debugPaintSizeEnabled top-level property
Causes each RenderBox to paint a box around its bounds, and some extra boxes, such as RenderPadding, to draw construction lines.
The edges of the boxes are painted as a one-pixel-thick
const Color(0xFF00FFFF) outline.
Spacing is painted as a solid
const Color(0x90909090) area.
Padding is filled in solid
const Color(0x900090FF), with the inner edge
const Color(0xFF0090FF), using debugPaintPadding.
bool debugPaintSizeEnabled = false