// gcc `pkg-config --cflags --libs cairo` test_template.c -o test_template

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

#include <cairo.h>
#include <cairo-xlib.h>

typedef struct win {
    Display *dpy;
    int scr;

    Window win;
    GC gc;

    int width, height;
    KeyCode quit_code;
} win_t;

static void win_init(win_t *win);
static void win_deinit(win_t *win);
static void win_draw(win_t *win);
static void win_handle_events(win_t *win);

int
main(int argc, char *argv[])
{
    win_t win;

    /* do png backend */
    png_draw();

    /* do xlib backend */
    win.dpy = XOpenDisplay(0);

    if (win.dpy == NULL) {
	fprintf(stderr, "Failed to open display\n");
	return 1;
    }

    win_init(&win);

    win_draw(&win);

    win_handle_events(&win);

    win_deinit(&win);

    XCloseDisplay(win.dpy);

    return 0;
}

void
draw (cairo_t *cr, int width, int height)
{
    cairo_scale (cr, width, height);

    cairo_select_font_face (cr, "Sans", CAIRO_FONT_SLANT_NORMAL,
			    CAIRO_FONT_WEIGHT_BOLD);
    /* cairo_set_font_size (cr, 0.3); */

    cairo_move_to (cr, 0.05, 0.5);
    cairo_set_source_rgb (cr, 1, 0, 0);
    cairo_show_text (cr, "Hello");
}

int
png_draw ()
{
  int width = 400, height = 400;
  cairo_t *cr;
  cairo_surface_t *surface;

  surface = cairo_image_surface_create (CAIRO_FORMAT_ARGB32, width, height);
  cr = cairo_create (surface);

  draw (cr, width, height);

  cairo_surface_write_to_png (surface, "test.png");

  if (cairo_status (cr)) {
    printf("Cairo is unhappy: %s\n",
	   cairo_status_to_string (cairo_status (cr)));
    exit(0);
  }

  cairo_surface_destroy (surface);
  cairo_destroy (cr);

  return 0;
}

static void
win_draw(win_t *win)
{
    cairo_surface_t *surface;
    cairo_t *cr;
    Visual *visual = DefaultVisual(win->dpy, DefaultScreen (win->dpy));

    XClearWindow(win->dpy, win->win);

    surface = cairo_xlib_surface_create (win->dpy, win->win, visual,
					 win->width, win->height);
    cr = cairo_create(surface);

    draw (cr, win->width, win->height);

    if (cairo_status (cr)) {
	printf("Cairo is unhappy: %s\n",
	       cairo_status_to_string (cairo_status (cr)));
	exit(0);
    }

    cairo_destroy(cr);
    cairo_surface_destroy (surface);
}

static void
win_init(win_t *win)
{
    Window root;

    win->width = 400;
    win->height = 400;

    root = DefaultRootWindow(win->dpy);
    win->scr = DefaultScreen(win->dpy);

    win->win = XCreateSimpleWindow(win->dpy, root, 0, 0,
				   win->width, win->height, 0,
				   BlackPixel(win->dpy, win->scr), BlackPixel(win->dpy, win->scr));

    win->quit_code = XKeysymToKeycode(win->dpy, XStringToKeysym("Q"));

    XSelectInput(win->dpy, win->win,
		 KeyPressMask
		 |StructureNotifyMask
		 |ExposureMask);

    XMapWindow(win->dpy, win->win);
}

static void
win_deinit(win_t *win)
{
    XDestroyWindow(win->dpy, win->win);
}

static void
win_handle_events(win_t *win)
{
    XEvent xev;

    while (1) {
	XNextEvent(win->dpy, &xev);
	switch(xev.type) {
	case KeyPress:
	{
	    XKeyEvent *kev = &xev.xkey;

	    if (kev->keycode == win->quit_code) {
		return;
	    }
	}
	break;
	case ConfigureNotify:
	{
	    XConfigureEvent *cev = &xev.xconfigure;

	    win->width = cev->width;
	    win->height = cev->height;
	}
	break;
	case Expose:
	{
	    XExposeEvent *eev = &xev.xexpose;

	    if (eev->count == 0)
		win_draw(win);
	}
	break;
	}
    }
}