If you use the absolutelayout and have an child that is offset from the to top (ie, y="48px"), and that child contains a component that has vflex="1", the component gets cutoff. See this example. The listbox gets cut off at the bottom at you are not able to scroll through the full list. If you change its y value to 0 from 48, then it is fine. It's like the vflex is against the parent window and not the absolute child.

<window width="300px" height="300px">
<absolutelayout hflex="1" vflex="1">
<absolutechildren x="0" y="0" hflex="1" vflex="1">
<label>Label 1</label>
</absolutechildren>
<absolutechildren x="0" y="48" vflex="1" width="200px">
<listbox hflex="1" vflex="1">
<listitem>
<listcell>
<label>Item 1</label>
</listcell>
</listitem>
<listitem>
<listcell>
<label>Item 2</label>
</listcell>
</listitem>
<listitem>
<listcell>
<label>Item 3</label>
</listcell>
</listitem>
<listitem>
<listcell>
<label>Item 4</label>
</listcell>
</listitem>
<listitem>
<listcell>
<label>Item 5</label>
</listcell>
</listitem>
<listitem>
<listcell>
<label>Item 6</label>
</listcell>
</listitem>
<listitem>
<listcell>
<label>Item 7</label>
</listcell>
</listitem>
<listitem>
<listcell>
<label>Item 8</label>
</listcell>
</listitem>
<listitem>
<listcell>
<label>Item 9</label>
</listcell>
</listitem>
<listitem>
<listcell>
<label>Item 10</label>
</listcell>
</listitem>
</listbox>
</absolutechildren>
</absolutelayout>
</window>