Graphics offload revisited
We first introduced support for dmabufs and graphics offload last fall, and it is included in GTK 4.14. Since then, some improvements have happened, so it is time for an update.
The GStreamer 1.24 release has improved support for explicit modifiers, and the GStreamer media backend in GTK has been updated to request dmabufs from GStreamer.
Another thing that happens on the GStreamer side is that dmabufs sometimes come with padding: in that case GStreamer will give us a buffer with a viewport and expect us to only show that part of the buffer. This is sometimes necessary to accommodate stride and size requirements of hardware decoders.
GTK 4.14 supports this when offloading, and only shows the part of the dmabuf indicated by the viewport.