Minimal XCB + Cairo example in Zig

xcb.zig

const c = @cImport({
    @cInclude("xcb/xcb.h");
    @cInclude("cairo/cairo-xcb.h");
    @cInclude("cairo/cairo.h");
});
const std = @import("std");

pub fn lookup_visual(s: *c.xcb_screen_t, visual: c.xcb_visualid_t) ?*c.xcb_visualtype_t {
    var d = c.xcb_screen_allowed_depths_iterator(s);
    while (d.rem != 0) {
        var v = c.xcb_depth_visuals_iterator(d.data);
        while (v.rem != 0) {
            if (@ptrCast(*c.xcb_visualtype_t, v.data).visual_id == visual) {
                return v.data;
            }
            c.xcb_visualtype_next(&v);
        }
        c.xcb_depth_next(&d);
    }
    return null;
}

pub fn main() void {
    std.debug.warn("Starting...\n");
    var data: ?[*]const u8 = null;
    var scr: ?[*]c_int = null;
    const conn = c.xcb_connect(data, scr);
    defer c.xcb_disconnect(conn);

    // need to cast from unknown length pointer to single pointer
    const s = @ptrCast(*c.xcb_screen_t, c.xcb_setup_roots_iterator(c.xcb_get_setup(conn)).data);

    const window = c.xcb_generate_id(conn);

    const win_class: u16 = @enumToInt(c.XCB_WINDOW_CLASS_INPUT_OUTPUT);

    // TODO handle cookies
    _ = c.xcb_create_window(conn, c.XCB_COPY_FROM_PARENT, window, s.root, 0, 0, 150, 150, 0, win_class, s.root_visual, 0, null);

    _ = c.xcb_map_window(conn, window);

    _ = c.xcb_flush(conn);

    const vis = lookup_visual(s, s.root_visual);
    var surf = c.cairo_xcb_surface_create(conn, window, vis, 150, 150);
    if (surf == null) return;

    var ctx = c.cairo_create(surf);
    _ = c.xcb_flush(conn);

    var toggle: bool = true;
    while (true) {
        if (toggle) {
            c.cairo_set_source_rgb(ctx, 1, 1, 1);
        } else {
            c.cairo_set_source_rgb(ctx, 0, 0, 0);
        }
        toggle = !toggle;
        c.cairo_paint(ctx);
        c.cairo_surface_flush(surf);
        _ = c.xcb_flush(conn);
        std.os.time.sleep(1e9);
    }
}