Allow wlr_buffer_impl.get_data_ptr to return a format. This allows the Pixman renderer to not care about get_dmabuf/get_shm, and only care about get_data_ptr. This will also help with [1], because client wl_shm buffers can't implement get_shm. [1]: https://github.com/swaywm/wlroots/pull/2892 References: https://github.com/swaywm/wlroots/issues/2864
The function has been place in an internal header for API stability reasons.