To allow for flushing of batched geometry within Cogl we can't support users
directly calling glReadPixels. glReadPixels is also awkward, not least
because it returns upside down image data.
All the unit tests have been swithed over and clutter_stage_read_pixels now
sits on top of this too.
cogl_texture_new_from_data lets you specify a source format for the users given
data, and an internal format which the user wants the GPU to see. This unit
test verifies that the users data is premultiplied, un-premultiplied or
left alone for a number of (source format, internal format) pairs.
cogl_texture_set_region allows specifying a source format, and the internal
format is determined from the texture being updated. As above we test
a number of format pairs and check Cogl is converting data correctly.
The test verifies that if the user allows COGL_FORMAT_ANY for the
internal_format then by default Cogl will choose a premultipled format for
RGBA textures.
Note: Currently this only tests cogl_texture_new_from_data and
cogl_texture_set_region, we should also test cogl_texture_new_from_file,
cogl_texture_new_from_bitmap and cogl_texture_new_from_foreign.
