doyle@infonode.ingr.com (Doyle Davidson) (04/06/91)
Under X11R4 how does one design a signal handler in an
X application that needs to make X calls itself? Since Xlib
is not reentrant(?), how can one make Xlib calls in response
to a signal?
Example: Child process dies so I need to create a window with a message.
A solution that I came up with is as follows (with details removed):
main_loop()
{
while (True)
{
release_signals(...); allow signals to pass
err = select(...); Wait for server data or a signal
block_signals(...); block signals from X
while (XCheckMaskEvent(my_events)) look for any events
process_event(...); process it
}
}
The signal can only fire while I am in select (assuming indivisible
instructions) and at that point I am not inside any X calls.
Or can I get away with only blocking signals around my
"process_event()" routine?
Is there a better/more appropriate way?
I checked my out of date FAQ list and couldn't find anything.
I know this has been discussed before but I can't
find any old postings about it.
Thanks in advance,
Doyle
-------------------------------------------------------------------
Doyle C. Davidson |
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| X-clusively my own.
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-------------------------------------------------------------------evans@decvax.DEC.COM (Marc Evans) (04/08/91)
In article <1991Apr5.162131.7816@infonode.ingr.com>, doyle@infonode.ingr.com (Doyle Davidson) writes: |> Under X11R4 how does one design a signal handler in an |> X application that needs to make X calls itself? Since Xlib |> is not reentrant(?), how can one make Xlib calls in response |> to a signal? Enclosed is some code I have lying around that attempts to deal with the issue of handling signals in the X environment. It expects that you are using Xt's mainloop type of program. The callable functions are: void (*XEAppGetSignalHandler(XtAppContext app, int sig, Bool safe))() void (*XEAppSetSignalHandler(XtAppContext app, int sig, void (*pfunc)(), Bool safe, void *uptr))() Bool (*XEAppGetEventHandler(XtAppContext app, CARD32 id))() Bool (*XEAppSetEventHandler(XtAppContext app, CARD32 id, Bool (*pfunc)()))() Bool XEAppDispatchEvent(XEvent *event, void *uptr) XtInputMask XEAppPending(XtAppContext app) void XEAppWhileLoop(XtAppContext app, CARD32 *done, void *uptr) You may notice that the code also attempts to address the problem of extension events having to be dealt with in a different manner then the core events. A complete solution to these problems would likely involve far more Xt functions. The concept of the signal code is that you provide a flag indicating that when a signal arrives, the function is called immediately if safe is FALSE, or added to a list to be called once it is safe for X calls to be made if safe is TRUE. Happy hacking - Marc ========8<========8<========XESignals.c========8<========8<======== /*********************************************************** Copyright 1991 by Synergytics, 21 Hinds Lane, Pelham, New Hampshire. All Rights Reserved Permission to use, copy, modify, and distribute this software and its documentation for any purpose and without fee is hereby granted, provided that the above copyright notice appear in all copies and that both that copyright notice and this permission notice appear in supporting documentation, and that the names of Synergytics not be used in advertising or publicity pertaining to distribution of the software without specific, written prior permission. SYNERGYTICS DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL SYNERGYTICS BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. ******************************************************************/ /** The problem that is attempted to be solved below is that signal handling ** is difficult to deal with in the X environment. By hacking certain key ** functions in the Xt level we can provide a better mechanism for handling ** signals. ** ** One problem we discovered in trying to do this is that although Xlib ** provides hooks to allow it to be extended, Xt does not, and therefore ** this implementation is not safe for more then one process thread to use. ** Ideally we would like to have the ability to add an arbitrary hunk of ** memory into the XtAppContext which only we would ever manipulate, e.g. ** actions hooks are not appropriate. ** ** After some hacking it has also become apparent that Xt did not consider ** that library and server extensions would ever generate events that should ** be able to be handled above the Xt level in a transparent manner. This is ** actually rather limiting from the perspective of usability of extensions. ** We have attempted to address this as well, although again we have the ** same limitations as described above. **/ #include <stdio.h> #include <signal.h> #include <X11/extensions/bits.h> /* Comes from the XTrap sources */ #include <X11/Xmd.h> #include "IntrinsicI.h" /* The following has been lifted from NextEvent.c in X11R4 */ #ifndef NEEDS_NTPD_FIXUP # ifdef sun # define NEEDS_NTPD_FIXUP 1 # else # define NEEDS_NTPD_FIXUP 0 # endif #endif #if NEEDS_NTPD_FIXUP #define FIXUP_TIMEVAL(t) { \ while ((t).tv_usec >= 1000000) { \ (t).tv_usec -= 1000000; \ (t).tv_sec++; \ } \ while ((t).tv_usec < 0) { \ if ((t).tv_sec > 0) { \ (t).tv_usec += 1000000; \ (t).tv_sec--; \ } else { \ (t).tv_usec = 0; \ break; \ } \ }} #else #define FIXUP_TIMEVAL(t) #endif /*NEEDS_NTPD_FIXUP*/ /**** Local data structures which should be removed if Xt ever learns how to be extended in an arbitrary manner. ****/ /* signal handling */ static struct _XESignal { #ifdef __STDC__ void (*ifunc)(int,int,struct sigcontext *,void *); void (*sfunc)(int,int,struct sigcontext *,void *); #else void (*ifunc)(); void (*sfunc)(); #endif void *uptr; } _XESigArray[NSIG]; static Bool _XEWaiting = False; static Bool _XESigPending = False; static CARD8 _XESigFlags[NSIG/BitsInByte + (NSIG%BitsInByte == 0L) ? 0L : 1L]; /* event handling */ static Bool (*_XEEventFunctions[128L])(); /* The magic 128 is the maximum number * of events that could be defined in * the X environment. Unfortunately, * there doesn't appear to be a * #define for this anyplace, so we * hard code it... */ /**** Functions which are essentially Xt extensions. ****/ #ifdef __STDC__ static void _XEProcessSignals(int code, struct sigcontext *scp) #else static void _XEProcessSignals(code,scp) int code; struct sigcontext *scp; #endif { register long i; if (_XESigPending) { for (i = 0L; i < NSIG; i++) if (BitIsTrue(_XESigFlags,i)) { (*_XESigArray[i].sfunc)(i,code,scp,_XESigArray[i].uptr); BitFalse(_XESigFlags,i); } } return; } #ifdef __STDC__ static void _XEHandleSignal(int sig, int code, struct sigcontext *scp) #else static void _XEHandleSignal(sig,code,scp) int sig; int code; struct sigcontext *scp; #endif { if (sig < NSIG) { if (_XESigArray[sig].ifunc) { (*_XESigArray[sig].ifunc)(sig,code,scp,_XESigArray[sig].uptr); } else if (_XESigArray[sig].sfunc) { if (! _XEWaiting) { _XESigPending = True; BitTrue(_XESigFlags,sig); } else { _XESigPending = True; BitTrue(_XESigFlags,sig); _XEProcessSignals(code,scp); } } } } #ifdef __STDC__ void (*XEAppGetSignalHandler(XtAppContext app, int sig, Bool safe))() #else void (*XEAppGetSignalHandler(app, sig, safe))() XtAppContext app; int sig; Bool safe; #endif { return((sig < NSIG) ? (safe ? _XESigArray[sig].sfunc : _XESigArray[sig].ifunc) : NULL); } #ifdef __STDC__ void (*XEAppSetSignalHandler(XtAppContext app, int sig, void (*pfunc)(), Bool safe, void *uptr))() #else void (*XEAppSetSignalHandler(app, sig, pfunc, safe, uptr))() XtAppContext app; int sig; void (*pfunc)(); Bool safe; void *uptr; #endif { void (*rfunc)() = XEAppGetSignalHandler(app,sig,safe); if (sig < NSIG) { if (safe) { _XESigArray[sig].sfunc = pfunc; } else { _XESigArray[sig].ifunc = pfunc; } _XESigArray[sig].uptr = uptr; (void)signal(sig,(void *)_XEHandleSignal); } return(rfunc); } #ifdef __STDC__ Bool (*XEAppGetEventHandler(XtAppContext app, CARD32 id))() #else Bool (*XEAppGetEventHandler(app, id))() XtAppContext app; CARD32 id; #endif { return(id < sizeof(_XEEventFunctions) ? _XEEventFunctions[id] : NULL); } #ifdef __STDC__ Bool (*XEAppSetEventHandler(XtAppContext app, CARD32 id, Bool (*pfunc)()))() #else Bool (*XEAppSetEventHandler(app,id,pfunc))() XtAppContext app; CARD32 id; Bool (*pfunc)(); #endif { Bool (*rfunc)() = XEAppGetEventHandler(app,id); if (id < sizeof(_XEEventFunctions)) { _XEEventFunctions[id] = pfunc; } return(rfunc); } #ifdef __STDC__ Bool XEAppDispatchEvent(XEvent *event, void *uptr) #else Bool XEAppDispatchEvent(event,uptr) XEvent *event; void *uptr; #endif { Bool status = False; CARD32 id = event->type; /* If the event is one of the extension events, handle it specially, * otherwise, pass it off to Xt for processing. */ if (id < sizeof(_XEEventFunctions) && _XEEventFunctions[id]) { status = (*_XEEventFunctions[id])(event,uptr); } else { status = XtDispatchEvent(event); } return(status); } #ifdef __STDC__ XtInputMask XEAppPending(XtAppContext app) #else XtInputMask XEAppPending(app) XtAppContext app; #endif { TimerEventRec *te_ptr; struct timeval cur_time; struct timezone cur_zone; XtInputMask retmask = XtAppPending(app) & ~(XtIMTimer | XtIMAlternateInput); /* Test for timer */ for (te_ptr = app->timerQueue; te_ptr != NULL; te_ptr = te_ptr->te_next) { (void)gettimeofday(&cur_time, &cur_zone); FIXUP_TIMEVAL(cur_time); if (IS_AFTER(te_ptr->te_timer_value, cur_time)) { /* This timer is due to fire */ retmask |= XtIMTimer; break; } } /* Test for alternate input */ if (app->outstandingQueue != NULL) { retmask |= XtIMAlternateInput; } return(retmask); } #ifdef __STDC__ void XEAppWhileLoop(XtAppContext app, CARD32 *done, void *uptr) #else void XEAppWhileLoop(app,flags,uptr) XtAppContext app; CARD32 *done; void *uptr; #endif { XEvent event; XtInputMask imask; int status = True; for (_XEWaiting = False; !(*done);) { imask = XEAppPending(app); /* The point of this if statement is to prevent NextEvent and * ProcessEvent from blocking extension events from being * processed. */ if (imask & XtIMXEvent) { (void)XtAppNextEvent(app,&event); (void)XEAppDispatchEvent(&event,uptr); } else if (imask & (XtIMTimer | XtIMAlternateInput)) { XtAppProcessEvent(app,(XtIMTimer | XtIMAlternateInput)); } else { _XEWaiting = True; _XtwaitForSomething(False, False, False, True, 0L, app); _XEWaiting = False; } /* If there are safe signal handlers waiting to be run, do them now */ if (_XESigPending) { _XEProcessSignals(0L,NULL); } } return; } ========8<========8<========bits.h========8<========8<======== /* * This include file is designed to be a portable way for systems to define * bit field manipulation of arrays of bits. */ #ifndef __BITS__ #define __BITS__ "@(#)bits.h 1.6 - 90/09/18 " /* RCSID = $Header$" */ /***************************************************************************** Copyright 1987, 1988, 1989, 1990 by Digital Equipment Corporation, Maynard, MA Permission to use, copy, modify, and distribute this software and its documentation for any purpose and without fee is hereby granted, provided that the above copyright notice appear in all copies and that both that copyright notice and this permission notice appear in supporting documentation, and that the name of Digital not be used in advertising or publicity pertaining to distribution of the software without specific, written prior permission. DIGITAL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL DIGITAL BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. *****************************************************************************/ /* * * CONTRIBUTORS: * * Dick Annicchiarico * Robert Chesler * Dan Coutu * Gene Durso * Marc Evans * Alan Jamison * Mark Henry * Ken Miller * */ typedef unsigned char *UByteP; /* Pointer to an unsigned byte array */ #define BitsInByte 8L /* The number of bits in a byte */ #define BitInByte(bit) /* Returns the bit mask of a byte */ \ (1L << (((bit) % BitsInByte))) #define BitInWord(bit) /* Returns the bit mask of a word */ \ (1L << (((bit) % (BitsInByte * 2L)))) #define BitInLong(bit) /* Returns the bit mask of a long */ \ (1L << (((bit) % (BitsInByte * 4L)))) #define ByteInArray(array,bit) /* Returns the byte offset to get to a bit */ \ (((UByteP)(array))[(bit) / BitsInByte]) #define BitIsTrue(array,bit) /* Test to see if a specific bit is True */ \ (ByteInArray(array,bit) & BitInByte(bit)) #define BitIsFalse(array,bit) /* Test to see if a specific bit is False */ \ (!(BitIsTrue(array,bit))) #define BitTrue(array,bit) /* Set a specific bit to be True */ \ (ByteInArray(array,bit) |= BitInByte(bit)) #define BitFalse(array,bit) /* Set a specific bit to be False */ \ (ByteInArray(array,bit) &= ~BitInByte(bit)) #define BitToggle(array,bit) /* Toggle a specific bit */ \ (ByteInArray(array,bit) ^= BitInByte(bit)) #define BitCopy(dest,src,bit) /* Copy a specific bit */ \ BitIsTrue((src),(bit)) ? BitTrue((dest),(bit)) : BitFalse((dest),(bit)) #define BitValue(array,bit) /* Return True or False depending on bit */ \ (BitIsTrue((array),(bit)) ? True : False) #define BitSet(array,bit,value) /* Set bit to given value in array */ \ (value) ? BitTrue((array),(bit)) : BitFalse((array),(bit)) #endif /* __BITS__ */ -- =========================================================================== Marc Evans - WB1GRH - evans@decvax.DEC.COM | Synergytics (603)635-8876 Unix and X Software Consultant | 21 Hinds Ln, Pelham, NH 03076 ===========================================================================