Building Child Themes

• Aaron Jorbin
• http://aaron.jorb.in
• @aaronjorbin
• WordCamp Chicago 2010

What Are Child Themes

• Inherit Templates From a Parent unless you say otherwise
• As little as a style.css file, as much as you want it to be
• Template: PARENT DIRNAME

Why Use Child Themes

• Good Developers are Lazy Developers
• Speed Matters
• Makes Updates Easier

Examples

Twenty Ten

• READ THE 2010 SOURCE!
• PHPDOCS and conversational docs
• A tutorial in and of itself

get_template_part

• Used to get an overridable file
• Parameter 1: File ; Parameter 2: Context
• Example: get_template_part( 'loop', 'index' );
  • loop-index.php in child theme
  • loop-index.php in parent theme
  • loop.php in child theme
  • loop.php in parent theme

Override or Remove

Child Theme's functions.php file loaded first

If removing an action or filter, wrap it in a function and hook it earlier

function twentyten_excerpt_length( $length ) {
	return 40;
}
add_filter( 'excerpt_length', 'twentyten_excerpt_length' );
			

function jorbin_remove_excerpt_length(){
	remove_filter( 'excerpt_length', 'twentyten_excerpt_length' );
}
add_action( 'init', 'jorbin_remove_excerpt_length' );
			

Override a function

if ( ! function_exists( 'twentyten_setup' ) ):
function twentyten_setup() {
		

Thirty Ten Style

/*
Theme Name: Thirty Ten
Theme URI: http://aaron.jorb.in/thirty-ten
Description: A child theme of 2010.
Author: Aaron Jorbin based on work by the WordPress team
Author URI: http://aaron.jorb.in/
Version: 1.1
Template: twentyten
*/

@import url('../twentyten/style.css');
		

Same as a regular theme, except we define a Template (which is the Parent's Directory) and then import the parents style sheet

Move the Menu, Change the Link Colors

/* Move menu to be above image */
#header #access{
top: -240px;
position: relative;
}
#site-title {margin:0 0 44px;}
/* Change our default link colors */
a:link{color:#fdb120;}
a:visited{color:#d00c0d;}
a:hover{color:#1143d8;}
a:active{color:#a67942;}
			

Thematic

Helpful Hints

• Hook into init and conditionally add or remove actions/filters
• Use filters as actions
• Reduce, Reuse, Recycle
• Pick a good parent