tom@capella.ucsb.edu (Tom Weinstein) (02/15/90)
I'm trying to process events using the X toolkit in a way that will not
block when the queue is empty. This is what I'm doing:
XEvent event;
while (XtAppPending(context)) {
XtAppNextEvent(context, &event);
XtDispatchEvent(&event);
}
However, this seems to block when there are no events in the queue. Am
I doing something wrong, or is this a bug?
--
It does not do to leave a dragon | Tom Weinstein ...ucbvax!hub!ucsbuxa!6600tom
out of your calculations, if you | 6600tom@ucsbuxa.bitnet tom@bears.ucsb.edu
live near him. --J.R.R. Tolkien | 6600tom@ucsbuxa.ucsb.edu tomw@cornu.ucsb.eduasente@decwrl.dec.com (Paul Asente) (02/15/90)
In article <3947@hub.UUCP> tom@bears.ucsb.edu writes: >I'm trying to process events using the X toolkit in a way that will not >block when the queue is empty. This is what I'm doing: > > XEvent event; > > while (XtAppPending(context)) { > XtAppNextEvent(context, &event); > XtDispatchEvent(&event); > } > >However, this seems to block when there are no events in the queue. Am >I doing something wrong, or is this a bug? Are you using timers or alternate input sources? XtAppPending returns non-zero when these exist but XtAppNextEvent still blocks if there are no X events. If this is the case, you might try while (XtAppPending(context) & XtIMXEvent) { ... The Intrinsics will add timers themselves if you or the widgets use the selection mechanism. The widgets may be adding timers themselves. -paul asente asente@decwrl.dec.com decwrl!asente
tom@capella.ucsb.edu (Tom Weinstein) (02/15/90)
In article <2759@bacchus.dec.com> asente@decwrl.dec.com (Paul Asente) writes: In article <3947@hub.UUCP> tom@bears.ucsb.edu writes: >> while (XtAppPending(context)) { >> XtAppNextEvent(context, &event); >> XtDispatchEvent(&event); >> } >> However, this seems to block when there are no events in the queue. Am >> I doing something wrong, or is this a bug? > Are you using timers or alternate input sources? XtAppPending returns > non-zero when these exist but XtAppNextEvent still blocks if there are no > X events. If this is the case, you might try Yes, I am using timers. > while (XtAppPending(context) & XtIMXEvent) { > ... Okay, but if I do this, doesn't that mean that none of my timer events will get processed? > -paul asente > asente@decwrl.dec.com decwrl!asente -- It does not do to leave a dragon | Tom Weinstein ...ucbvax!hub!ucsbuxa!6600tom out of your calculations, if you | 6600tom@ucsbuxa.bitnet tom@bears.ucsb.edu live near him. --J.R.R. Tolkien | 6600tom@ucsbuxa.ucsb.edu tomw@cornu.ucsb.edu
tom@capella.ucsb.edu (Tom Weinstein) (02/15/90)
In article <2759@bacchus.dec.com> asente@decwrl.dec.com (Paul Asente) writes: In article <3947@hub.UUCP> tom@bears.ucsb.edu writes: >> XEvent event; >> >> while (XtAppPending(context)) { >> XtAppNextEvent(context, &event); >> XtDispatchEvent(&event); >> } >>However, this seems to block when there are no events in the queue. Am >>I doing something wrong, or is this a bug? >Are you using timers or alternate input sources? XtAppPending returns >non-zero when these exist but XtAppNextEvent still blocks if there are no >X events. If this is the case, you might try > while (XtAppPending(context) & XtIMXEvent) { > ... I just figured out the right way to do this: XEvent event; XtInputMask mask; XFlush(XtDisplay(xchippe)); while (mask = XtAppPending(context)) XtAppProcessEvent(context, mask); This way it doesn't block, and it processes everything including timers. Thanks for the help! > -paul asente > asente@decwrl.dec.com decwrl!asente -- It does not do to leave a dragon | Tom Weinstein ...ucbvax!hub!ucsbuxa!6600tom out of your calculations, if you | 6600tom@ucsbuxa.bitnet tom@bears.ucsb.edu live near him. --J.R.R. Tolkien | 6600tom@ucsbuxa.ucsb.edu tomw@cornu.ucsb.edu
dpb@viking.UUCP (Don Bennett 433-3311, 408) (02/16/90)
>>>> while (XtAppPending(context)) { >>>> XtAppNextEvent(context, &event); >>>> XtDispatchEvent(&event); >>>> } >> >>>> However, this seems to block when there are no events in the queue. Am >>>> I doing something wrong, or is this a bug? >> >>> Are you using timers or alternate input sources? XtAppPending returns >>> non-zero when these exist but XtAppNextEvent still blocks if there are no >>> X events. If this is the case, you might try >> >>Yes, I am using timers. >> >>> while (XtAppPending(context) & XtIMXEvent) { >>> ... >> >>Okay, but if I do this, doesn't that mean that none of my timer events >>will get processed? >> >I just figured out the right way to do this: > > XEvent event; > XtInputMask mask; > > XFlush(XtDisplay(xchippe)); > > while (mask = XtAppPending(context)) > XtAppProcessEvent(context, mask); Actually, I needed to solve a similar problem. We have a recursive version of the main loop that looks like void myMainLoop(loopTest) boolean (*looptest)(); { XEvent ev; while ((*loopTest)()) { XtNextEvent(&ev); < do some funky stuff you don't want to know about > XtDispatchEvent(&ev); } } and we were getting screwed because a timer event was setting the loop termination condition but XtNextEvent was still blocked waiting for a 'real' event. We couldn't use XtAppProcessEvent() because we needed to insert our own code between the event read and the event dispatch. The fix I used was to write a version of XtNextEvent that would either process a single timer/alternate-input event or get a real input event and return a status telling the caller which had occured. /* * myXtNextEvent - * * Return after processing one timer/alternate-input * event or after reading a single input event. * * Return true if an event was read, false otherwise. */ boolean myXtNextEvent(ev) XEvent *ev; { XtAppContext app; XtInputMask mask; app = (XtAppContext) _XtDefaultAppContext(); while (1) { mask = XtAppPending(app); if (mask & (XtIMTimer|XtIMAlternateInput)) { XtAppProcessEvent(app, (XtIMTimer|XtIMAlternateInput)); return(FALSE); } if (mask & XtIMXEvent) { /* It looks like this might process additional * alternate events if XtAppNextEvent() calls * DoOtherSources(), but I don't particularly care; */ XtAppNextEvent(app, ev); return(TRUE); } _XtwaitForSomething(FALSE, FALSE, FALSE, TRUE, NULL, app); } } /* * myMainLoop - * * recursive main loop. */ void myMainLoop(loopTest) boolean (*looptest)(); { XEvent ev; while ((*loopTest)()) if (myXtNextEvent(&ev)) { < do some funky stuff you don't want to know about > XtDispatchEvent(&ev); } } Don Bennett (408)433-3311 dpb@frame.com Frame Technology