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Eclipse GEF 2.1 |
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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 return a hint indicating that the helper would like to remain active. |
Method Detail |
public boolean detect(Point where)
true
if the specified location is interesting to the helper. This
method get's 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 interestingpublic boolean 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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Eclipse GEF 2.1 |
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