The best way is probably to add a new component to hold the inner FlexBox.
If that approach isn’t suitable for some reason, you can do your layout in multiple phases. The following should be treated as pseudocode, to illustrate the technique.
FlexBox outer;
outer.items = {
FlexItem{}.withFlex (1.0f), // a placeholder item
FlexItem{}.withMinHeight (50.0f), // another placeholder
};
outer.performLayout (getLocalBounds());
FlexBox inner;
inner.items = {
FlexItem { dialA }.withFlex (1.0f),
FlexItem { dialB }.withFlex (1.0f),
};
// Lay out this FlexBox using the bounds of a placeholder item from earlier.
// You could also use reduced() to leave space for a border drawn by a GroupComponent
inner.performLayout (outer.items[0].currentBounds);