canvas reflows when the GUI pane is opened/closed
canvas reflows when the GUI pane is opened/closed

Before, when the GUI pane was fully opened,
the canvas would not reflow and move up.

This made it look odd, because the whitespace above and below was
left uneven.

Now when the GUI pane opens and closes, it does reflow, correcting
this issue.

star090807/SkyBrush,star090807/SkyBrush