Eliminate corner extents and instead use cursor position to map SSD
borders and extents to corner contexts, with a size configurable by the
<resize><cornerRange> parameter. This simplifies extent handling,
eliminates bugs in the detection of corner context, and allows users to
expand corner targets if they wish.
Co-authored-by: Andrew J. Hesford <ajh@sideband.org>
This fixes the ugly look of SSD for tiny windows (e.g. "xterm -geometry
1x1") due to the early return in `ssd_update_geometry()`. Now SSDs are
rendered correctly for those windows by hiding some buttons when the
window width is smaller than the total width of buttons. Additionally for
windows smaller than (button width)*2, the corners are un-rounded so a
small titlebar can be rendered with a scene-rect.
