Initial release

engine/vendor/vst3sdk/vstgui4/vstgui/lib/dragging.h

@@ -0,0 +1,241 @@
+// This file is part of VSTGUI. It is subject to the license terms
+// in the LICENSE file found in the top-level directory of this
+// distribution and at http://github.com/steinbergmedia/vstgui/LICENSE
+
+#pragma once
+
+#include "vstguifwd.h"
+#include "cbitmap.h"
+#include "events.h"
+#include "cpoint.h"
+#include "idatapackage.h"
+#include <functional>
+
+//------------------------------------------------------------------------
+namespace VSTGUI {
+
+//------------------------------------------------------------------------
+/** Drag description
+ *
+ *	@ingroup new_in_4_7
+ */
+struct DragDescription
+{
+	SharedPointer<IDataPackage> data;
+	SharedPointer<CBitmap> bitmap;
+	CPoint bitmapOffset;
+
+	explicit DragDescription (const SharedPointer<IDataPackage>& data,
+	                          CPoint bitmapOffset = CPoint (),
+	                          const SharedPointer<CBitmap>& bitmap = nullptr)
+	: data (data), bitmap (bitmap), bitmapOffset (bitmapOffset)
+	{
+	}
+};
+
+//------------------------------------------------------------------------
+/** Drag operation
+ *
+ *	@ingroup new_in_4_7
+ */
+enum class DragOperation
+{
+	/** the drag will be or was copied*/
+	Copy,
+	/** the drag will be or was moved*/
+	Move,
+	/** no drag operation will occure or was happening */
+	None
+};
+
+//------------------------------------------------------------------------
+/** Dragging session interface
+ *
+ *	@ingroup new_in_4_7
+ */
+class IDraggingSession
+{
+public:
+	virtual bool setBitmap (const SharedPointer<CBitmap>& bitmap, CPoint offset) = 0;
+};
+
+//------------------------------------------------------------------------
+/** Drag event data
+ *
+ *	@ingroup new_in_4_7
+ */
+struct DragEventData
+{
+	/** drag data package */
+	IDataPackage* drag;
+	/** mouse position */
+	CPoint pos;
+	/** key modifiers */
+	Modifiers modifiers;
+};
+
+//------------------------------------------------------------------------
+/** Drop target interface
+ *
+ *	handles drag'n drop for a view
+ *
+ *	The workflow is:
+ *
+ *	- drag enters a view, the @b getDropTarget() of the view is called
+ *
+ *	- the drop targets @b onDragEnter() is called
+ *
+ *	- the drop targets @b onDragMove() is called whenever the mouse moves inside the view
+ *
+ *	- when the mouse leaves the view, the drop targets @b onDragLeave() is called and its reference
+ *		count is decreased.
+ *
+ *	- when the drag is droped, the drop targets @b onDrop() is called and then its reference count
+ *		is decreased. Note that no @b onDragLeave() is called.
+ *
+ *	@ingroup new_in_4_7
+ */
+class IDropTarget : virtual public IReference
+{
+public:
+	/** a drag enters the drop target
+	 *	@param data drag event data
+	 *	@return drag operation
+	 */
+	virtual DragOperation onDragEnter (DragEventData data) = 0;
+	/** a drag moves over the drop target
+	 *	@param data drag event data
+	 *	@return drag operation
+	 */
+	virtual DragOperation onDragMove (DragEventData data) = 0;
+	/** a drag leaves the drop target
+	 *	@param data drag event data
+	 */
+	virtual void onDragLeave (DragEventData data) = 0;
+	/** a drop happens on the drop target
+	 *	@param data drag event data
+	 */
+	virtual bool onDrop (DragEventData data) = 0;
+};
+
+//------------------------------------------------------------------------
+/** Drag callback interface
+ *
+ *	An optional interface to be used when initiating a drag to know where the mouse is and what the
+ *	result of the drag was.
+ *
+ *	@ingroup new_in_4_7
+ */
+class IDragCallback : virtual public IReference
+{
+public:
+	/** the drag will begin
+	 *	@param session dragging session
+	 *	@param pos drag position in CFrame coordinates
+	 */
+	virtual void dragWillBegin (IDraggingSession* session, CPoint pos) = 0;
+	/** the drag was moved
+	 *	@param session dragging session
+	 *	@param pos drag position in CFrame coordinates
+	 */
+	virtual void dragMoved (IDraggingSession* session, CPoint pos) = 0;
+	/** the drag ended
+	 *	@param session dragging session
+	 *	@param pos drag position in CFrame coordinates
+	 *	@param result the result of the drag
+	 */
+	virtual void dragEnded (IDraggingSession* session, CPoint pos, DragOperation result) = 0;
+};
+
+//------------------------------------------------------------------------
+/** Drag callback interface adapter
+ *
+ *	@ingroup new_in_4_7
+ */
+class DragCallbackAdapter : virtual public IDragCallback
+{
+public:
+	void dragWillBegin (IDraggingSession* session, CPoint pos) override {}
+	void dragMoved (IDraggingSession* session, CPoint pos) override {}
+	void dragEnded (IDraggingSession* session, CPoint pos, DragOperation result) override {}
+};
+
+//------------------------------------------------------------------------
+/** Drag callback interface adapter which calls std::functions
+ *
+ *	@ingroup new_in_4_7
+ */
+class DragCallbackFunctions : virtual public IDragCallback, public NonAtomicReferenceCounted
+{
+public:
+	using Func1 = std::function<void (IDraggingSession*, CPoint)>;
+	using Func2 = std::function<void (IDraggingSession*, CPoint, DragOperation)>;
+
+	DragCallbackFunctions () = default;
+
+	void dragWillBegin (IDraggingSession* session, CPoint pos) override
+	{
+		if (willBeginFunc)
+			willBeginFunc (session, pos);
+	}
+	void dragMoved (IDraggingSession* session, CPoint pos) override
+	{
+		if (movedFunc)
+			movedFunc (session, pos);
+	}
+	void dragEnded (IDraggingSession* session, CPoint pos, DragOperation result) override
+	{
+		if (endedFunc)
+			endedFunc (session, pos, result);
+	}
+
+	Func1 willBeginFunc;
+	Func1 movedFunc;
+	Func2 endedFunc;
+};
+
+//------------------------------------------------------------------------
+/** Drop target interface adapter
+ *
+ *	@ingroup new_in_4_7
+ */
+class DropTargetAdapter : virtual public IDropTarget
+{
+public:
+	DragOperation onDragEnter (DragEventData eventData) override { return DragOperation::None; }
+	DragOperation onDragMove (DragEventData eventData) override { return DragOperation::None; }
+	void onDragLeave (DragEventData eventData) override {}
+	bool onDrop (DragEventData eventData) override { return false; }
+};
+
+//------------------------------------------------------------------------
+/** Helper method to be used to decide if a mouse move is far enough to start a drag operation.
+ *	\sa DragStartMouseObserver
+ *
+ *	@ingroup new_in_4_9
+ */
+inline bool shouldStartDrag (CPoint mouseDownPos, CPoint mouseMovePos)
+{
+	constexpr auto minDiff = 4;
+	return (std::abs (mouseDownPos.x - mouseMovePos.x) >= minDiff ||
+	        std::abs (mouseDownPos.y - mouseMovePos.y) >= minDiff);
+}
+
+//------------------------------------------------------------------------
+/** Helper object to be used to decide if a mouse move is far enough to start a drag operation
+ *	\sa shouldStartDrag
+ *
+ *	@ingroup new_in_4_9
+ */
+struct DragStartMouseObserver
+{
+	void init (CPoint mousePos) { pos = mousePos; }
+	bool shouldStartDrag (CPoint mousePos) const { return VSTGUI::shouldStartDrag (pos, mousePos); }
+
+	CPoint getInitPosition () const { return pos; }
+private:
+	CPoint pos {};
+};
+
+//------------------------------------------------------------------------
+} // VSTGUI