GEOS SDK TechDocs
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2 VisCompClass Instance Data
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3.1 Managing Geometry
With the exception of the geometry flags mentioned above and the management of children, the use of
VisCompClass
is little different from the use of
VisClass
. In fact, most of the functionality designed for
VisCompClass
is built directly into
VisClass
; for example, nearly all geometry management and object tree management messages are defined in
VisClass
. Some reminders are listed below, however.
Not all composite objects will have something to draw. Some composites will be used simply as grouping objects to manage visible children. In these cases, you will not have to subclass
VisCompClass
but can instead use the class directly.
Many composite objects will have something to draw, though. For example, a composite may want to draw a box around its children or wash a different background color behind them. If this is the case, the object must be a subclass of
VisCompClass
and must handle
MSG_VIS_DRAW
.
One of the primary functions of
VisCompClass
is to pass input events and other messages down and up the tree to the proper objects. This is done automatically. You can, however, change this behavior by subclassing
VisCompClass
and intercepting the messages in which the object will be interested.
GEOS SDK TechDocs
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| 2 VisCompClass Instance Data
| 3.1 Managing Geometry