`redraw` keeps the narrower of an old and a fresh contract so that widening
and narrowing back do not churn the parent that reads it. The drawing's half
asked whether the old range still covers this window and box before keeping
it; the answer's half did not, so a widget whose answer contract widened in
a frame that also resized the window kept a range the new window is outside.
The parent's next ask then refuses that answer and draws the whole subtree
again -- throwing away the drawing the widget had just made. Cost, not
geometry: the size kept is the size just reported.
`a_contract_this_window_is_outside_is_not_kept` draws the leaf twice before
the change and once after.
iris-ai
d8d51221ee