eh?.c

#include <GL/glx.h>
#include <X11/X.h>
#include <X11/Xlib-xcb.h>
#include <stddef.h>
#include <stdio.h>
#include <stdbool.h>
#include <stdlib.h>
#include <xcb/xcb.h>
#include <xcb/xfixes.h>
#define auto __auto_type

xcb_screen_t *x_screen_of_display(xcb_connection_t *c, int screen) {
	xcb_screen_iterator_t iter;

	iter = xcb_setup_roots_iterator(xcb_get_setup(c));
	for (; iter.rem; --screen, xcb_screen_next(&iter))
		if (screen == 0)
			return iter.data;

	return NULL;
}

void make_create_region_requests(xcb_connection_t *c) {
	int r = random() % 200 + 30;
	static int last_id = 0;
	for (int i = 0; i < r; i++) {
		auto region = xcb_generate_id(c);
		if (region < last_id) {
			fprintf(stderr, "id wrapped, was %#010x, now %#010x\n", last_id, region);
		}
		last_id = region;
		auto e = xcb_request_check(
		    c, xcb_xfixes_create_region_checked(c, region, 0, NULL));
		if (e) {
			fprintf(stderr,
			        "create region error, is idchoice: %d, %d\n",
			        e->error_code == XCB_ID_CHOICE,
			        e->error_code);
			abort();
		}

		// randomly keep some of the regions, so GetXIDRange won't just
		// return the whole range always.
		if (random() % 16) {
			auto e = xcb_request_check(c, xcb_xfixes_destroy_region_checked(c, region));
			if (e) {
				fprintf(stderr, "cannot destroy region");
			}
		}
	}
}

int main() {
	auto dpy = XOpenDisplay(NULL);
	auto scr = DefaultScreen(dpy);
	auto root = RootWindow(dpy, scr);
	auto c = XGetXCBConnection(dpy);
	xcb_prefetch_extension_data(c, &xcb_xfixes_id);
	xcb_xfixes_query_version(c, XCB_XFIXES_MAJOR_VERSION, XCB_XFIXES_MINOR_VERSION);

	auto scrp = x_screen_of_display(c, scr);
	auto vis = scrp->root_visual;
	XVisualInfo vreq = {.visualid = vis};
	int nitems = 0;
	auto xvis = XGetVisualInfo(dpy, VisualIDMask, &vreq, &nitems);
	auto ctx = glXCreateContext(dpy, xvis, 0, 1);
	auto pixmap = xcb_generate_id(c);
	auto e = xcb_request_check(
	    c, xcb_create_pixmap_checked(c, 24, pixmap, root, 100, 100));
	glXMakeCurrent(dpy, pixmap, ctx);
	auto fbcfg =
	    glXChooseFBConfig(dpy, scr, (const int[]){None}, &nitems);

	while (true) {
		auto glx_pixmap = glXCreatePixmap(dpy, fbcfg[0], pixmap, NULL);
		//fprintf(stderr, "A%#010x\n", glx_pixmap);
		make_create_region_requests(c);
		//fprintf(stderr, "B%#010x\n", glx_pixmap);
		glXDestroyPixmap(dpy, glx_pixmap);
		make_create_region_requests(c);
	}
}