if (desktop_dc_ == NULL) {
-    DCHECK(desktop_window_ == NULL);
     DCHECK(memory_dc_ == NULL);
+    DCHECK(target_bitmap_[0] == NULL);
+    DCHECK(buffers_[0].data == NULL);
 
-    desktop_window_ = GetDesktopWindow();
-    desktop_dc_ = GetDC(desktop_window_);
+    desktop_dc_ = GetDC(NULL);
     memory_dc_ = CreateCompatibleDC(desktop_dc_);
     dc_size_ = size;
   }
@@ -431,7 +409,8 @@ void CapturerGdi::CaptureImage() {
 
   // And then copy the rect from desktop to memory.
   BitBlt(memory_dc_, 0, 0, buffers_[current_buffer_].size.width(),
-      buffers_[current_buffer_].size.height(), desktop_dc_, 0, 0,
+      buffers_[current_buffer_].size.height(), desktop_dc_,
+      GetSystemMetrics(SM_XVIRTUALSCREEN), GetSystemMetrics(SM_YVIRTUALSCREEN),

[alexeypa (please no reviews), 2012/07/02 15:50:11]

There is a race between this code and CapturerGdi::GetScreeenSize(). The screen
dimension should be grabbed only once when the buffers are allocated. 

[Wez, 2012/07/03 20:56:26]

There's no race as such, since the width & height and top/left coordinates can
vary independently of one another. There is a race between this and the DC being
re-allocated, since the DC's origin is what we're actually interested in here,
but that will at worst result in a temporary rendering glitch during
reconfiguration events; it's not avoidable since the displays can be
reconfigured asynchronously to any processing we do here - they could even
change in-between GetSystemMetrics() calls.

I've changed this code to test the coordinates of the desktop, not just the
dimensions, and to fetch the coordinates of the desktop in one place.

       SRCCOPY | CAPTUREBLT);
 }
 
@@ -609,8 +588,8 @@ void CapturerGdi::CaptureCursor() {
 }
 
 SkISize CapturerGdi::GetScreenSize() {
-  return SkISize::Make(GetSystemMetrics(SM_CXSCREEN),
-                       GetSystemMetrics(SM_CYSCREEN));
+  return SkISize::Make(GetSystemMetrics(SM_CXVIRTUALSCREEN),
+                       GetSystemMetrics(SM_CYVIRTUALSCREEN));
 }
 
 }  // namespace