mus: Implement interwindow drag and drop

services/ui/ws/window_tree.cc

 // Copyright 2014 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 "services/ui/ws/window_tree.h"
 
 #include <stddef.h>
 
 #include <utility>
 
@@ skipping 1369 matching lines @@
     DVLOG(1) << "SetHitTestMask failed";
     return;
   }
 
   if (mask)
     window->SetHitTestMask(*mask);
   else
     window->ClearHitTestMask();
 }
 
+void WindowTree::SetCanAcceptDrops(Id window_id, bool accepts_drops) {
+  ServerWindow* window = GetWindowByClientId(ClientWindowId(window_id));
+  if (!window || !access_policy_->CanSetAcceptDrops(window)) {
+    DVLOG(1) << "SetAcceptsDrops failed";
+    return;
+  }
+
+  window->SetCanAcceptDrops(accepts_drops);
+}
+
 void WindowTree::Embed(Id transport_window_id,
                        mojom::WindowTreeClientPtr client,
                        uint32_t flags,
                        const EmbedCallback& callback) {
   callback.Run(
       Embed(ClientWindowId(transport_window_id), std::move(client), flags));
 }
 
 void WindowTree::SetFocus(uint32_t change_id, Id transport_window_id) {
   client()->OnChangeCompleted(change_id,
@@ skipping 45 matching lines @@
           this, std::move(internal)));
 }
 
 void WindowTree::GetCursorLocationMemory(
     const GetCursorLocationMemoryCallback& callback) {
   callback.Run(
       window_server_->display_manager()->GetUserDisplayManager(user_id_)->
       GetCursorLocationMemory());
 }
 
+void WindowTree::PerformDragDrop(
+    uint32_t change_id,
+    uint32_t source_window_id,

[sky, 2016/09/13 18:15:32]

uint32_t -> Id

+    int32_t drag_pointer,
+    mojo::Map<mojo::String, mojo::Array<uint8_t>> drag_data,
+    uint32_t drag_operation) {
+  ServerWindow* window = GetWindowByClientId(ClientWindowId(source_window_id));
+  bool success = window && access_policy_->CanInitiateMoveLoop(window);

[sky, 2016/09/13 18:15:32]

Please add a new function, CanInitiateDragLoop?

+  if (!success || !ShouldRouteToWindowManager(window)) {
+    // We need to fail this move loop change, otherwise the client will just be
+    // waiting for |change_id|.
+    OnChangeCompleted(change_id, false);

[sky, 2016/09/13 18:15:32]

Please DVLOG the failures.

+    return;
+  }
+
+  WindowManagerDisplayRoot* display_root = GetWindowManagerDisplayRoot(window);
+  if (!display_root) {
+    // The window isn't parented. There's nothing to do.
+    OnChangeCompleted(change_id, false);
+    return;
+  }
+
+  if (window_server_->in_move_loop() || window_server_->in_drag_loop()) {
+    // Either the window manager is servicing a window drag or we're servicing
+    // a drag and drop operation. We can't start a second drag.
+    OnChangeCompleted(change_id, false);
+    return;
+  }
+
+  // TODO(erg): Dealing with |drag_representation| is hard, so we're going to
+  // deal with that later.
+
+  // Here, we need to dramatically change how the mouse pointer works. Once
+  // we've started a drag drop operation, cursor events don't go to windows as
+  // normal.
+  WindowManagerState* wms = display_root->window_manager_state();
+  window_server_->StartDragLoop(change_id, window, this);
+  wms->SetDragDropSourceWindow(this, window, this, drag_pointer,

[sky, 2016/09/13 18:15:32]

optional: it's mildly weird that WindowServer::StartDropLoop doesn't call
wms->SetDragDropSourceWindow. In other words, it's weird the StartDragLoop
doesn't start anything.

+                               std::move(drag_data), drag_operation);
+}
+
 void WindowTree::PerformWindowMove(uint32_t change_id,
                                    Id window_id,
                                    ui::mojom::MoveLoopSource source,
                                    const gfx::Point& cursor) {
   ServerWindow* window = GetWindowByClientId(ClientWindowId(window_id));
   bool success = window && access_policy_->CanInitiateMoveLoop(window);
   if (!success || !ShouldRouteToWindowManager(window)) {
     // We need to fail this move loop change, otherwise the client will just be
     // waiting for |change_id|.
     OnChangeCompleted(change_id, false);
     return;
   }
 
   WindowManagerDisplayRoot* display_root = GetWindowManagerDisplayRoot(window);
   if (!display_root) {
     // The window isn't parented. There's nothing to do.
     OnChangeCompleted(change_id, false);
     return;
   }
 
-  if (window_server_->in_move_loop()) {
-    // A window manager is already servicing a move loop; we can't start a
-    // second one.
+  if (window_server_->in_move_loop() || window_server_->in_drag_loop()) {
+    // Either the window manager is servicing a window drag or we're servicing
+    // a drag and drop operation. We can't start a second drag.
     OnChangeCompleted(change_id, false);
     return;
   }
 
   // When we perform a window move loop, we give the window manager non client
   // capture. Because of how the capture public interface currently works,
   // SetCapture() will check whether the mouse cursor is currently in the
   // non-client area and if so, will redirect messages to the window
   // manager. (And normal window movement relies on this behaviour.)
   WindowManagerState* wms = display_root->window_manager_state();
@@ skipping 186 matching lines @@
     const ServerWindow* window) const {
   return IsWindowKnown(window);
 }
 
 bool WindowTree::IsWindowRootOfAnotherTreeForAccessPolicy(
     const ServerWindow* window) const {
   WindowTree* tree = window_server_->GetTreeWithRoot(window);
   return tree && tree != this;
 }
 
+void WindowTree::OnDragCompleted(bool success) {
+  DCHECK(window_server_->in_drag_loop());
+  DCHECK_EQ(this, window_server_->GetCurrentDragLoopInitiator());
+
+  uint32_t change_id = window_server_->GetCurrentDragLoopChangeId();
+  ServerWindow* window = window_server_->GetCurrentDragLoopWindow();
+  WindowManagerDisplayRoot* display_root = GetWindowManagerDisplayRoot(window);
+  if (!display_root)
+    return;
+
+  window_server_->EndDragLoop();
+  WindowManagerState* wms = display_root->window_manager_state();
+  wms->EndDragDrop();
+
+  client()->OnChangeCompleted(change_id, success);
+}
+
+ServerWindow* WindowTree::GetWindowById(const WindowId& id) {
+  return GetWindow(id);
+}
+
+DragTargetConnection* WindowTree::GetDragTargetWithRoot(
+    const ServerWindow* window) {
+  return window_server_->GetTreeWithRoot(window);

[sky, 2016/09/13 18:15:32]

This returns the WindowTree that has |window| as one if it's root. That's fine
for the embed point, but not for windows that aren't embedded. If
GetTreeWithRoot returns null you should fallback to the tree that created the
window.

+}
+
+void WindowTree::PerformOnDragMimeTypes(
+    mojo::Map<mojo::String, mojo::Array<uint8_t>> mime_data) {
+  client()->OnDragMimeTypes(std::move(mime_data));
+}
+
+void WindowTree::PerformOnDragEnter(
+    const ServerWindow* window,
+    uint32_t event_flags,
+    const gfx::Point& cursor_offset,
+    uint32_t effect_bitmask,
+    const base::Callback<void(uint32_t)>& callback) {
+  ClientWindowId client_window_id;
+  if (!IsWindowKnown(window, &client_window_id)) {
+    NOTREACHED();
+    callback.Run(0);
+    return;
+  }
+  client()->OnDragEnter(client_window_id.id, event_flags, cursor_offset,
+                        effect_bitmask, callback);
+}
+
+void WindowTree::PerformOnDragOver(
+    const ServerWindow* window,
+    uint32_t event_flags,
+    const gfx::Point& cursor_offset,
+    uint32_t effect_bitmask,
+    const base::Callback<void(uint32_t)>& callback) {
+  ClientWindowId client_window_id;
+  if (!IsWindowKnown(window, &client_window_id)) {
+    NOTREACHED();
+    callback.Run(0);
+    return;
+  }
+  client()->OnDragOver(client_window_id.id, event_flags, cursor_offset,
+                       effect_bitmask, callback);
+}
+
+void WindowTree::PerformOnDragLeave(const ServerWindow* window) {
+  ClientWindowId client_window_id;
+  if (!IsWindowKnown(window, &client_window_id)) {
+    NOTREACHED();
+    return;
+  }
+  client()->OnDragLeave(client_window_id.id);
+}
+
+void WindowTree::PerformOnCompleteDrop(
+    const ServerWindow* window,
+    uint32_t event_flags,
+    const gfx::Point& cursor_offset,
+    uint32_t effect_bitmask,
+    const base::Callback<void(uint32_t)>& callback) {
+  ClientWindowId client_window_id;
+  if (!IsWindowKnown(window, &client_window_id)) {
+    NOTREACHED();
+    callback.Run(0);
+    return;
+  }
+  client()->OnCompleteDrop(client_window_id.id, event_flags, cursor_offset,
+                           effect_bitmask, callback);
+}
+
+void WindowTree::PerformOnDragFinish() {
+  client()->OnDragFinish();
+}
+
 }  // namespace ws
 }  // namespace ui