The TreeView Scrolling Service For Dragging (26 oct 1997)

Author:	Eric Aling
Accessed:
Download:	( treeview.zip 3Kb ):

When you want to drag an object into a treeview, you automatically want the treeview to scroll when needed. This little service provides this functionality.

The service is called n_cst_tvsrv_dragscroll, which is inherited from the PB nonvisual object. I have incorporated this service into my u_tv object as follows:

For u_tv, declare an instance variable inv_DragScroll of type n_cst_tvsrv_DragScroll.
For the DragWithing event code:

if IsValid(inv_DragScroll) then

inv_DragScroll.Event ue_dragwithin(handle)

end if

To start the service, create an objectfunction called of_DragScroll ( ab_switch boolean ) return integer:

if ab_Switch then

if not IsValid(inv_DragScroll) then

inv_DragScroll = create n_cst_tvsrv_DragScroll
inv_DragScroll.of_SetRequestor(This)

end if

else

if IsValid(inv_DragScroll) then

Destroy inv_DragScroll

end if

end if
return 1

Code This.Of_DragScroll(FALSE) in the destructor event of u_tv so that the service will be destroyed ( if needed ) when the treeview control is destroyed.

That's all there is too it. To call the service, just code this.of_DragScroll(TRUE) in the constructor event of your treeview control.

Good luck!