external widget and libXt

This note documents why XEmacs external widget is important, and provides a fix to some annoying behavior on Solaris 7 when using external widget under XEmacs 21.1.14 on Solaris 7. This writeup and the patch are both courtesy of Kenny Chien (Kenny.Chien(a)morganstanley.com). Morgan Stanley's in-house C++ widget toolkit is based solely on the X11 libraries, with no dependency on Xt or Motif. This toolkit implements a Motif look and feel. The use of XEmacs's external widget feature was driven by a real business need in a trading application. In this application, users structure business logic using a high level business specific programming language. Instead of expending resources in implementing a full blown editor widget, we decided to give XEmacs external widget a try. It has been incorporated into our toolkit and used in production since 1997. The editor widget is also supported via Java on Solaris and NT. At least 3 production applications, two in C++ and one in Java, utilize this editor widget. The response from the user community has been excellent because there are simply no better editor widgets out there. Now, for the technical content. The function extw_wait_for_response() in extw-Xt.c behaves inconsistently between Solaris 2.5.1 and Solaris 7. More specifically, the underlying _XtWaitForSomething() function invoked by extw_wait_for_response() behaves differently when a timeout occurs. In Solaris 7, it doesn't seem to return -1 when it times out, it returns 1 instead. extw_wait_for_response() therefore loops indefinitely causing xemacs to hang. The fix to this problem is to not use _XtWaitForSomething(). The biggest reason is of course it is an undocumented internal Xt function, there is technically no guarantee of the existence and the behavior of this function in future releases. This patch rewrites extw_wait_for_response() to use only public Xt functions and at the same time preserve the semantics of this function. It will now behave consistently and timeout properly. Here is the patch, against XEmacs 21.1.14. extw_wait_for_response() seems to have been rewritten in XEmacs 21.4, but it still uses the undocumented _XtWaitForSomething function. This method is probably more portable... --- extw-Xt.c.save Fri May 25 17:28:57 2001 +++ extw-Xt.c Fri May 25 17:28:17 2001 ＠＠ -35,47 +35,10 ＠＠ #endif #include <X11/Intrinsic.h> -#include <X11/IntrinsicP.h> #include <stdlib.h> #include <stdio.h> #include "extw-Xt.h" -/* Yeah, that's portable! - - Why the hell didn't the Xt people just export this function - for real? */ - -#if (XT_REVISION > 5) -int _XtWaitForSomething( - XtAppContext app, - _XtBoolean ignoreEvents, - _XtBoolean ignoreTimers, - _XtBoolean ignoreInputs, - _XtBoolean ignoreSignals, - _XtBoolean block, -#ifdef XTHREADS - _XtBoolean drop_lock, -#endif - unsigned long *howlong); - -# ifndef XTHREADS -# define _XtwaitForSomething(timers,inputs,events,block,howlong,appCtx) \ - _XtWaitForSomething(appCtx,events,timers,inputs,0,block,howlong) -# else -# define _XtwaitForSomething(timers,inputs,events,block,howlong,appCtx) \ - _XtWaitForSomething(appCtx,events,timers,inputs,0,block,1,howlong) -# endif -#else -int _XtwaitForSomething( - Boolean ignoreTimers, - Boolean ignoreInputs, - Boolean ignoreEvents, - Boolean block, - unsigned long *howlong, - XtAppContext app - ); -#endif - #ifdef DEBUG_WIDGET static int geom_masks[] = { ＠＠ -195,35 +158,24 ＠＠ /* check if an event is of the sort we're looking for */ -static FILE *file; static Bool isMine(XEvent *event, QueryStruct *q) { Widget w = q->w; - fprintf(file,"Event Type is %d\n",event->type); - if (event->type == ClientMessage) - { - fprintf(file,"***** It's a ClientMessage.*****\n"); - } - + if ( (event->xany.display != XtDisplay(w)) || (event->xany.window != XtWindow(w)) ) { - if ( (event->xany.display != XtDisplay(w))) - { - fprintf(file,"Wrong Display\n"); - } - else - { - fprintf(file,"Wrong Window ID\n"); - } return FALSE; - } - if (event->xany.serial >= q->request_num) { + } + if (event->xany.serial >= q->request_num) + { if (event->type == ClientMessage && event->xclient.message_type == a_EXTW_NOTIFY && event->xclient.data.l[0] == 1 - extw_which_side && event->xclient.data.l[1] == q->type) - return TRUE; + { + return TRUE; + } } return FALSE; } ＠＠ -235,8 +187,10 ＠＠ } /* wait for a ClientMessage of the specified type from the other widget, or - time-out. isMine() determines whether an event matches. Culled from - Shell.c. */ + time-out. isMine() determines whether an event matches. + Took out the call to _XtWaitForSomething and replaced it with public + Xt api's. +*/ Bool extw_wait_for_response(Widget w, XEvent *event, unsigned long request_num, ＠＠ -247,7 +201,6 ＠＠ QueryStruct q; Bool expired; XtIntervalId id; - file=fopen("/tmp/debug","a"); q.w = w; q.request_num = request_num; ＠＠ -257,46 +210,26 ＠＠ id=XtAppAddTimeOut(app,timeout,responseTimeOut,&expired); while (!expired) { -/* fprintf(file,"Looking for Pending event.\n"); */ inputMask=XtAppPending(app); if (inputMask & XtIMXEvent) { - fprintf(file,"Got an X Event.\n"); - fflush(file); XtAppNextEvent(app,event); - if (event->type==Expose) - { - fprintf(file,"Dispatching Expose.\n"); -/* XtDispatchEvent(event); */ - } - else if (isMine(event,&q)) + if (isMine(event,&q)) { - fprintf(file,"===========> Got the Client Message Event\n"); - fflush(file); if (!expired) XtRemoveTimeOut(id); return True; } else { /* Do Nothing and go back to waiting */ - fprintf(file,"Don't want this X Event.\n"); - fflush(file); } } if (inputMask & XtIMTimer) { /* Process the expired timer */ - fprintf(file,"Got a timer event.\n"); XtAppProcessEvent(app,XtIMTimer); } - if (inputMask & XtIMAlternateInput) - { -/* fprintf(file,"Got some Alternate Input Event.\n"); */ - } } /* Must have expired */ - fprintf(file,"Timer Expired.\n"); - fflush(file); - fclose(file); return False; } -- Isaac Hollander Morgan Stanley Dean Witter isaac.hollander(a)morganstanley.com 1585 Broadway, 2nd floor (212) 761 3417 New York, NY