PtSetResources and threads

[Peng]

Hi ^^

I’m running this code from a callback attached to a button:

[code]int
draw_poly(PtWidget_t *widget, ApInfo_t *apinfo, PtCallbackinfo_t *cbinfo)
{
PhPoint_t *points;
PhPoint_t orig;
PtArg_t args[2];
int i;

/* eliminate 'unreferenced' warnings */
widget = widget, apinfo = apinfo, cbinfo = cbinfo;

// while (1) {

points = (PhPoint_t *) malloc (181 * sizeof(PhPoint_t));
for (i = 0; i < 181; i++)
{
	points[i].x = (short) (200 * cos(i * 0.01745));
	points[i].y = (short) -(200 * sin(i * 0.01745));
}
orig.x = 200;
orig.y = 0;
PtSetArg(&args[0], Pt_ARG_ORIGIN, &orig, 1);
PtSetArg(&args[1], Pt_ARG_POINTS, points, 181);
PtSetResources(ABW_RangeDisplay, 2, args);

// sleep(1); }

return(Pt_Continue);

}
[/code]

It runs pretty well and draws a nice 180° arc.
Now suppose I want to make it a thread. I turn it into a void function, remove the return(Pt_Continue), and change the callback function to call it using pthread_create. Then it still works, no problem.
Ok, now suppose I want to make it redraw every one second. I uncomment the commented lines, and then it will work once, but then crash.

My question is: why ? And how to avoid it ? (ok that’s 2 questions ^^ )[/code]

[thegman]

Put PtEnter() before your Photon function calls, and PtLeave() after them, Photon is not thread safe and those two functions block calls to Photon from other threads, making Photon calls safe to use in threads.

[Peng]

I tried this before but it didn’t work :-/
I found this in the documentation:

In response to a change to its resources, a widget may have to redisplay itself. The PtSetResources() call triggers this change. Any changes to the appearance of the widget, however, don’t take effect until control is restored to the Photon event-handling loop. Therefore, if PtSetResources() is called from within a callback function or an event-handling function, the change to the widget won’t be visible until all the callbacks in the callback list and all event handlers have been executed.

So I guess I should use a timed callback for updating the display instead of a thread…

[mezek]

If u want to use PtEnter()/PtLeave() then u would have to implement them into all threads using Photon calls. Also, as u mentioned, calling PtSetResources() doesnt actually change display, it only schedule the update on next event-handle cycle. So, after calling PtSetResources() in second thread u have to let the first thread (the one which called PtMainLoop()) to update display.

Single thread with a Timer Callback is somewhat better solution …

[Peng]

Understood !
It’s working now (with a timer)