First shot at implementing drag&drop for Aura

ui/aura_shell/desktop_event_filter.cc

Index: ui/aura_shell/desktop_event_filter.cc
diff --git a/ui/aura_shell/desktop_event_filter.cc b/ui/aura_shell/desktop_event_filter.cc
index d69ead118f5b8531c642c99d7b192ad33f9c0c13..a9ab7e36ade8ccdf9451637cf68ed2685f11a296 100644
--- a/ui/aura_shell/desktop_event_filter.cc
+++ b/ui/aura_shell/desktop_event_filter.cc
@@ -4,6 +4,8 @@
 
 #include "ui/aura_shell/desktop_event_filter.h"
 
+#include "ui/aura/client/aura_constants.h"
+#include "ui/aura/client/drag_drop_client.h"
 #include "ui/aura/desktop.h"
 #include "ui/aura/event.h"
 #include "ui/aura/focus_manager.h"
@@ -15,6 +17,30 @@
 namespace aura_shell {
 namespace internal {
 
+bool HandleDragDrop(aura::Window* target, aura::MouseEvent* event) {
+  aura::DragDropClient* drag_drop_client = static_cast<aura::DragDropClient*>(
+      aura::Desktop::GetInstance()->GetProperty(
+          aura::kDesktopDragDropClientKey));
+  if (drag_drop_client && drag_drop_client->IsDragAndDropInProgress()) {
+    switch (event->type()) {
+      case ui::ET_MOUSE_DRAGGED:
+        drag_drop_client->DragUpdate(target, *event);
+        break;
+      case ui::ET_MOUSE_RELEASED:
+        drag_drop_client->Drop(target, *event);
+        break;
+      case ui::ET_MOUSE_EXITED:
+        drag_drop_client->DragCancel();
+        break;
+      default:
+        NOTREACHED();
+        break;
+    }
+    return true;
+  }
+  return false;
+}
+
 // Returns the default cursor for a window component.
 gfx::NativeCursor CursorForWindowComponent(int window_component) {
   switch (window_component) {
@@ -70,6 +96,11 @@ bool DesktopEventFilter::PreHandleKeyEvent(aura::Window* target,
 
 bool DesktopEventFilter::PreHandleMouseEvent(aura::Window* target,
                                              aura::MouseEvent* event) {
+
+  // Give all events to the drag/drop controller is a drag/drop is in progress.
+  if (HandleDragDrop(target, event))

[Ben Goodger (Google), 2011/11/16 00:13:20]

Now that we support addtl event filters... just move this code to a separate
event filter and call AddFilter on this guy.

Then you'll be automagically called by FilterMouseEvent below!

[varunjain, 2011/11/16 20:30:15]

Done.

+    return true;
+
   if (FilterMouseEvent(target, event))
     return true;