Graphics offload revisited

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Style Pass

2024-04-19 19:30:04

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.

We’ve merged new GSK renderers for GTK 4.14. The new renderers support dmabufs in the same way as the old gl renderer. In addition, the new Vulkan renderer produces dmabufs when rendering to a texture.

In GTK 4.16, the GtkGLArea widget will also provide dmabuf textures if it can, so you can put it in a GtkGraphicsOffload widget to send its output directly to the compositor.