Delivers drag and drop methods from Surface to DataDevice.

The CL lets Surface observe drag and drop events and delegates the events to
DataDevice thorugh DataDeviceManager.

Bug: b:31988797
Test: None
Change-Id: I9574cd86137922d7527bd297d182a7b45e632c9e
Reviewed-on: https://chromium-review.googlesource.com/579250
Commit-Queue: Daichi Hirono <hirono@chromium.org>
Reviewed-by: David Reveman <reveman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#491951}

components/exo/data_device.cc

@@ -6,13 +6,19 @@
 
 #include "base/logging.h"
 #include "components/exo/data_device_delegate.h"
+#include "components/exo/surface.h"
+#include "ui/base/dragdrop/drag_drop_types.h"
+#include "ui/base/dragdrop/drop_target_event.h"
 
 namespace exo {
 
-DataDevice::DataDevice(DataDeviceDelegate* delegate) : delegate_(delegate) {}
+DataDevice::DataDevice(DataDeviceDelegate* delegate) : delegate_(delegate) {
+  WMHelper::GetInstance()->AddDragDropObserver(this);
+}
 
 DataDevice::~DataDevice() {
   delegate_->OnDataDeviceDestroying(this);
+  WMHelper::GetInstance()->RemoveDragDropObserver(this);
 }
 
 void DataDevice::StartDrag(const DataSource* source_resource,
@@ -28,4 +34,32 @@ void DataDevice::SetSelection(const DataSource* source, uint32_t serial) {
   NOTIMPLEMENTED();
 }
 
+void DataDevice::OnDragEntered(const ui::DropTargetEvent& event) {
+  NOTIMPLEMENTED();
+}
+
+int DataDevice::OnDragUpdated(const ui::DropTargetEvent& event) {
+  NOTIMPLEMENTED();
+  return ui::DragDropTypes::DRAG_NONE;
+}
+
+void DataDevice::OnDragExited() {
+  NOTIMPLEMENTED();
+}
+
+int DataDevice::OnPerformDrop(const ui::DropTargetEvent& event) {
+  NOTIMPLEMENTED();
+  return ui::DragDropTypes::DRAG_NONE;
+}
+
+Surface* DataDevice::GetEffectiveTargetForEvent(
+    const ui::DropTargetEvent& event) const {
+  Surface* target =
+      Surface::AsSurface(static_cast<aura::Window*>(event.target()));
+  if (!target)
+    return nullptr;
+
+  return delegate_->CanAcceptDataEventsForSurface(target) ? target : nullptr;
+}
+
 }  // namespace exo

components/exo/data_device.h

@@ -8,6 +8,11 @@
 #include <cstdint>
 
 #include "base/macros.h"
+#include "components/exo/wm_helper.h"
+
+namespace ui {
+class DropTargetEvent;
+}
 
 namespace exo {
 
@@ -19,10 +24,10 @@ enum class DndAction { kNone, kCopy, kMove, kAsk };
 
 // Data transfer device providing access to inter-client data transfer
 // mechanisms such as copy-and-paste and drag-and-drop.
-class DataDevice {
+class DataDevice : public WMHelper::DragDropObserver {
  public:
   explicit DataDevice(DataDeviceDelegate* delegate);
-  ~DataDevice();
+  ~DataDevice() override;
 
   // Starts drag-and-drop operation.
   // |source| is data source for the eventual transfer or null if data passing
@@ -39,7 +44,15 @@ class DataDevice {
   // selection. |serial| is a unique number of event which tigers SetSelection.
   void SetSelection(const DataSource* source, uint32_t serial);
 
+  // Overridden from WMHelper::DragDropObserver:
+  void OnDragEntered(const ui::DropTargetEvent& event) override;
+  int OnDragUpdated(const ui::DropTargetEvent& event) override;
+  void OnDragExited() override;
+  int OnPerformDrop(const ui::DropTargetEvent& event) override;
+
  private:
+  Surface* GetEffectiveTargetForEvent(const ui::DropTargetEvent& event) const;
+
   DataDeviceDelegate* const delegate_;
 
   DISALLOW_COPY_AND_ASSIGN(DataDevice);

components/exo/data_device_delegate.h

@@ -57,6 +57,10 @@ class DataDeviceDelegate {
   // Called when the data is pasted on the DataDevice.
   virtual void OnSelection(const DataOffer& data_offer) = 0;
 
+  // This should return true if |surface| is a valid target for this data
+  // device. E.g. the surface is owned by the same client as the data device.
+  virtual bool CanAcceptDataEventsForSurface(Surface* surface);
+
  protected:
   virtual ~DataDeviceDelegate() {}
 };

components/exo/wayland/server.cc

@@ -2843,6 +2843,10 @@ class WaylandDataDeviceDelegate : public DataDeviceDelegate {
 
   // Overridden from DataDeviceDelegate:
   void OnDataDeviceDestroying(DataDevice* device) override { delete this; }
+  bool CanAcceptDataEventsForSurface(Surface* surface) override {
+    return surface &&
+           wl_resource_get_client(GetSurfaceResource(surface)) == client_;
+  }
   class DataOffer* OnDataOffer(const std::vector<std::string>& mime_types,
                                const base::flat_set<DndAction>& source_actions,
                                DndAction dnd_action) override {