Ticket #23819: 23819.1.diff

wp-content/themes/twentythirteen/functions.php

@@ -592 +592 @@
  * Adds support for a custom header image.
  */
 require( get_template_directory() . '/inc/custom-header.php' );
+
+/**
+ * Adds back compat handling for WP versions pre-3.6.
+ */
+require( get_template_directory() . '/inc/back-compat.php' );

wp-content/themes/twentythirteen/inc/back-compat.php

@@ +1 @@
+<?php
+/**
+ * Prevent switching to Twenty Thirteen on old versions of WordPress. Switches
+ * to the previously activated theme or the default theme.
+ */
+function twentythirteen_switch_theme( $theme_name, $theme ) {
+        if ( version_compare( $GLOBALS['wp_version'], '3.6', '>=' ) )
+                return;
+
+        if ( 'twentythirteen' != $theme->template )
+                switch_theme( $theme->template, $theme->stylesheet );
+        elseif ( 'twentythirteen' != WP_DEFAULT_THEME )
+                switch_theme( WP_DEFAULT_THEME );
+
+        unset( $_GET['activated'] );
+        add_action( 'admin_notices', 'twentythirteen_upgrade_notice' );
+}
+add_action( 'after_switch_theme', 'twentythirteen_switch_theme', 10, 2 );
+
+function twentythirteen_upgrade_notice() {
+        $message = sprintf( __( 'Twenty Thirteen requires at least WordPress version 3.6. You are running version %s. Please upgrade and try again.' ), $GLOBALS['wp_version'] );
+        printf( '<div class="error"><p>%s</p></div>', $message );
+}
+ No newline at end of file