Filter (filter)
Overlays its child with reactivity.
- Cursor
- (Text)
Names the cursor that will be displayed
when the mouse is over the child. The default is cursor is defined by
the Trestle implementation.
- Reactivity choices (mutually exclusive):
- Active
- (Boolean, TRUE)
When true,
mouse and keyboard events are relayed to child. This is the normal case.
- Passive
- (Boolean, FALSE)
When true, doesn't
allow mouse or keyboard events to go to the child; in
addition, the cursor is changed to Cursor.NotReady, a watch-face.
- Dormant
- (Boolean, FALSE)
When true, doesn't send
mouse or keyboard events to the child; it also draws a grey screen
over the child.
- Vanish
- (Boolean, FALSE)
When true, doesn't
send mouse or keyboard events to the child; in addition,
it draws over the child in the background color
thereby making it invisible.
- Shape
- The shape of its child.
- Notes
- Of the four state properties, exactly one can be in effect at
any instant. If more than one is specified, they are considered in
the order Vanish, Dormant, Passive, and
Active to find the first one that is true. If all are false
(including Active, which defaults to true), an error is raised.
To test the reactivity of a Filter, you can call one of the following
procedures in the FormsVBT interface: IsActive,
IsPassive, IsDormant, or IsVanished. To change
the reactivity or the cursor, call MakeActive,
MakePassive, MakeDormant, or MakeVanish.
FormsVBT provides a mechanism for accessing the nearest Filter
component above a named interactor. Thus, Filter interactors are
typically left unnamed, and some named descendant is used to reference
the Filter from the application program.
As mentioned, the default is cursor is defined by the Trestle
implementation. Standard X screentypes support the cursors named in
X Window System by Scheifler et. al. [XWindowSystem] Appendix B.
Therefore, for example, XC_arrow returns a cursor that behaves
like the X arrow cursor on X screentypes, and like the default cursor
on screentypes that have no cursor named XC_arrow. *)