When x or y are >= the width or height of the render target, then the width or height of the scissor/viewport rect is zero, no further logic is needed. This is different from the case of x or y being negative, because then there is still a chance that there is an in-bounds area (if width or height are large enough). It is important to make this check based on the original value of x and y, not the clamped ones. Otherwise we end up with a 1 pixel wide region even when the expected result is a width or height of 0. Previously the incorrect subtraction of 1 in the final clamping of w and h masked this, but once that is fixed, the issue fixed here becomes visible in the cubemap_scissor manual test. Change-Id: I3d4b0a163a16aa1116b1e838fa95c0faf7b56a3d Reviewed-by: Eirik Aavitsland <eirik.aavitsland@qt.io>