Support Drag and Drop across displays.

ash/drag_drop/drag_drop_tracker.cc

+// Copyright (c) 2012 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 "ash/drag_drop/drag_drop_tracker.h"
+
+#include "ash/shell.h"
+#include "ash/shell_window_ids.h"
+#include "ash/wm/coordinate_conversion.h"
+#include "ui/aura/root_window.h"
+#include "ui/base/event.h"
+#include "ui/gfx/screen.h"
+
+namespace {
+
+// Creates a window for capturing drag events.
+aura::Window* CreateCaptureWindow(aura::RootWindow* root_window) {
+  aura::Window* window = new aura::Window(NULL);
+  window->SetType(aura::client::WINDOW_TYPE_NORMAL);
+  window->Init(ui::LAYER_NOT_DRAWN);
+  window->SetParent(NULL);
+  window->SetBoundsInScreen(root_window->GetBoundsInScreen(),
+                            gfx::Screen::GetDisplayNearestWindow(root_window));
+  window->Show();
+  return window;
+}
+
+}  // namespace
+
+namespace ash {
+namespace internal {
+
+DragDropTracker::DragDropTracker(aura::RootWindow* root_window)
+    : capture_window_(CreateCaptureWindow(root_window)) {
+  capture_window_->SetCapture();

[varunjain, 2012/08/21 04:37:26]

Do you also need to listen to OnWindowDestroying on the capture_window_?

[mazda, 2012/08/24 08:29:01]

I don't think it's necessary to listen to OnWindowDestroying. 
When secondary display is disconnected, |capture_window_| is not deleted but
moved to primary root window, so I do not need it for this case.
The primary root window is deleted after DragDropController in Shell, so
OnWindowDestroying is not called for |capture_window_|.

+}
+
+DragDropTracker::~DragDropTracker()  {
+  capture_window_->ReleaseCapture();
+}
+
+aura::Window* DragDropTracker::GetTarget(const ui::LocatedEvent& event) {
+  std::pair<aura::RootWindow*, gfx::Point> pair =
+      ash::wm::GetRootWindowRelativeToWindow(capture_window_.get(),
+                                             event.location());
+  return pair.first->GetEventHandlerForPoint(pair.second);
+}
+
+ui::MouseEvent* DragDropTracker::ConvertMouseEvent(
+    aura::Window* target,
+    const ui::MouseEvent& event) {
+  DCHECK(capture_window_.get());
+  std::pair<aura::RootWindow*, gfx::Point> location_pair =
+      ash::wm::GetRootWindowRelativeToWindow(capture_window_.get(),
+                                             event.location());
+  aura::Window::ConvertPointToTarget(location_pair.first, target,
+                                     &location_pair.second);
+  std::pair<aura::RootWindow*, gfx::Point> root_location_pair =
+      ash::wm::GetRootWindowRelativeToWindow(capture_window_->GetRootWindow(),
+                                             event.root_location());
+  return new ui::MouseEvent(event.type(),
+                            location_pair.second,
+                            root_location_pair.second,
+                            event.flags());
+}
+
+}  // namespace internal
+}  // namespace ash