inset method
Implementation
Rect inset({int top = 0, int right = 0, int bottom = 0, int left = 0}) {
final w = width - left - right;
final h = height - top - bottom;
if (w <= 0 || h <= 0) return Rect(x + left, y + top, 0, 0);
return Rect(x + left, y + top, w, h);
}