barHeight function
Implementation
double barHeight([ VisualDensity visualDensity = const VisualDensity() ]) {
return kButtonIconSize
+ 2 * max(kButtonPadding + visualDensity.baseSizeAdjustment.dy, kDensestPadding)
+ 2 * max(kButtonMargin + visualDensity.baseSizeAdjustment.dy, kDensestButtonMargin);
}