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Eclipse GEF
3.3

org.eclipse.gef
Interface AutoexposeHelper

All Known Implementing Classes:
ViewportAutoexposeHelper

public interface AutoexposeHelper

A helper returned from a GraphicalEditPart. Certain DragTrackers tools and native drop listeners will make use of autoexpose helpers to reveal any potential drop areas that are currently not visible to the user. An example of this is scrolling a container to reveal unexposed area. Another example is a bunch of stacked containers in a "tab folder" arrangement, whever hovering over a tab should switch which container is on top.

Autoexpose helpers are obtained from editparts that are target of whatever operation is being performed. If the target provides no helper, its parent chain is traversed looking for helpers. A helper will be obtained under conditions deemed appropriate by the caller, such as when the mouse has paused for some amount of time in the current location.

An autoexpose helper may be short-lived or long-running. A short-lived helper would be something like the example described above when a "page" is being flipped. A long-running example is auto-scrolling. A helper requests to remains active by returning true from its step(Point) method for as long as necessary. An active helper can remain active even as the mouse is moving. The client may stop calling step(Point) at any time, even if false was never returned, such as when the user releases the mouse.


Nested Class Summary
static class AutoexposeHelper.Search
          Used with EditPartViewers to find the AutoexposeHelper at a Point.
 
Method Summary
 boolean detect ( Point where)
          Returns true if the specified location is interesting to the helper.
 boolean step ( Point where)
          Performs the autoexpose and returns a hint indicating that the helper would like to remain active.
 

Method Detail

detect

public boolean detect(
Point where)
Returns true if the specified location is interesting to the helper. This method gets called as part of the search for an AutoexposeHelper. The helper should do something if it returns true, or it may wait for step(Point) to be called later.

Parameters:
where - the mouse's current location in the viewer
Returns:
true if the location is interesting

step

public boolean step(
Point where)
Performs the autoexpose and returns a hint indicating that the helper would like to remain active. The client will continue to call step() for as long as it previously returned true, and the conditions are deemed appropriate to continue the autoexpose process.

The client may stop calling this method at any time, even if the previous invocation returned true. The return value is a hint.

Parameters:
where - the current location of the mouse in the viewer
Returns:
a hint indicating whether this helper should continue to be invoked

Eclipse GEF
3.3

Copyright (c) IBM Corp. and others 2000, 2007. All Rights Reserved.

 
 
  Published under the terms of the Eclipse Public License Version 1.0 ("EPL") Design by Interspire