mus: Implement interwindow drag and drop

services/ui/ws/drag_target_connection.h

+// 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_DRAG_TARGET_CONNECTION_H_
+#define SERVICES_UI_WS_DRAG_TARGET_CONNECTION_H_
+
+#include "base/bind.h"
+#include "mojo/public/cpp/bindings/array.h"
+#include "mojo/public/cpp/bindings/map.h"
+#include "mojo/public/cpp/bindings/string.h"
+#include "ui/gfx/geometry/point.h"
+
+namespace ui {
+namespace ws {
+
+class ServerWindow;
+
+// An abstract connection which can respond to drag/drop target requests.
+//
+// The methods in this class send drag and drop messages to the client and
+// return their results through the passed in callback.
+class DragTargetConnection {
+ public:
+  virtual ~DragTargetConnection() {}
+
+  virtual void PerformOnDragStart(
+      const ServerWindow* window,
+      mojo::Map<mojo::String, mojo::Array<uint8_t>> mime_data) = 0;
+
+  virtual void PerformOnDragEnter(
+      const ServerWindow* window,
+      uint32_t key_state,
+      const gfx::Point& cursor_offset,
+      uint32_t effect_bitmask,
+      const base::Callback<void(uint32_t)>& callback) = 0;
+
+  virtual void PerformOnDragOver(
+      const ServerWindow* window,
+      uint32_t key_state,
+      const gfx::Point& cursor_offset,
+      uint32_t effect_bitmask,
+      const base::Callback<void(uint32_t)>& callback) = 0;
+
+  virtual void PerformOnDragLeave(const ServerWindow* window) = 0;
+
+  virtual void PerformOnDragDrop(
+      const ServerWindow* window,
+      uint32_t key_state,
+      const gfx::Point& cursor_offset,
+      uint32_t effect_bitmask,
+      const base::Callback<void(uint32_t)>& callback) = 0;
+
+  virtual void PerformOnDragFinish(const ServerWindow* window) = 0;

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

Document when this is sent. It isn't clear how it relates to PerformOnDRagLeave
and PerformOnDragDrop. What would actually help is class level doc that
describes the cycle.

+};
+
+}  // namespace ws
+}  // namespace ui
+
+#endif  // SERVICES_UI_WS_DRAG_TARGET_CONNECTION_H_