Sets the horizontal alignment, from 0 (start) to 1 (end).
This affects the children allocation during transitions, when they exceed the size of the hugger.
For example, 0.5 means the child will be centered, 0 means it will keep the start side aligned and overflow the end side, and 1 means the opposite.
| this |
a hugger |
| xalign |
the new alignment value |