Class: DropContext

• Inheritance
• Description
• Class protocol
  • constants
• Instance protocol
  • accessing
  • accessing-source
  • accessing-target
  • actions
  • change & update
  • drag & drop manager interface
  • queries
• Private classes

Inheritance:

   Object
   |
   +--DropContext

Package:

stx:libview2

Category:

Interface-DragAndDrop

Version:

rev: 1.30 date: 2022/07/23 15:16:59

user: cg

file: DropContext.st directory: libview2

module: stx stc-classLibrary: libview2

Description:

instance, which keeps information about the current drag & drop operation.

dropObjects         <Collection>    collection of dropObjects.
rootPoint           <Point>         the current mouse position on the screen (root view).

copyright
COPYRIGHT (c) 1998 by eXept Software AG / Claus Gittinger
             All Rights Reserved

This software is furnished under a license and may be used
only in accordance with the terms of that license and with the
inclusion of the above copyright notice.   This software may not
be provided or otherwise made available to, or used by, any
other person.  No title to or ownership of the software is
hereby transferred.

Class protocol:

 dragTypeCopy

 dragTypeDefault

 dragTypeLink

 dragTypeMove

Instance protocol:

 dragHandler

 dragHandler: aHandler

 dragType

the type of drag - modified by pressing one of Shift, Ctrl or Alt

 dragType: aSymbol

the type of drag - modified by pressing one of Shift, Ctrl or Alt

 dropInfo

a hook for additional info;
can be used for additional attributes/info to be passed around the various
drop-API methods (especially for the widget)

 dropObjects

returns the collection of dropobjects

 manager: something

 rootPoint

returns the current absolute drag position on the screen

 updateDragKindForKeyboardStateOnScreen: aScreen

change the kind of drag operation, when CTRL, META/ALT or SHIFT are pressed
(change from default to dragTypeCopy, dragTypeLink or dragTypeMove)

 dropSource

returns the drop source or nil

 sourcePoint

returns the point in the source widget the drag is started from

 sourceWidget

returns the source widget the drag is started from

 dropTarget

returns the drop target or nil

 targetId

returns the id of the target widget

 targetPoint

returns the point on the target widget (in LOGICAL coordinates).
usually, a dropTarget will ask for this in its canDrop method;
as in:
canDrop:aDropContext
^ myContentsBounds containsPoint:(aDropContext targetPoint)

Usage example(s):

the targetPoint is in LOGICAL coordinates NOT in device coordinates

 targetPointInDeviceCoordinates

returns the point on the target widget (in DEVICE coordinates)

 targetWidget

returns the widget assigned to the current dropTarget

 doDrop

evaluate the drop operation; set the feedBack

 exchangeDragHandler: aHandler

make the new handler to the active handler

 passiveAction: aBlock

 saveDraw: aBlock

evaluate aBlock with the drag temporarily being undrawn
(i.e. restore original picture, evaluate the block, and draw dragged objects again).
Returns the block's value.
Use this, to change the contents while being dragged over,
especially for autoscroll and/or autoexpand/collapse of tree items.

 contentsWillChange

called by the dropTarget-widget if the contents will change during a
dragAndDrop operation.
This must be called before the widget performs
any changes to the view while being dragged over (eg. autoscroll),
to force the d&d operation to restore the view before
(from the bitmap image which it fetched before the opaque move)

 dropObjects: aCollectionOfDropObjects

set the collection of dropobjects

 dropSource: aDropSource

set the dropSource;
that contains information about the drop source

 dropTarget: aDropTargetOrNil

set a new drop target;
that contains information about the drop target (operations)

 rootPoint: aPoint

set the current absolute drag position on the screen (rootPoint);
called by the drag and drop manager

 sourcePoint: aPoint

set the point in the source widget;
that's the widget from which the drag is started from

 sourceWidget: aView

set the source widget;
that's the widget from which the drag is started from

 targetWidget: aViewOrNil id: anId

set a new drop widget (i.e. the widget dragged over)

 canDrop

returns true if the current dropTarget can drop the objects

 clearHasDroppedFlagToSuppressFeedBack

can be used from within a targets drop code,
to signal that no feedBack should be sent to the
dropSource (because the drop did not happen)

 hasDropped

 isAlienView

returns true if current dropTarget is not an ST/X view

 isDragTypeCopy

especially for file-like drags: should the object be copied on drop?

 isDragTypeLink

especially for file-like drags: should the object be linked on drop?

 isDragTypeMove

especially for file-like drags: should the object be moved on drop?

 isRootView

returns true if the current target widget is the root view (screen)

Private classes:

    DragType
    DragTypeCopy
    DragTypeLink
    DragTypeMove