Damage tracking

Damage tracking means that instead of re-compositing everything every frame, copying all the view output buffers around into the output framebuffer, updates are only made when something has actually changed.

Vivarium 0.0.3 automatically enables frame-wise damage tracking, where nothing is drawn unless something changes in one of the surfaces being displayed. This is an enormous improvement on the previous status quo of redrawing everything at the monitor refresh rate, and in cases where nothing is changing much (e.g. just text editors and terminals, no video) brings most of the damage tracking benefits.

Vivarium also supports full damage tracking, in which it tracks which parts of the frame have changed and only draws these. That means for example even if a video is playing at 60fps only its subregion of the screen is repeatedly redrawn. However, this full damage tracking support is a little more experimental and is not enabled by default: it should work for single outputs, and for multiple outputs if they have the same scale, but is likely to have bugs in more complex cases such as output scaling as these cases haven’t been rigorously tested.

If you’d like to enable full damage tracking, set damage-tracking-mode = "full" in the [debug] section of your config.toml.

I found quite a few internal Vivarium issues while making damage tracking work as it exercises the full stack of assumptions about how/where surfaces are displayed. There may still be more, if you see anything appearing to render incorrectly (or mostly likely not rendering at all) bug reports are gratefully received.

Wlroots 0.13

Wlroots 0.13 was released in early April but it’s taken a little while to get around to supporting it as I was focusing on damage tracking at the time. For Vivarium’s purposes there aren’t any major new features this allows, but there are plenty of background improvements.