Migration guide

Subclasses that already override performResize can be migrated by simply
changing the function signature from void performResize() to
Size computeDryLayout(BoxConstraints constraints) and by returning the
calculated size instead of assigning it to the size setter. The old
implementation of performResize can be removed.

Code before migration:

@override

void

performResize

()

size

constraints

biggest

Code after migration:

// This replaces the old performResize method.

@override

Size

computeDryLayout

BoxConstraints

constraints

return

constraints

biggest