diamant@hpfclp.SDE.HP.COM (John Diamant) (05/05/88)
I would like to set up an event handler for an event on a window that
is not associated with a widget. I know I could replace XtMainLoop
with my own loop including a handler for that event, but that is
ugly. Also, I am trying to hide this code in a library, so requiring
all users of the library to call something other than XtMainLoop is
less than satisfying. From reading both the Toolkit code and the
documentation on this subject, it appears that the only cases in
which the Toolkit will dispatch on an event not tied to a widget is
either an input or timer event or a grab to be sent to a modal
cascade of spring_loaded widgets. None of these sound like they will
do what I want.
Specifically, what I want to do is pay attention to changes in
the RESOURCE_MANAGER property on the root window in order to update
my resources and state variables when it changes, though this is
just an example of the type of thing I'm talking about. I would
like to register an event handler on PropertyChangeMask, but can't
because there is no widget associated with the root window. It seems
to me that Toolkit based window managers would run into similar
problems. Is there some way to do this with the current Toolkit?
Would adding support for this type of callback be reasonable? This
would require storing the list of callbacks in some global place
since they are normally looked up on the widget associated with
the window that got the event. By the way, I'm using X11R2 on an
HP 9000/350.
It appears that there are several types of Event Handler / Callbacks
in the Toolkit, and what I'm interested in would require even another
one. It occurs to me that maybe the approach here is wrong and that
it would be possible to generalize this back down to one or two
types of handlers, though I don't have a specific proposal to do that.
The types of handlers/callbacks I have found are:
1) Event Handlers
2) Callbacks
3) Input Handlers
4) Timer Handlers
5) Event handlers on non-widgets (my addition)
6) Application specific handlers built into other handlers (such
as a dispatcher built into an Input Handler to dispatch on different
functions depending on the type of input).
Thanks in advance,
John Diamant
Software Development Environments
Hewlett-Packard Co. ARPA Internet: diamant@hpfclp.sde.hp.com
Fort Collins, CO UUCP: {hplabs,hpfcla}!hpfclp!diamant