Drag & drop implementation at GHOST level (only OSX for now)

The dragging sequence is performed in four phases:
 
- Start sequence (GHOST_kEventDraggingEntered) that tells a drag'n'drop operation has started. Already gives the object data type, and the entering mouse location

- Update mouse position (GHOST_kEventDraggingUpdated) sent upon each mouse move until the drag'n'drop operation stops, to give the updated mouse position.
Useful to highlight a potential destination, and update the status (through GHOST_setAcceptDragOperation) telling if the object can be dropped at the current cursor position.

- Abort drag'n'drop sequence (GHOST_kEventDraggingExited) sent when the user moved the mouse outside the window.

- Send the dropped data (GHOST_kEventDraggingDropDone)

- Outside of the normal sequence, dropped data can be sent (GHOST_kEventDraggingDropOnIcon). This can happen when the user drops an object on the application icon. (Also used in OSX to pass the filename of the document the user doubled-clicked in the finder)

Note that the event handler is responsible for freeing the received data.
And the mouse position is sent directly in blender client coordinates (y=0 at bottom)

The GHOST_setAcceptDragOperation(TRUE) call must be placed before the user drops the object for it to be accepted.

Current handled data types :
- Text string
- Array of filenames (full paths)
- Bitmap image (not implemented yet)

1 files changed, 11 insertions, 0 deletions

diff --git a/intern/ghost/GHOST_C-api.h b/intern/ghost/GHOST_C-api.h
index bd812177f17..5e434c0eaa0 100644
--- a/intern/ghost/GHOST_C-api.h
+++ b/intern/ghost/GHOST_C-api.h
@@ -406,6 +406,17 @@ extern GHOST_TSuccess GHOST_GetButtonState(GHOST_SystemHandle systemhandle,
 										   GHOST_TButtonMask mask,
 										   int* isDown);
 
+
+/***************************************************************************************
+ ** Drag'n'drop operations
+ ***************************************************************************************/
+
+/**
+ * Tells if the ongoing drag'n'drop object can be accepted upon mouse drop
+ */
+extern void GHOST_setAcceptDragOperation(GHOST_SystemHandle systemhandle, GHOST_TInt8 canAccept);
+	
+	
 /**
  * Returns the event type.
  * @param eventhandle The handle to the event