Wayland Work Towards State Machine For Display Control

Tiago Vignatti on Friday published initial code seeking comments regarding a state machine for display control on the Wayland Display Server.

While Wayland is nearing version 1.0, there's many items left to be addressed with this next-generation display server architecture. One of the big open items is handling of changing mode-setting and other display control settings, i.e. what RandR (the Resize and Rotate extension) is to X.Org. Tiago published some initial "RFC" code for Wayland that implements a state machine for display control.

What his state machine handles right now is backlight control and DPMS. DPMS, or Display Power Management Signalling, is what can allow the monitor to be shut-off after a period of inactivity. DPMS has been part of the VESA specification for nearly two decades.

His set of patches add about 200 lines of code to Wayland. In the end for the Wayland compositor it implements the state machine to allow moving from display on to display dim to display screensaver and then finally display off (DPMS). The state changes are based upon the time of user idleness. Right now this is being backed by just a single timer in Wayland.

Kristian Høgsberg, the founder of Wayland and fellow Intel engineer to Tiago, already responded that they've already been working on DPMS and backlight support for the Weston reference implementation, so they want to do that first. The approach they are doing with that implementation is slightly different from Vignatti's work.

For those interested in the Wayland state machine patch-set can be found on the project's mailing list.