XWayland Lands Support For Sharing Pixmaps Via MIT-SHM

A small patch merged to X.Org Server Git enables support for MIT-SHM shared memory pixmaps with XWayland.

The patch allows for sharing pixmaps of X11 clients under XWayland via shared memory with the MIT-SHM extension.

This work was driven by the Sway/WL-ROOTS developers and they have tentative patches for making use of the functionality. Notably they are pursuing the shared memory buffers support for use in conjunction with their new Pixman software-based renderer. Simor Ser has been working on a new Pixman software renderer for WL-ROOTS with this SHM support being needed for the X11 clients.

That new renderer was merged into WL-ROOTS last month.

The WL-ROOTS Wayland compositor library is used by Sway and other compositors for doing much of the heavy lifting needed to write a modern Linux desktop Wayland compositor.