Hi dbl,

Thanks for your prompt reply. Here is the complete source code

-----------------------------------------------------------
static Widget top_level;
static XtAppContext app_context;
static Widget tree;

int main(int argc, char **argv)
{
Widget main_window, main_form;

XtSetLanguageProc(NULL, NULL, NULL);

top_level = XtVaAppInitialize(&app_context, "MyTreeProgram",
NULL, 0, &argc, argv,
NULL, NULL);
main_window = XtVaCreateManagedWidget("main_window",
xmMainWindowWidgetClass, top_level,
NULL);
main_form = XtVaCreateManagedWidget("main_form",
xmFormWidgetClass, main_window,
NULL);
tree = XtVaCreateWidget("tree",
xmContainerWidgetClass, main_form,
XmNlayoutType, XmOUTLINE,
XmNautomaticSelection, XmAUTO_SELECT,
XmNentryViewType, XmSMALL_ICON,
NULL);

/* Create tree nodes */
populate_tree();

XtAppAddTimeOut(app_context, 2000,
(XtTimerCallbackProc)timer_cb, NULL);

XtManageChild(tree);
XtManageChild(main_form);

XtRealizeWidget(top_level);
XtAppMainLoop(app_context);
}

static void timer_cb(XtPointer client_data, XtIntervalId *timer)
{
time_t now = time(NULL);
char str[64];

cftime(str, "%T", &now);
printf("timer_cb %s
", str);
XtAppAddTimeOut(app_context, 2000,
(XtTimerCallbackProc)timer_cb, NULL);
}

static void populate_tree() {
int i, j, k;
char node_name[128];
Widget level1, level2, level3;

for(i=0; i<2; i++) {
sprintf(node_name, "Node_%d", i+1);
level1 = XtVaCreateManagedWidget(node_name,
xmIconGadgetClass, tree,
XmNoutlineState, XmEXPANDED,
XmNshadowThickness, 0,
NULL);

for(j=0; j<2; j++) {
sprintf(node_name, "Node_%d_%d", j+1, i+1);
level2 = XtVaCreateManagedWidget(node_name,
xmIconGadgetClass, tree,
XmNentryParent, level1,
XmNoutlineState, XmEXPANDED,
XmNshadowThickness, 0,
NULL);

for(k=0; k<3; k++) {
sprintf(node_name, "Node_%d_%d_%d",
k+1, j+1, i+1);
level3 = XtVaCreateManagedWidget(node_name,
xmIconGadgetClass, tree,
XmNentryParent, level2,
XmNshadowThickness, 0,
NULL);
}
}
}
}
-----------------------------------------------------------

As you can see, I`m not doing any thing special there.
I haven`t used any debugger.
I looked at the XmContainer.c in openmotif 2.1.30, and I found that a timer is used to detect double clicks and things like that. Could this be interfering with my timer??
Also, what happens when a timer expires while the application is busy processing events, e.g. timer expires at t=1 sec. and
application is busy between t=0 and 2 sec.? Does it just ignore the timer event or delay its processing until it`s free? I assume it delays the processing, but it appears to me that this is not what is happening here.

I appreciate your feedback and thanks for your time.

inas

Hi dbl,

I assume

> Only if XmContainer is *processing* events -- and discarding
> timers -- should the timers fail to fire.

means that it is possible that my timer fails to fire, and thus I can`t count on it to always be there (since it reschedules itself in the timer callback).

I tried to use setitimer() to produce SIGALRM periodically and install a signal handler for it, i.e.

-------------------------------------------------------
main()
{
struct itimerval itimer_val;

setitimer(ITIMER_REAL, &itimer_val, NULL);
sigset(SIGALRM, sig_handler);
sig_id = XtAppAddSignal(app_context, safe_signal_handler, NULL);
}

void sig_handler(int unused)
{
XtNoticeSignal(sig_id);
}

void safe_signal_handler(XtPointer client_data, XtSignalId *Id)
{
timer_id = XtAppAddTimeOut(app_context, 0,
(XtTimerCallbackProc)timer_cb, NULL);
}
-------------------------------------------------------

I modified one of the examples in Motif Programming Manual Vol. 6A by A. Fountain, to come up with the above code.
It seems to work fine. I was wondering if you know of any potential problems with handling UNIX signals in the above manner.

Thanks again for your help.