Some users of Firefox and the RedShift theme may have noticed that the latest version of Red Shift is not yet compatible with the latest version of FF.
As usual, developers set a "maximum version" number in the code of their extension or theme so that when FF is updated, the extension (even if it might be functional) will be disabled. This is to prevent conflicts that may arise in FF code that the extension dev may not have prepared for. The developer is usually apprised if their extension becomes listed as incompatible. Once they are aware, they have the opportunity to check it for bugs, and if compatible, increase the maximum version in the code (along with the extension/theme build version) and resubmit it to Mozilla. Now, more often than not, there is no need for major code revision, and, in effect, the assigned maximum version turns out to have been an overcautious choice (rather than set the maximum version to a higher build of FF). Of course, code revision is necessary along the way for any extension to remain compatible with Firefox, but assigning a maxversion is often arbitrary, and the likelihood that major revision is necessary with the passing of a specific build number is not high.
Well, I thought that might be the case here, and I revised the maxversion in the latest RedShift xpi to be compatible. I currently have RedShift V4 (6.0.2) running on Firefox 4 (9.0.1) without issues.
To make it so, once has to change the maxVersion field in a file called install.rdf. You may notice it in passing when you apply the mod I posted above. It is essentially a text file that can be opened with notepad.
If you wish to try an apply the same fix for current compatibility (RedShift is reported as incompatible on your version of FF), then you need to shut down FF, and use my previous instructions to get to the install.rdf file. Open it in notepad, and make sure to change the maxversion to the following:
If you do this, make sure to re-enable the theme afterward in FF and restart again.
If you have a current version of Firefox and attempt to install RedShift for the first time, it may not work. In that situation, save the xpi to your PC, and make the changes in the file (including the image mod while you're at it), and re-save it. You can open Firefox and then drag and drop it into the browser for an install.
I haven't had any issues after doing this, but, as always, you do so at your own risk. Changing an extension maxversion to suit an updated version of FF usually goes smoothly, but on occasion, there are some conflicts that require more code changes to be compatible with a current FF build. As the guinea pig here, I have survived unscathed with full functionality. Of course, you can wait until the RedShift devs update the theme, but you can try this for now if you can't wait.