This exposes CoglTextureRectangle in the experimental cogl 2.0 api. For
now we just expose a single constructor;
cogl_texture_rectangle_new_with_size() but we can add more later.
This is part of going work to improve our texture apis with more
emphasis on providing low-level access to the varying semantics of
different texture types understood by the gpu instead of only trying to
present a lowest common denominator api.
CoglTextureRectangle is notably useful for never being restricted to
power of two sizes and for being sampled with non-normalized texture
coordinates which can be convenient for use a lookup tables in glsl due
to not needing separate uniforms for mapping normalized coordinates to
texels. Unlike CoglTexture2D though rectangle textures can't have a
mipmap and they only support the _CLAMP_TO_EDGE wrap mode.
Applications wanting to use CoglTextureRectangle should first check
cogl_has_feature (COGL_FEATURE_ID_TEXTURE_RECTANGLE).
Reviewed-by: Neil Roberts <neil@linux.intel.com>
