This patch adds the ability to theme the amount of color difference of every other row in the outliner. The option appears as a color with alpha in the outliner section of the theme settings. The color is lightly overlayed onto every other row in the outliner. Previously, every other row was hard-coded to be 6 values brighter than their adjecent rows. With this patch, users have more control over the difference in color. For example, a user could choose to remove the color difference between the rows (by making this option transparent) and have a solid background color in the outliner.
Functionality wise is a +1. I'm usually against adding new theme settings (we have so many), but this one helps readability and even allows disabling the overlay altogether.
The only thing I'm not sure about is the name of the variable TH_ROW_OVERLAY, but I'll leave that to developers. What do you think @Brecht Van Lommel (brecht)?
This setting could even be introduced in the future for other editors with odd/even rows like the file browser.
Not sure about the name TH_ROW_OVERLAY, since it doesn't overlay all rows. Wouldn't it be more like variation? odd? interleaved?
TH_ROW_VARIATION TH_ROW_ODD TH_ROW_INTERLEAVE
Keeping in mind this could be used for the file browser as well.