Redshift: Disable smooth day and night transition in the config file not working

[6arms1leg]

The example configuration file on the Redshift website reads:

; Enable/Disable a smooth transition between day and night
; 0 will cause a direct change from day to night screen temperature.
; 1 will gradually increase or decrease the screen temperature.
transition=1

There seems to be a bug in Redshift that causes the transition option in the configuration file to not work as described: Instead of handling the transition between day and night it only changes the transition between application start-up and shutdown (and delay the latter as a consequence).
So transition=0 does not cause a direct change from day to night screen temperature.

This issue was observed on Gentoo and Arch Linux with the latest Redshift release.

Many thanks for this great program!

[tifv]

I would rather say, all the options work perfect, but the documentation is incomplete. The documentation should be more explicit about what transition is controlled by what option:

• startup/shutdown transition is controlled by transition config option (and -r command line option);
• day/night transition is controlled by elevation-high and elevation-low config options.

If this is the case, mentioned example configutaion on Redshift website is just wrong and should be corrected.

[msjyoo]

@tifv How can those two options be used?

[tifv]

@sekjun9878 I use transition=0 in redshift.conf to disable transition on startup.
I experimented with elevation-high and elevation-low to disable day/night transition (specifically, I recall that I had set both values to 0.0, so that transition period collapsed and transition between day and night became instant).

[tifv]

@sekjun9878 man redshift may be a bit short on description of these options. More elaborate description may be as follows (there is a bit of my guesswork):

• transition=1 enables transition on startup/shutdown (default)
• transition=0 disables transition on startup/shutdown.
• elevation-high means minimal angle of sun above horizon to be considered «100% day» (default is 3.0, I believe, degrees).
• elevation-low means maximal angle of sun above horizon to be considered «100% night» (default is -6.0; negative value obviously corresponds to sun below horizon).
• if elevation-high and elevation-low have the same value, any sun angle will be considered either «100% day» or «100% night». Hence, no day/night transition. On the other hand, if elevation-high is greater than elevation-low, every sun angle between them will correspond to some transition state, like «43% day».

[kousu]

I was just about to come here to file a feature request that the startup transition could be instant (so that each startx doesn't have an obnoxious blaring fluorescent-blue glow with it), and then I found this! I definitely misunderstood the manpage.

Why isn't transition=0 the default? Actually, why is it even an option? I was expecting that redshift would set the screen temp as a function of time: flat during the day, a linear ramp for the times between elevation-high and elevation-low, flat during the night, then another linear ramp to get back up to day. It was interpretting transition=0 as "make the ramps 0-width", or turn the design into a step function. It would make more sense if you just got rid of the option entirely, I think.