Creating Custom Theme Feature Support

Since WordPress version 2.9 theme developers have taken advantage of the add_theme_support feature. Built-in theme features include custom header images, custom backgrounds, post formats, and more. However, we’ve also been given a filter in the current_theme_supports function that allows us to expand theme feature support beyond the built-in options.

The most obvious, and simplest, usage of theme features is to first use add_theme_support to register a feature supported by your theme. Then we can verify the feature is supported with the conditional current_theme_supports function. For example:

Expanding Custom Theme Features With Arguments

That’s all fine and dandy, but what if you have a lot of potential theme features that could vary depending on the theme? You might be creating a theme extending plugin or theme extension for plugins to use, perhaps. Instead of listing out a ton of add_theme_support declarations (and their conditionals all over the place), let’s simplify it to a single declaration, shall we?

Thanks to the way current_theme_supports is written, we can create a single feature and pass through a multitude of “sub-features” in an array with a second $arguments variable like this: add_theme_support( $feature, $arguments );. In order for this to be useful, however, we’ll need to amend the current_theme_supports function to accept the secondary features, using a feature-specific filter, then we can use it accordingly.

For example, I’m creating a theme extending plugin. Each theme will use a single line to add theme support for a multitude of features. First, we’ll create a function to add the arguments as acceptable values in the current_theme_supports function. Then we’ll add the features to our theme.

Now I can use the current_theme_supports function in my plugin/theme to add functionality that is supported, like this:

And there you have it! You’ve easily extended this core function to further your theme development powers.

Expanding The require_if_theme_supports Function

Another great function related to theme features is the require_if_theme_supports function. Justin Tadlock has a great write up on theme supported features that touches on this function.

Basically, it allows you to conditionally require another file – if theme supports X, include file Y. What if you want to use this function with our example above? Well, you can, but you can’t pass our new sub-features through it. What if you only want to include a file if the custom-footer-text is supported? I’ve written another function you can use in a similar manner. Instead of the main feature, use the sub feature.

Image Credit: Express Monorail, cc