DMA-buf textures

[nacho]

Today we are using the SoftwareRenderingContext for which on each frame we move the frame to the CPU and from the CPU back to the GPU. Ideally we would create a new RenderingContext that would use dma-buf so we can have everything in the GPU which is what GTK supports.

[bilelmoussaoui]

Note that using dmabuf would make the widget linux only. You would still need some fallback path for other platforms

[nacho]

Agreed on that

[mikkeljohnsen]

This should not use DMA-Buf, this is for cross platform embedding. :-)

Use WebkitGtk if you want DMA-Buf.

[nacho]

not really, on linux you can always use dma-buf

[kepstin]

Use WebkitGtk if you want DMA-Buf.

The point of this project is to use Servo rather than Webkit!

That said: the way WebkitGtk deals with rendering the page contents in the Gtk widget, and how it handles multi-process sandboxing might be useful to reference when working on Servo GTK. In particular, gtk/AcceleratedBackingStore.cpp could be somewhere to start looking - that has the code for handling the rendered buffer from the web content process and drawing it into the GTK window.

Note that the code is kinda hard to read since it has both GTK4 and GTK3 stuff and multiple ways of transferring textures mixed up into the same file and conditionally compiled (It looks like the GTK4 code uses GTK's built-in support for using DMA BUF textures, while the GTK3 code uses EGL extensions to manually set up the DMA BUF texture).