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Class: DragHandler


Inheritance:

   Object
   |
   +--DragHandler
      |
      +--DragHandler::Generic
      |
      +--DragHandler::Line
      |
      +--DragHandler::Opaque

Package:
stx:libview2
Category:
Interface-DragAndDrop
Version:
rev: 1.19 date: 2017/02/10 10:18:21
user: cg
file: DragHandler.st directory: libview2
module: stx stc-classLibrary: libview2
Author:
Claus Gittinger

Description:


this abstract class describes the protocol common to any DragHandler.
The DragAndDropManger creates one instance responsible to show the
dragging objects on the screen.


Related information:

    DragAndDropManager

Class protocol:

instance creation
o  startArrowDragAt: aStartPoint
creates and returns the drag handler which is responsible
for an arrow drag.

o  startGenericDrag: aTwoArgDragBlock
creates and returns the drag handler which is responsible
for a generic drag.

o  startLineDragAt: aStartPoint
creates and returns the drag handler which is responsible
for a line drag.

o  startOpaqueDrag: aTwoArgDragBlock extent: anExtent offset: anOffset
creates and returns the drag handler which is responsible
for a generic opaque drag.

queries
o  isAbstract
Return if this class is an abstract class.
True is returned here for myself only; false for subclasses.
Abstract subclasses must redefine this again.


Instance protocol:

accessing
o  dropContext

o  dropContext: something

o  targetView

event dropTarget
o  dropTargetWillChange
called before the drop target or widget changed.
restore root view ... (optional)

o  isInterestedInDropTarget
returns true, if the handler is interested in the underlying
drop target and the target should be tested to be able to drop
the objects.

protocol
o  dragTo: aRootPoint
drag to a root point

** This method raises an error - it must be redefined in concrete classes **

o  flushSaveArea

o  postDragging
after dragging; restore root view ...

** This method raises an error - it must be redefined in concrete classes **

o  preDraggingIn: aSourceWidget
called before starting the drag & drop operation

o  rereadSaveArea


Private classes:

    Generic
    Line
    Opaque


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