You could create a component (extending UIComponent) called
"Line" and override the updateDisplayList function, drawing the
actual line there. Then place this component where you want the
line drawn and add a resize handler to the outer component. When
the outer component is resized, calculate a new scaleX and scaleY
to the Line component; this way you won't have to redraw the line.
I think its easier to just redraw the line in by overriding
the updateDisplayList function in the component where you want the
May be someone else will think of a better solution.