disable_bindless.zig

const needle: []const u8 = "layout(bindless_sampler)";
const needle_len: usize = needle.len;

pub fn disableBindless(
    bytes: []u8,
    locations: []const usize,
) ![]u8 {
    var buf: [50]u8 = undefined;
    var loc: usize = 0;

    var i: usize = 0;
    var line_num: usize = 0;
    while (i < bytes.len) {
        if (loc >= locations.len) break;
        if (bytes[i] != '\n') {
            i += 1;
            continue;
        }
        line_num += 1;
        const line_start = i + 1;
        var j: usize = line_start + 1;
        while (j < bytes.len) {
            if (loc >= locations.len) break;
            if (bytes[j] != '\n') {
                j += 1;
                continue;
            }
            if (line_num == 1) {
                // comment out extension header
                bytes[line_start] = '/';
                bytes[line_start + 1] = '/';
            }
            if (line_start + needle_len > bytes.len) break;
            const line = bytes[line_start..j];
            var zeroed = " " ** needle_len;
            var replacement_buf: [needle_len]u8 = undefined;
            @memcpy(&replacement_buf, zeroed[0..]);
            if (line.len < needle_len) break;
            if (!std.mem.eql(u8, line[0..needle_len], needle)) break;
            const replacement = try std.fmt.bufPrint(
                &buf,
                "layout(binding={d})",
                .{locations[loc]},
            );
            @memcpy(replacement_buf[0..replacement.len], replacement[0..replacement.len]);
            @memcpy(bytes[line_start .. line_start + needle_len], replacement_buf[0..]);
            loc += 1;
            j += 1;
            break;
        }
        i += 1;
    }
    return bytes;
}

scene.zig

    self.earth_normal_map = rhi.Texture.init(self.ctx.args.disable_bindless) catch null;
    self.earth_normal_map.?.texture_unit = 2;
    self.earth_texture = rhi.Texture.init(self.ctx.args.disable_bindless) catch null;
    self.earth_texture.?.texture_unit = 3;
    self.earth_height_map = rhi.Texture.init(self.ctx.args.disable_bindless) catch null;
    self.earth_height_map.?.texture_unit = 16;
    const disable_bindless = rhi.Texture.disableBindless(self.ctx.args.disable_bindless);
    const frag_bindings = [_]usize{ 0, 1, 2, 3, 16 };
    const vert_bindings = [_]usize{16};
    {
        var s: rhi.Shader = .{
            .program = prog,
            .instance_data = true,
            .frag_body = if (!disable_bindless) frag else rhi.Shader.disableBindless(
                frag,
                frag_bindings[0..],
            ) catch @panic("bindless"),
            .bindless_vertex = !disable_bindless,
            .fragment_shader = .disabled,
        };
        s.attach(self.allocator, rhi.Shader.single_vertex(
            if (!disable_bindless) vert else rhi.Shader.disableBindless(vert, vert_bindings[0..]) catch @panic("bindless"),
        )[0..]);
    }