mus: Implement interwindow drag and drop

services/ui/ws/current_drag_operation.h

Index: services/ui/ws/current_drag_operation.h
diff --git a/services/ui/ws/current_drag_operation.h b/services/ui/ws/current_drag_operation.h
new file mode 100644
index 0000000000000000000000000000000000000000..c2263cd5eabe8eac54d0a21bcc6165cdb7fd1cb2
--- /dev/null
+++ b/services/ui/ws/current_drag_operation.h
@@ -0,0 +1,99 @@
+// Copyright 2016 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.
+
+#ifndef SERVICES_UI_WS_CURRENT_DRAG_OPERATION_H_
+#define SERVICES_UI_WS_CURRENT_DRAG_OPERATION_H_
+
+#include <deque>
+
+#include "base/memory/weak_ptr.h"
+#include "services/ui/common/types.h"
+#include "services/ui/ws/ids.h"
+#include "services/ui/ws/server_window_observer.h"
+
+namespace ui {
+namespace ws {
+
+namespace test {
+class CurrentDragOperationTestApi;
+}
+
+class CurrentDragOperationSource;
+
+// Represents all the data around the current ongoing drag operation.
+//
+// There should only be one instance of this class per userid. The
+// WindowManagerState's EventDispatcher creates and owns this instance.
+class CurrentDragOperation : public ServerWindowObserver {

[sky, 2016/09/06 21:11:27]

Is 'current' really helpful in this context? Is just DragOperation or
DragController better?

+ public:
+  CurrentDragOperation(CurrentDragOperationSource* source,
+                       ServerWindow* window,
+                       mojo::Map<mojo::String, mojo::Array<uint8_t>> mime_data,
+                       uint32_t drag_operations);
+  ~CurrentDragOperation() override;
+
+  // Cancels the current drag, ie, due to the user pressing Escape.
+  void DispatchCancel();

[sky, 2016/09/06 21:11:27]

I would just call this Cancel().

+
+  // Responds to a pointer move/release event.
+  void DispatchLocatedEvent(const ui::LocatedEvent& event,
+                            ServerWindow* current_target);
+
+ private:
+  friend class test::CurrentDragOperationTestApi;
+  enum DragEventType { TYPE_ENTER, TYPE_OVER, TYPE_LEAVE, TYPE_DROP };

[sky, 2016/09/06 21:11:27]

enum class, and nuke TYPE_?

+  struct Operation;
+
+  // Notifies all windows we messaged that the drag is finished, and then tell
+  // |source| the result.
+  void MessageDragCompleted(bool success);
+
+  size_t GetSizeOfQueueForWindow(ServerWindow* window);

[sky, 2016/09/06 21:11:27]

Description.

+
+  void QueueEvent(ServerWindow* window,
+                  DragEventType type,
+                  uint32_t key_state,
+                  gfx::Point position);
+  void RemoveQueueFront(ServerWindow* window);
+  void DispatchFrontOfWindowQueue(ServerWindow* window,
+                                  std::deque<Operation>* queue);
+
+  // Callback methods.
+  void OnDragStatusCompleted(const WindowId& id, uint32_t bitmask);
+  void OnDragDropCompleted(const WindowId& id, uint32_t bitmask);
+
+  // ServerWindowObserver:
+  void OnWindowDestroying(ServerWindow* window) override;
+
+  // Our owner.
+  CurrentDragOperationSource* source_ = nullptr;
+
+  uint32_t drag_operations_;

[sky, 2016/09/06 21:11:27]

const?

+
+  bool waiting_for_final_drop_response_ = false;
+
+  ServerWindow* source_window_ = nullptr;
+  ServerWindow* current_target_window_ = nullptr;
+
+  // A list of the offered mime types.
+  mojo::Map<mojo::String, mojo::Array<uint8_t>> mime_data_;
+
+  // Event queues for each window. If a vector is empty, there are no
+  // operations going on. If a vector has one operation, we're waiting on a
+  // response for that operation from the client. Every operation past the
+  // first is queued.
+  std::map<ServerWindow*, std::deque<Operation>> current_window_state_;

[sky, 2016/09/06 21:11:27]

window_operations_?

+
+  // A set of ServerWindows* which have received the PerformOnDragStart() call.
+  std::set<ServerWindow*> called_on_drag_start_;
+
+  base::WeakPtrFactory<CurrentDragOperation> weak_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(CurrentDragOperation);
+};
+
+}  // namespace ws
+}  // namespace ui
+
+#endif  // SERVICES_UI_WS_CURRENT_DRAG_OPERATION_H_