Hi, since Mame 0.218, when applying a GLSL filter that implement a curvature effect, the black background behind the rounded edges are filled with an extension of the game viewport, so it is like no curvature effect had been applied at all (although following scanlines you can realice that it is infact applied).
I attach the glsl lottes shader, together with my mame.ini (default one just with the glsl enabled), and two screenshot taken from Mame 0.217 and Mame 0.218
PS: I also tested before Mame 0.217,and it works ok, and from Mame 0.218 up to Mame 0.225 and it fails.
Thanks and regards.