QRectF::contains includes all edges. If two subsurfaces are next to each
other ::contains will treat it as having a singularity where a value is
on 2 subsurfaces rather than either one of the other, which isn't what
we want for our purposes.

The unit test is extended but also featured some wrong values, the
biggest clue that it was wrong was that we used different test
co-ordiantes for surfaceContains and inputContains.