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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 | |
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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 |
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boolean detect(Point where)
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.
where
- the mouse's current location in the viewer
true
if the location is interestingboolean step(Point where)
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.
where
- the current location of the mouse in the viewer
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