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Backend Timers

This example shows how to use backend timers.

/*****************************************************************************
 * This file is part of gfxprim library.                                     *
 *                                                                           *
 * Gfxprim is free software; you can redistribute it and/or                  *
 * modify it under the terms of the GNU Lesser General Public                *
 * License as published by the Free Software Foundation; either              *
 * version 2.1 of the License, or (at your option) any later version.        *
 *                                                                           *
 * Gfxprim is distributed in the hope that it will be useful,                *
 * but WITHOUT ANY WARRANTY; without even the implied warranty of            *
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU         *
 * Lesser General Public License for more details.                           *
 *                                                                           *
 * You should have received a copy of the GNU Lesser General Public          *
 * License along with gfxprim; if not, write to the Free Software            *
 * Foundation, Inc., 51 Franklin Street, Fifth Floor,                        *
 * Boston, MA  02110-1301  USA                                               *
 *                                                                           *
 * Copyright (C) 2009-2013 Cyril Hrubis <metan@ucw.cz>                       *
 *                                                                           *
 *****************************************************************************/

 /*

   Simple backend timers example.

  */

#include <stdio.h>
#include <GP.h>

static void redraw(GP_Backend *self)
{
        GP_Context *context = self->context;
        GP_Pixel black_pixel = GP_ColorToContextPixel(GP_COL_BLACK, context);

        GP_Fill(context, black_pixel);

        /* Update the backend screen */
        GP_BackendFlip(self);
}

static uint32_t timer_callback(GP_Timer *self)
{
        uint32_t next = random() % 10000;

        printf("Timer %s callback called, rescheduling after %u.\n",
               self->id, (unsigned) next);

        return next;
}

int main(void)
{
        GP_Backend *backend;
        const char *backend_opts = "X11:100x100";

        backend = GP_BackendInit(backend_opts, "Backend Timers Example");

        if (backend == NULL) {
                fprintf(stderr, "Failed to initialize backend\n");
                return 1;
        }

        redraw(backend);

        /*
         * Periodic timer with 1000ms interval. As the callback is set to NULL
         * Timer Event is pushed to event queue upon expiration.
         */
        GP_TIMER_DECLARE(timer1, 0, 1000, "Timer 1", NULL, NULL);

        /*
         * Timer with a callback, this timer gets scheduled depending on ouput
         * from callback (0 means disable timer).
         */
        GP_TIMER_DECLARE(timer2, 5000, 0, "Timer 2", timer_callback, NULL);

        GP_BackendAddTimer(backend, &timer1);
        GP_BackendAddTimer(backend, &timer2);

        /* Handle events */
        for (;;) {
                GP_Event ev;

                GP_BackendWaitEvent(backend, &ev);

                GP_EventDump(&ev);

                switch (ev.type) {
                case GP_EV_KEY:
                        switch (ev.val.val) {
                        case GP_KEY_ESC:
                        case GP_KEY_Q:
                                GP_BackendExit(backend);
                                return 0;
                        break;
                        }
                break;
                case GP_EV_SYS:
                        switch (ev.code) {
                        case GP_EV_SYS_RESIZE:
                                GP_BackendResizeAck(backend);
                                redraw(backend);
                        break;
                        case GP_EV_SYS_QUIT:
                                GP_BackendExit(backend);
                                return 0;
                        break;
                        }
                break;
                }
        }

        GP_BackendExit(backend);

        return 0;
}