Improve Mesa drivers recency
This is a rather vague description, because I have no idea if/how to solve it, but I've talked to @alatiera on IRC about it and we decided to discuss it here.
The problem is that GTK's rendering infrastructure has gotten more elaborate over the years and with the new renderers landing and the dmabuf work, it's at a stage where it finds bugs in Mesa. The Mesa devs have done a great job at quickly fixing all of them once they were found, but it takes a long time for those fixes to appear in Gnome Nightly, while the new GTK feature that triggers that bug is already there.
The most annoying recent example that made me investigate this issue to see if I can improve things is gtk#6321 (closed) / https://gitlab.freedesktop.org/mesa/mesa/-/issues/10434 which causes gradients on all Intel laptops to randomly be wrong. And we have a lot of gradients and a lot of nightly users with Intel laptops.
Another related thing is that with the more elaborate code, new driver features can introduce new bugs in Mesa and it would be nice if we find them before they make it into a Mesa release and all GTK apps get glitched rendering. And Mesa has a really fast pace of development.
I expect this to become more interesting if GTK switches to Vulkan by default, which we plan to try early next cycle. Vulkan drivers are a lot less exercised by other code than GL.
Of course, pulling more recent versions of Mesa might pull buggier code into Gnome Nightly and might cause nightly users too spend too much time dealing with issues in Mesa.
So I'm trying to figure out what the best way is to achieve the most recent Mesa code with the least amount of breakage.