OpenGL uses the diamond exit rule to rasterize lines. If we don't shift
the points down and to the right by 0.5, the line can sometimes miss a
pixel when it shouldn't. The final fragment of a line isn't drawn. By
drawing the lines clockwise, we can avoid a missing pixel in the rectangle.
See section 3.4.1 in the OpenGL 1.5 specification.
Fixes#32279
bdaedb601c