rect method
override
Where frame index of row sits in image.
Implementation
@override
Rect rect(int row, int index) {
final resolved = _rows[row];
_checkFrame(index, resolved);
final width = _size.x;
final height = _size.y;
return .fromLTWH(
(resolved.start + index) * width,
row * height,
width,
height,
);
}