The scaling algorithm is not specified. If we did specify a certain algorithm, we would immediate exclude half of the hardware support. Specify a simple algorithm: most hardware will probably support it, but it will not allow capable hardware to make any better even if they could. Specify a fancy algorithm: lots of hardware simply may not be able to do it. This is also Wayland core protocol, so it is not only about PCs or desktops. Therefore the exact algorithm is left as an implementation detail.
No announcement yet.
Wayland's Weston Gets Output Scaling Support