fn rect(backend: *Backend, rec: dimensions.Rect, rgb: dimensions.RGB) void {
    const self = @fieldParentPtr(Self, "backend", backend);
    const color = 0xFF000000 | @as(u32, rgb.r) << 16 | @as(u32, rgb.g) << 8 | rgb.b;
    var y = rec.top_left.y;
    while (y < rec.bottom_right.y) : (y += 1) {
        if (y > self.backend.height) unreachable;
        const offset = (y * backend.width);
        var x = rec.top_left.x;
        while (x < rec.bottom_right.x) : (x += 1) {
            if (x > self.backend.width) unreachable;
            //_setPixel(self, .{ .x = x, .y = y }, rgb);
            self.pixmap[offset + x] = color;
        }
    }
}