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// Copyright 2018 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef UI_PLATFORM_WINDOW_WM_WM_DRAG_HANDLER_H_
#define UI_PLATFORM_WINDOW_WM_WM_DRAG_HANDLER_H_
#include <optional>
#include "base/component_export.h"
#include "base/functional/callback.h"
#include "ui/base/dragdrop/mojom/drag_drop_types.mojom-forward.h"
#include "ui/gfx/geometry/vector2d.h"
#include "ui/gfx/image/image_skia.h"
#include "ui/gfx/native_widget_types.h"
namespace gfx {
class Point;
}
namespace ui {
class PlatformWindow;
class OSExchangeData;
class COMPONENT_EXPORT(WM) WmDragHandler {
public:
// Notifies when the drag operation finished.
using DragFinishedCallback =
base::OnceCallback<void(mojom::DragOperation operation)>;
// A delegate class for a platform on which chrome manages a drag image and
// needs to receive the drag location. This can be null if the platform itself
// manages the drag image.
class LocationDelegate {
public:
// Called every time when the drag location has changed.
virtual void OnDragLocationChanged(const gfx::Point& screen_point_px) = 0;
// Called when the currently negotiated operation has changed.
virtual void OnDragOperationChanged(mojom::DragOperation operation) = 0;
// DragWidget (if any) should be ignored when finding top window and
// dispatching mouse events.
virtual std::optional<gfx::AcceleratedWidget> GetDragWidget() = 0;
protected:
virtual ~LocationDelegate();
};
// Starts dragging `data`. Whereas, `operations` is a bitmask of
// DragDropTypes::DragOperation values, which defines possible operations for
// the drag source. The destination sets the resulting operation when the drop
// action is performed. `source` indicates the source event type triggering
// the drag, and `can_grab_pointer` indicates whether the implementation can
// grab the mouse pointer (some platforms may need this). In progress updates
// on the drag operation come back through the `location_delegate` on the
// platform that chrome needs manages a drag image). This can be null if the
// platform manages a drag image. `drag_started_callback` is called after the
// request to start the drag was sent to the OS (see below for details), and
// `drag_finished_callback` is called when drag operation finishes. These
// callbacks are necessary because of the nested message loop (see below).
//
// `drag_started_callback` is called if and only if the drag actually starts.
// If initialization fails and the drag doesn't start, it will not be called.
// Also note that it might be called even when this method returns false if
// the drag does start but is cancelled later on.
//
// This method runs a nested message loop, returning when the drag operation
// is done. Care must be taken when calling this as it's entirely possible
// that when this returns this object (and the calling object) have been
// destroyed.
//
// Returns whether the operation ended well (i.e., had not been canceled).
virtual bool StartDrag(const OSExchangeData& data,
int operations,
mojom::DragEventSource source,
gfx::NativeCursor cursor,
bool can_grab_pointer,
base::OnceClosure drag_started_callback,
DragFinishedCallback drag_finished_callback,
LocationDelegate* location_delegate) = 0;
// Cancels the drag.
virtual void CancelDrag() = 0;
// Updates the drag image. An empty |image| may be used to hide a previously
// set non-empty drag image, and a non-empty |image| shows the drag image
// again if it was previously hidden.
//
// This must be called during an active drag session.
virtual void UpdateDragImage(const gfx::ImageSkia& image,
const gfx::Vector2d& offset) = 0;
// Returns whether capture should be released before a StartDrag() call.
virtual bool ShouldReleaseCaptureForDrag(ui::OSExchangeData* data) const;
};
COMPONENT_EXPORT(WM)
void SetWmDragHandler(PlatformWindow* platform_window,
WmDragHandler* drag_handler);
COMPONENT_EXPORT(WM)
WmDragHandler* GetWmDragHandler(const PlatformWindow& platform_window);
} // namespace ui
#endif // UI_PLATFORM_WINDOW_WM_WM_DRAG_HANDLER_H_
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