gistfile1.txt

#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/time.h>
#include <unistd.h>
#include <cairo-gl.h>

#ifndef M_PI
#define M_PI (3.14159265)
#endif

static EGLint eglDpyAttrs[] = {
    EGL_RED_SIZE,        8,
    EGL_GREEN_SIZE,      8,
    EGL_BLUE_SIZE,       8,
    EGL_DEPTH_SIZE,      24,
    EGL_STENCIL_SIZE,    8,
    EGL_RENDERABLE_TYPE, EGL_OPENGL_BIT,
    EGL_NONE
};

static const EGLint eglCtxAttrs[] = {
    EGL_CONTEXT_CLIENT_VERSION, 2,
    EGL_NONE
};

const int gWidth = 500;
const int gHeight = 500;

int main(int argc, char *argv[]) {
    EGLDisplay display;
    EGLint nConfigs;
    EGLConfig config;
    EGLSurface surface;
    EGLContext context;

    cairo_device_t* cd;
    cairo_surface_t* cs;
    cairo_t *cr;

    Display *xDpy;
    Window window;

    double angle;
    struct timeval start, now;

    xDpy = XOpenDisplay(NULL);
    window = XCreateSimpleWindow(xDpy, XDefaultRootWindow(xDpy), 0, 0, gWidth, gHeight, 0, 0, 0);
    XMapWindow(xDpy, window);
    display = eglGetDisplay(xDpy);

    eglInitialize(display, NULL, NULL);
    eglChooseConfig(display, eglDpyAttrs, &config, 1, &nConfigs);

    eglBindAPI(EGL_OPENGL_ES_API);
    context = eglCreateContext(display, config, NULL, eglCtxAttrs);
    cd = cairo_egl_device_create(display, context);

    surface = eglCreateWindowSurface(display, config, window, 0);
    cs = cairo_gl_surface_create_for_egl(cd, surface, gWidth, gHeight);

    gettimeofday(&start, NULL);

    for(;;) {
        cr = cairo_create(cs);

        gettimeofday(&now, NULL);
        angle = (now.tv_sec - start.tv_usec + (now.tv_usec-start.tv_usec)*1e-6) * M_PI/2;

        cairo_set_source_rgba(cr, 1., 1., 1., 1.);
        cairo_paint(cr);

        cairo_set_source_rgba(cr, 0., 0., 0., 1.);
        cairo_set_line_width (cr, 10.);
        cairo_arc (cr, gWidth/2., gHeight/2., 100., angle, angle + M_PI/4);
        cairo_stroke (cr);

        cairo_destroy(cr);

        cairo_gl_surface_swapbuffers(cs);
    }

    return 0;
}