how to tell a Custom Theme vs Color Theme?

Question

I am considering changing the look of my emacs (just default state right now). I've read that Color Theme is an older approach but has its own advantages compared to Custom Theme (newer approach). One of the benefits of Color Theme seems to be the ability to completely turn it off and revert back to default state. Apparently, Custom Theme cannot be switched off in this manner.

Because Color Themes are undo-able, I want to install a few Color Themes to try out. But, when I start looking around, I see that a lot of Color Themes also have a Custom Theme version(?). How can I tell whether I'm installing a Color Theme vs a Custom Theme? Is there something in the .el file OR the way in which I have to alter my .emacs file that will tell me definitively?

Answer 1

(Variable color-themes is a list of your color themes. A given color theme is a function.)

You can use command color-theme-analyze-defun to check whether a function definition (defun) at point defines a color theme. It's defined in color-theme.el.

Here is its doc string:

Once you have a color-theme printed, check for missing faces.

This is used by maintainers who receive a color-theme submission and want to make sure it follows the guidelines by the color-theme author.