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Status update, September 2022

Hi all!

This month I’ve been working on stuff I’d usually not work on willingly. And by that I mean Rust and screen tearing of course.

I’ve been randomly typing keys on my keyboard and before I knew it, a wlroots-rs repository was created. Everybody is saying how difficult (or even impossible) it is to write Rust bindings for wlroots so I wanted to see for myself and give it a try. One thing is clear: these people weren’t wrong. The first step was to wire up bindgen to automatically generate Rust declarations from the wlroots headers, and that was easy enough. Then I needed to figure out how to use libwayland’s intrusive linked lists (wl_list, wl_signal and wl_listener) from Rust. I took a while to build a basic example where a fixed wl_signal is listened to. Then it took more time to figure out a (hacky) way to abstract that into a re-usable helper. And now I’m stuck at trying to figure out a reasonable Rust API.

The main issue is that Rust lifetime concepts don’t map well to wlroots/Wayland. I’ve taken some inspiration from Smithay and introduced a BackendHandler trait which can be implemented by a compositor, and which has its methods called when a wlroots signal is emitted. This works nicely for simple cases, but sometimes signals are used to introduce new objects to the compositor (e.g. wlr_backend.events.new_output). Sometimes signals reference an existing object. If the compositor owns all wlroots objects, then wlroots can’t fire a signal referencing these objects. Also, the compositor would like to listen to signals on objects created by wlroots, e.g. wlr_output.events.destroy. My next try will maybe introduce some kind of wlroots object handle (and there can be multiple handles referencing the same wlroots object), but not sure how it’ll turn out. If you have any good ideas, please share! My latest work is sitting in the handler-v2 branch.

In other graphics news, I’ve been working on adding screen tearing support to the kernel and Wayland. In the past I’ve been pretty averse to screen tearing, because I personally find it very undesirable. But I’ve come to understand that it can be viewed as a user preference, and some people want to turn it on when playing a game. After seeing some people ask about it in #wayland, and seeing that Valve wants it too, I’ve decided to bite the bullet and implement the missing pieces. To be clear, tearing will be opt-in, only used when explicitly enabled by the user.

There are two missing pieces. The first one is in the kernel uAPI: user-space has no way to perform tearing page-flips with the atomic uAPI. I’ve sent patches to address this. The second missing piece is in the Wayland protocol: Vulkan apps have a way to request tearing via VK_PRESENT_MODE_IMMEDIATE_KHR, but Mesa doesn’t have a way to communicate this preference to the Wayland compositor. Xaver Hugl has been working on a protocol extension for this, and I’ve been working on a Mesa implementation.

Work on libdisplay-info is continuing slowly. The EDID format is really trying very hard to be as annoying to parse as possible, but it makes for a good project to work on when I don’t want to think too much. I’ve started adding DisplayID support, which is the more modern standard for display device metadata. I’ve experimented a bit with Emscripten and wrote a web version of the tool.

As a freedesktop.org sysadmin, I’ve migrated our secondary nameservers. We were using SPI’s nameservers but these are getting decommissioned, so I’ve switched to Gandi’s. I’ve also investigated issues with our SMTP server: spammers were issuing a lot of subscription requests, so our outgoing queue was full and mail providers were starting to reject our emails. I had to ban the spammers and purge the bad emails from our queue.

I’ve made some good progress on IRC software. If you haven’t read it already, I’ve written a blog post about ongoing work on OAuth integration with IRC. Goguma finally gained support for the /me command and better handles sending long messages. I’ve released a new bugfix version of soju, with various stability improvements around stuck WHO responses and Web Push. I’ve also fixed a bug in OFTC’s server which was causing some issues with soju and Goguma.

That’s it for now, see you next month!


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