On Sun, 23 Jan 2011, Hans-Peter Diettrich wrote:
Michael Van Canneyt schrieb:
i.e. I have used the application-specific DnD, but I wouldn't know how to
handle the intra-app DnD.
Simply start the demo app twice, then drag...
I was thinking about something non-trivial, of course.
Please specify what "non-trivial" use you have in mind, and what results you
expect to see in this very early implementation stage (proof of concetpt).
Drop a piece of text from wordpad on a TMemo. The text should be inserted at
the drop point.
I'd leave all that to the concrete implementations, and provide
specialized handlers in the target controls. Currently TControl.DoDragMsg
dispatches the messages to the Drop and Dock methods, based on the
DragObject class type. More handlers can be added, and dispatch may be
rebased on a drag type (enum) property.
I don't think more handlers should be added. There are too many handlers
already.
That is why you can put the extra information in objects which descend from
TDragObject.
Not only information, but also functionality!
That is what it is for, and it is also the recommended practice in Delphi:
creating a descendant of TDragObject for specific purposes.
Right, and every such Delphi class reacts on dragging events, in its
ProcessMessages method.
The base class (TDragObject) only must declare the extended API, including
common properties.
No, that is IMHO a totally wrong design, which will make the base object
unnecessarily heavy. This is exactly the reason why the API allows you to
create your custom drag object when a drag operation starts: to avoid
putting everything in the base object.
You miss the really essential point: the interface between the drag manager
and the drag object.
I am not missing anything, I am just saying that putting everyting in the
base drag object is not a good decision. I'm not interested in the
implementation details such as dragperformer and whatnot.
I'm interested in how the end-user (the application programmer) sees DnD.
Namely: he can re-use his existing knowledge, there are simply some extra
descendants of TDragObject that implement external file DND and
Inter-application DND, all the rest goes through the same events/methods
that exist now.
How this is accomplished in the background is not so relevant to me; I'm
sure that the people involved will solve it in any way they see fit.
Michael.
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