A low-level #CoglTexture making up part of a #CoglMetaTexture.
A float 4-tuple ordered like (tx1,ty1,tx2,ty2) defining what region of the current sub_texture maps to a sub-region of a #CoglMetaTexture. (tx1,ty1) is the top-left sub-region coordinate and (tx2,ty2) is the bottom-right. These are low-level texture coordinates.
A float 4-tuple ordered like (tx1,ty1,tx2,ty2) defining what sub-region of a #CoglMetaTexture this low-level sub_texture maps too. (tx1,ty1) is the top-left sub-region coordinate and (tx2,ty2) is the bottom-right. These are high-level meta-texture coordinates.
A callback used with cogl_meta_texture_foreach_in_region() to retrieve details of all the low-level #CoglTextures that make up a given #CoglMetaTexture.