Previously, we would get a line of junk pixels to the right or bottom of
the captured bitmap.
Two aspects to this:
- Use Painter's clip-rect functionality instead of trying to implement
it ourselves.
- Switch from ScalingMode::NearestFractional to ::NearestNeighbor.
Somehow, `draw_scaled_bitmap(NearestFractional)` draws outside of the
Painter's clip-rect. I can't discern any difference in behavior
between these two otherwise.
We also now use the same bitmap for drawing the grid as we used for the
bitmap, since this had issues where it wasn't drawn to the edge of the
bitmap.
7cc118e84e