org.eclipse.gef
Interface AutoexposeHelper
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All Known Implementing Classes:
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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.
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Nested Class Summary
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static class
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AutoexposeHelper.Search
Used with EditPartViewers to find the AutoexposeHelper at a Point. |
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Method Summary
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boolean
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detect
(
Point where)
Returns true if the specified location is interesting to the helper. |
boolean
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step
(
Point where)
Performs the autoexpose and returns a hint indicating that the helper would like to
remain active. |
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.
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Parameters:
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where - the mouse's current location in the viewer
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Returns:
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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.
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Parameters:
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where - the current location of the mouse in the viewer
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Returns:
- a hint indicating whether this helper should continue to be invoked
Copyright (c) IBM Corp. and others 2000, 2007. All Rights Reserved.
