Signed-off-by: Matteo Bruni mbruni@codeweavers.com --- Avoids two failures in (upcoming) d3d11:test_viewport().
My understanding of what's happening is: the affected quad extends to the left of the viewport bounds and moving the viewport even a tiny bit to the left makes GL take an extra column of pixels in consideration. Those pixels are covered by the quad since the pixel center is inside the quad, so they are drawn.
My reading of the spec doesn't entirely clarify if this is correct / expected behavior, of course the pixel center of those "extra" pixels isn't inside the viewport, but part of the pixel is. It looks to me as the first few lines at https://docs.microsoft.com/en-us/windows/desktop/direct3d11/d3d10-graphics-p... might be interpreted as implying this is actually correct behavior as far as d3d is concerned and I suspect the hardware to be quite tied to it.
FWIW decreasing the offset fixes the issue only when the offset is effectively set to 0.
Of course the offset was added in the first place for a reason, specifically to force the expected (d3d) top-left rule for triangle rasterization, since OpenGL leaves that unspecified except for requiring that only one of two adjacent triangles get to cover any pixel. I suspect that all the GPUs supporting ARB_clip_control also in practice make use of the same rule in OpenGL. Also the test should check that case too and it passes for me on AMD and Nvidia.
If this all seems too much of a hassle I can drop this patch and update the test accordingly, no worries. I really only wanted to get to the bottom of the test failure, this patch created itself while debugging :P
dlls/wined3d/state.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/dlls/wined3d/state.c b/dlls/wined3d/state.c index 1b5eacdf216..43fef746f11 100644 --- a/dlls/wined3d/state.c +++ b/dlls/wined3d/state.c @@ -4089,7 +4089,7 @@ static void viewport_miscpart_cc(struct wined3d_context *context, { /* See get_projection_matrix() in utils.c for a discussion about those values. */ float pixel_center_offset = context->d3d_info->wined3d_creation_flags - & WINED3D_PIXEL_CENTER_INTEGER ? 63.0f / 128.0f : -1.0f / 128.0f; + & WINED3D_PIXEL_CENTER_INTEGER ? 63.0f / 128.0f : 0.0f; const struct wined3d_gl_info *gl_info = context->gl_info; struct wined3d_viewport vp[WINED3D_MAX_VIEWPORTS]; GLdouble depth_ranges[2 * WINED3D_MAX_VIEWPORTS];