mus: Implement interwindow drag and drop

ui/views/mus/native_widget_mus.cc

Index: ui/views/mus/native_widget_mus.cc
diff --git a/ui/views/mus/native_widget_mus.cc b/ui/views/mus/native_widget_mus.cc
index c98fa9069cae6021d5ddbccf1c0f4f39080412aa..05460dde0e5eef1b0c2ef053454a37788d8f6b70 100644
--- a/ui/views/mus/native_widget_mus.cc
+++ b/ui/views/mus/native_widget_mus.cc
@@ -32,9 +32,12 @@
 #include "ui/gfx/path.h"
 #include "ui/native_theme/native_theme_aura.h"
 #include "ui/platform_window/platform_window_delegate.h"
+#include "ui/views/mus/drop_target_mus.h"
+#include "ui/views/mus/os_exchange_data_provider_mus.h"
 #include "ui/views/mus/window_manager_constants_converters.h"
 #include "ui/views/mus/window_manager_frame_values.h"
 #include "ui/views/mus/window_tree_host_mus.h"
+#include "ui/views/widget/drop_helper.h"
 #include "ui/views/widget/native_widget_aura.h"
 #include "ui/views/widget/widget_delegate.h"
 #include "ui/views/window/custom_frame_view.h"
@@ -522,6 +525,7 @@ NativeWidgetMus::NativeWidgetMus(internal::NativeWidgetDelegate* delegate,
       show_state_before_fullscreen_(ui::mojom::ShowState::DEFAULT),
       ownership_(Widget::InitParams::NATIVE_WIDGET_OWNS_WIDGET),
       content_(new aura::Window(this)),
+      last_drop_operation_(ui::DragDropTypes::DRAG_NONE),
       close_widget_factory_(this) {
   window_->set_input_event_handler(this);
   mus_window_observer_.reset(new MusWindowObserver(this));
@@ -696,6 +700,13 @@ void NativeWidgetMus::InitNativeWidget(const Widget::InitParams& params) {
   aura::client::SetScreenPositionClient(hosted_window,
                                         screen_position_client_.get());
 
+  // TODO(erg): Create and call CreateDragDropClient() here for maximum aura.
+
+  drop_target_.reset(new DropTargetMus(content_));
+  window_->SetCanAcceptDrags(drop_target_.get());
+  drop_helper_.reset(new DropHelper(GetWidget()->GetRootView()));
+  aura::client::SetDragDropDelegate(content_, this);
+
   // TODO(erg): Remove this check when ash/mus/move_event_handler.cc's
   // direct usage of ui::Window::SetPredefinedCursor() is switched to a
   // private method on WindowManagerClient.
@@ -1117,13 +1128,33 @@ void NativeWidgetMus::FlashFrame(bool flash_frame) {
   // NOTIMPLEMENTED();
 }
 
-void NativeWidgetMus::RunShellDrag(
-    View* view,
-    const ui::OSExchangeData& data,
-    const gfx::Point& location,
-    int operation,
-    ui::DragDropTypes::DragEventSource source) {
-  // NOTIMPLEMENTED();
+void NativeWidgetMus::RunShellDrag(View* view,
+                                   const ui::OSExchangeData& data,
+                                   const gfx::Point& location,
+                                   int drag_operations,
+                                   ui::DragDropTypes::DragEventSource source) {
+  ReleaseCapture();
+
+  base::MessageLoopForUI* loop = base::MessageLoopForUI::current();
+  base::MessageLoop::ScopedNestableTaskAllower allow_nested(loop);
+  base::RunLoop run_loop;
+
+  std::map<std::string, std::vector<uint8_t>> drag_data =
+      static_cast<const OSExchangeDataProviderMus&>(data.provider()).GetData();
+
+  // TODO(erg): Right now, I'm passing the cursor_location, but maybe I want to
+  // pass OSExchangeData::GetDragImageOffset() instead?
+
+  bool success = false;
+  gfx::Point cursor_location = location;
+  window_->PerformDragDrop(
+      drag_data, drag_operations, cursor_location,
+      *data.provider().GetDragImage().bitmap(),
+      base::Bind(OnMoveLoopEnd, &success, run_loop.QuitClosure()));
+
+  run_loop.Run();
+
+  // In the aura version, we just throw the return code away.
 }
 
 void NativeWidgetMus::SchedulePaintInRect(const gfx::Rect& rect) {
@@ -1377,6 +1408,38 @@ void NativeWidgetMus::OnHostCloseRequested(const aura::WindowTreeHost* host) {
   GetWidget()->Close();
 }
 
+////////////////////////////////////////////////////////////////////////////////
+// NativeWidgetMus, aura::WindowDragDropDelegate implementation:
+
+void NativeWidgetMus::OnDragEntered(const ui::DropTargetEvent& event) {
+  DCHECK(drop_helper_);
+  last_drop_operation_ = drop_helper_->OnDragOver(
+      event.data(), event.location(), event.source_operations());
+}
+
+int NativeWidgetMus::OnDragUpdated(const ui::DropTargetEvent& event) {
+  DCHECK(drop_helper_);
+  last_drop_operation_ = drop_helper_->OnDragOver(
+      event.data(), event.location(), event.source_operations());
+  return last_drop_operation_;
+}
+
+void NativeWidgetMus::OnDragExited() {
+  DCHECK(drop_helper_);
+  drop_helper_->OnDragExit();
+}
+
+int NativeWidgetMus::OnPerformDrop(const ui::DropTargetEvent& event) {
+  DCHECK(drop_helper_);
+  // if (ShouldActivate())
+  //   Activate();
+  return drop_helper_->OnDrop(event.data(), event.location(),
+                              last_drop_operation_);
+}
+
+////////////////////////////////////////////////////////////////////////////////
+// NativeWidgetMus, ui::InputEventHandler implementation:
+
 void NativeWidgetMus::OnWindowInputEvent(
     ui::Window* view,
     const ui::Event& event_in,