performLayout method
Implementation
@override
void performLayout(Constraints constraints) {
final displayText =
text.isEmpty && placeholder != null ? placeholder! : text;
final desiredWidth = (displayText.length + 1).clamp(
1,
Constraints.infinity,
);
final boxConstraints = constraints.asBoxConstraints;
size = boxConstraints.constrain(Size(desiredWidth, 1));
}