Horde3D

I don't know, if calcTextureSize is just used for memory statistics, which need not (and cannot) be too accurate but I think the computation for the DXT compressed sizes should replace

with

as I think the DXT formats should round up, to not loose information. If it is loaded from file it should always fit, but perhaps Horde3D sometime in the future supports compression on the fly (which OpenGL imo does when using glTexImage2D on compressed textures).

Which case exactly do you think might be problematic? NPOT textures that are not a multiple of 4 in either dimension?

Yes, that's what I mean. This only happens, when you load an uncompressed image into a compressed texture, which is not supported by Horde at the moment, I think.