Support Drag and Drop across displays.

ash/drag_drop/drag_drop_controller.cc

Index: ash/drag_drop/drag_drop_controller.cc
diff --git a/ash/drag_drop/drag_drop_controller.cc b/ash/drag_drop/drag_drop_controller.cc
index 445468a0fe287df2300f99bee6e7292194cccb90..cece6032bd64da52443c602b7845e1b3a9874b77 100644
--- a/ash/drag_drop/drag_drop_controller.cc
+++ b/ash/drag_drop/drag_drop_controller.cc
@@ -4,6 +4,7 @@
 
 #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"
@@ -44,7 +45,8 @@ DragDropController::DragDropController()
       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);
 }
 
@@ -56,16 +58,14 @@ DragDropController::~DragDropController() {
 }
 
 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;
@@ -213,15 +213,19 @@ 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).
@@ -298,6 +302,7 @@ void DragDropController::Cleanup() {
   drag_window_ = NULL;
   drag_data_ = NULL;
   drag_drop_in_progress_ = false;
+  drag_drop_tracker_->StopTracking();
 }
 
 }  // namespace internal