expandToFit method
Copy this, expanding to fit. Throws exception if world is already too big to fit.
Implementation
GridWorld expandToFit(int width, int height) {
if (_numCols > width) {
throw ArgumentError('world too wide ($_numCols) to expand into $width');
}
if (_numRows > height) {
throw ArgumentError('world too tall ($_numRows) to expand into $height');
}
final padW = _padding(width, _numCols);
final padH = _padding(height, _numRows);
return padLeft(padW.item1)
.padRight(padW.item2)
.padTop(padH.item1)
.padBottom(padH.item2);
}