Support Drag and Drop across displays.

ash/drag_drop/drag_drop_controller.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_controller.h"
 
+#include "ash/drag_drop/drag_drop_tracker.h"
 #include "ash/drag_drop/drag_image_view.h"
 #include "ash/shell.h"
 #include "ash/wm/cursor_manager.h"
 #include "base/message_loop.h"
 #include "base/run_loop.h"
 #include "ui/aura/client/capture_client.h"
 #include "ui/aura/client/drag_drop_delegate.h"
 #include "ui/aura/env.h"
 #include "ui/aura/root_window.h"
 #include "ui/aura/window.h"
@@ skipping 20 matching lines @@
 
 ////////////////////////////////////////////////////////////////////////////////
 // DragDropController, public:
 
 DragDropController::DragDropController()
     : drag_image_(NULL),
       drag_data_(NULL),
       drag_operation_(0),
       drag_window_(NULL),
       drag_drop_in_progress_(false),
-      should_block_during_drag_drop_(true) {
+      should_block_during_drag_drop_(true),
+      drag_drop_tracker_(new DragDropTracker) {
   Shell::GetInstance()->AddEnvEventFilter(this);
 }
 
 DragDropController::~DragDropController() {
   Shell::GetInstance()->RemoveEnvEventFilter(this);
   Cleanup();
   if (drag_image_.get())
     drag_image_.reset();
 }
 
 int DragDropController::StartDragAndDrop(const ui::OSExchangeData& data,
+                                         aura::RootWindow* root_window,
                                          const gfx::Point& root_location,
                                          int operation) {
   DCHECK(!drag_drop_in_progress_);
-  // TODO(oshima): Add CaptureClient client API.
-  aura::Window* capture_window =
-      aura::client::GetCaptureWindow(Shell::GetPrimaryRootWindow());
-  if (capture_window)
-    capture_window->ReleaseCapture();
+
   drag_drop_in_progress_ = true;
   drag_cursor_ = ui::kCursorPointer;
+  drag_drop_tracker_->StartTracking(root_window);
 
   drag_data_ = &data;
   drag_operation_ = operation;
   const ui::OSExchangeDataProviderAura& provider =
       static_cast<const ui::OSExchangeDataProviderAura&>(data.provider());
 
   drag_image_.reset(new DragImageView);
   drag_image_->SetImage(provider.drag_image());
   drag_image_offset_ = provider.drag_image_offset();
   drag_image_->SetBoundsInScreen(gfx::Rect(
@@ skipping 127 matching lines @@
     DragCancel();
     return true;
   }
   return false;
 }
 
 bool DragDropController::PreHandleMouseEvent(aura::Window* target,
                                              ui::MouseEvent* event) {
   if (!drag_drop_in_progress_)
     return false;
-  switch (event->type()) {
+  aura::Window* translated_target = drag_drop_tracker_->GetTarget(*event);
+  if (!translated_target)
+    return false;

[varunjain, 2012/08/20 16:21:22]

when can this happen? Drag drop is in progress, so what happens if you let this
drag event fall through? My concern here is the user seeing some windows, where
the drag image and cursor are not updated.

[mazda, 2012/08/21 02:10:59]

This happens when the cursor goes out of root window when testing on desktop.
I don't think it happens on the real machine because the cursor cannot go out of
desktop background view.
Is it better to call Cleanup?

[varunjain, 2012/08/21 04:37:25]

How about calling DragCancel() instead. It will do the necessary cleanup and
also give the user a visual cue that the drag session is over.

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

Done.

+  scoped_ptr<ui::MouseEvent> translated_event(
+      drag_drop_tracker_->ConvertMouseEvent(translated_target, *event));
+  switch (translated_event->type()) {
     case ui::ET_MOUSE_DRAGGED:
-      DragUpdate(target, *event);
+      DragUpdate(translated_target, *translated_event.get());

[varunjain, 2012/08/20 16:21:22]

would you also require re-parenting the drag_image_ so the image shows up in the
right root window?

[mazda, 2012/08/21 02:10:59]

DragImageView::SetScreenPosition does it internally.
There was a bug that shows drag image always on the primary display
(http://crbug.com/141192), but it was fixed in another CL
(http://crrev.com/152339).

[varunjain, 2012/08/21 04:37:25]

cool! thanks for fixing!

       break;
     case ui::ET_MOUSE_RELEASED:
-      Drop(target, *event);
+      Drop(translated_target, *translated_event.get());
       break;
     default:
-      // We could reach here if the user drops outside the root window.
       // We could also reach here because RootWindow may sometimes generate a
       // bunch of fake mouse events
       // (aura::RootWindow::PostMouseMoveEventAfterWindowChange).
       break;
   }
   return true;
 }
 
 ui::TouchStatus DragDropController::PreHandleTouchEvent(

[sky, 2012/08/20 15:35:18]

Do you need to update touch similarly?

[varunjain, 2012/08/20 15:53:20]

Touch dnd does not currently work. I have a bug for it for m24. I can take care
of this then.

[mazda, 2012/08/21 02:10:59]

Could you tell me the issue ID? I'll add TODO comment.

[varunjain, 2012/08/21 04:37:25]

crbug.com/114755

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

Thanks. I added a TODO comment.

     aura::Window* target,
     ui::TouchEvent* event) {
   // TODO(sad): Also check for the touch-id.
   if (!drag_drop_in_progress_)
     return ui::TOUCH_STATUS_UNKNOWN;
   switch (event->type()) {
     case ui::ET_TOUCH_MOVED:
       DragUpdate(target, *event);
       break;
     case ui::ET_TOUCH_RELEASED:
@@ skipping 47 matching lines @@
   animation_setter.AddObserver(this);
   window->SetBounds(gfx::Rect(drag_start_location_, window->bounds().size()));
 }
 
 void DragDropController::Cleanup() {
   if (drag_window_)
     drag_window_->RemoveObserver(this);
   drag_window_ = NULL;
   drag_data_ = NULL;
   drag_drop_in_progress_ = false;
+  drag_drop_tracker_->StopTracking();
 }
 
 }  // namespace internal
 }  // namespace ash