computeHeaderExtent method
Implementation
double computeHeaderExtent() {
if (_headerSize != null) {
return switch (constraints.axis) {
Axis.vertical => _headerSize!.height,
Axis.horizontal => _headerSize!.width,
};
} else {
assert(headerChild.hasSize);
return switch (constraints.axis) {
Axis.vertical => headerChild.size.height,
Axis.horizontal => headerChild.size.width,
};
}
}