Add DesktopShapeTracker with implementation for Windows

remoting/host/desktop_shape_tracker_win.cc

+// Copyright (c) 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "remoting/host/desktop_shape_tracker.h"
+
+#include <vector>
+
+#include "base/memory/scoped_ptr.h"
+#include "base/win/scoped_gdi_object.h"
+#include "third_party/webrtc/modules/desktop_capture/desktop_capture_options.h"
+#include "third_party/webrtc/modules/desktop_capture/desktop_region.h"
+
+namespace remoting {
+
+namespace {
+
+struct EnumDesktopShapeData {
+  EnumDesktopShapeData()
+    : window_region(CreateRectRgn(0, 0, 0, 0)),
+      desktop_region(CreateRectRgn(0, 0, 0, 0)) {
+  }
+  base::win::ScopedRegion window_region;
+  base::win::ScopedRegion desktop_region;
+};
+
+class DesktopShapeTrackerWin : public DesktopShapeTracker {
+ public:
+  DesktopShapeTrackerWin();
+  virtual ~DesktopShapeTrackerWin();
+
+  virtual void RefreshDesktopShape();
+  virtual const webrtc::DesktopRegion& desktop_shape();
+
+ private:
+  // Callback passed to EnumWindows() to enumerate windows.
+  static BOOL CALLBACK EnumWindowsCallback(HWND window, LPARAM lparam);
+
+  // The most recently calculated desktop region.
+  webrtc::DesktopRegion desktop_shape_;
+
+  // Stored to compare with newly calculated desktop shapes, to avoid converting
+  // to an DesktopRegion unless the shape has actually changed.
+  base::win::ScopedRegion old_desktop_region_;
+
+  DISALLOW_COPY_AND_ASSIGN(DesktopShapeTrackerWin);
+};
+
+DesktopShapeTrackerWin::DesktopShapeTrackerWin()
+  : old_desktop_region_(CreateRectRgn(0, 0, 0, 0)) {
+}
+
+DesktopShapeTrackerWin::~DesktopShapeTrackerWin() {
+}
+
+void DesktopShapeTrackerWin::RefreshDesktopShape() {
+  // Accumulate a new desktop shape from current window positions.
+  scoped_ptr<EnumDesktopShapeData> shape_data(new EnumDesktopShapeData);
+  if (!EnumWindows(EnumWindowsCallback, (LPARAM)shape_data.get())) {
+    LOG_GETLASTERROR(ERROR) << "Failed to enumerate windows";
+    desktop_shape_.Clear();
+    return;
+  }
+
+  // If the shape has changed, refresh |desktop_shape_|.
+  if (!EqualRgn(shape_data->desktop_region, old_desktop_region_)) {
+    old_desktop_region_.Set(shape_data->desktop_region.release());
+
+    // Determine the size of output buffer required to receive the region.
+    DWORD bytes_size = GetRegionData(old_desktop_region_, 0, NULL);
+    CHECK(bytes_size != 0);
+
+    // Fetch the Windows RECTs that comprise the region.
+    std::vector<char> buffer(bytes_size);;
+    LPRGNDATA region_data = reinterpret_cast<LPRGNDATA>(buffer.data());
+    DWORD result = GetRegionData(old_desktop_region_, bytes_size, region_data);
+    CHECK(result == bytes_size);
+    const LPRECT rects = reinterpret_cast<LPRECT>(&region_data->Buffer[0]);
+
+    // Reset |desktop_shape_| and add new rectangles into it.
+    desktop_shape_.Clear();
+    for (size_t i = 0; i < region_data->rdh.nCount; ++i) {
+      desktop_shape_.AddRect(webrtc::DesktopRect::MakeLTRB(
+          rects[i].left, rects[i].top, rects[i].right, rects[i].bottom));
+    }
+  }
+}
+
+const webrtc::DesktopRegion& DesktopShapeTrackerWin::desktop_shape() {
+  return desktop_shape_;
+}
+
+// static
+BOOL DesktopShapeTrackerWin::EnumWindowsCallback(HWND window, LPARAM lparam) {
+  EnumDesktopShapeData* data = reinterpret_cast<EnumDesktopShapeData*>(lparam);
+  HRGN desktop_region = data->desktop_region.Get();
+  HRGN window_region = data->window_region.Get();
+
+  // Is the window visible?
+  if (!IsWindow(window) || !IsWindowVisible(window) || IsIconic(window))
+    return TRUE;
+
+  // Find the desktop position of the window (including non-client-area).
+  RECT window_rect;
+  if (!GetWindowRect(window, &window_rect))
+    return TRUE;
+
+  // Find the shape of the window, in window coords.
+  // GetWindowRgn will overwrite the current contents of |window_region|.
+  if (GetWindowRgn(window, window_region) != ERROR) {
+    // Translate the window region into desktop coordinates.
+    OffsetRgn(window_region, window_rect.left, window_rect.top);
+  } else {
+    // Window has no shape, or an error occurred, so assume it's rectangular.
+    SetRectRgn(window_region, window_rect.left, window_rect.top,
+               window_rect.right, window_rect.bottom);
+  }
+
+  // TODO(wez): If the window is maximized then we should clip it to the
+  // display on which it is maximized.
+  //  if (IsZoomed(window))
+  //    CombineRgn(window_region, window_region, screen_region, RGN_AND);
+
+  // Merge the window region into the accumulated desktop region.  Window
+  // regions are combined together before converting the result to
+  // DesktopRegion. It assumed that this approach is more efficient than
+  // converting each window region individually.
+  CombineRgn(desktop_region, desktop_region, window_region, RGN_OR);
+
+  return TRUE;
+}
+
+} // namespace
+
+// static
+scoped_ptr<DesktopShapeTracker> DesktopShapeTracker::Create(
+    webrtc::DesktopCaptureOptions options) {
+  return scoped_ptr<DesktopShapeTracker>(new DesktopShapeTrackerWin());
+}
+
+}  // namespace remoting