Clean out layout columns API in WP_Screen.

* Move layout column setup into render_screen_meta() so that the number of columns is available earlier.
* Store the user provisioned number of columns in an instance var.
* Access the var with get_columns()
* Move all templates away from the screen_layout_columns global to the get_columns() method.
* Deprecate the global
* Remove the no longer needed check for 'auto' in the user option.
* Cast the user option to an int.

Props griffinjt
fixes #20506


git-svn-id: http://svn.automattic.com/wordpress/trunk@20579 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/edit-form-advanced.php

@@ -277,7 +277,7 @@ wp_nonce_field( 'closedpostboxes', 'closedpostboxesnonce', false );
 
 <div id="poststuff">
 
-<div id="post-body" class="metabox-holder columns-<?php echo 1 == $screen_layout_columns ? '1' : '2'; ?>">
+<div id="post-body" class="metabox-holder columns-<?php echo 1 == get_current_screen()->get_columns() ? '1' : '2'; ?>">
 <div id="post-body-content">
 <?php if ( post_type_supports($post_type, 'title') ) { ?>
 <div id="titlediv">

wp-admin/edit-link-form.php

@@ -77,7 +77,7 @@ wp_nonce_field( 'meta-box-order', 'meta-box-order-nonce', false ); ?>
 
 <div id="poststuff">
 
-<div id="post-body" class="metabox-holder columns-<?php echo 1 == $screen_layout_columns ? '1' : '2'; ?>">
+<div id="post-body" class="metabox-holder columns-<?php echo 1 == get_current_screen()->get_columns() ? '1' : '2'; ?>">
 <div id="post-body-content">
 <div id="namediv" class="stuffbox">
 <h3><label for="link_name"><?php _ex('Name', 'link name') ?></label></h3>

wp-admin/includes/dashboard.php

@@ -193,10 +193,8 @@ function _wp_dashboard_control_callback( $dashboard, $meta_box ) {
  * @since 2.5.0
  */
 function wp_dashboard() {
-	global $screen_layout_columns;
-
 	$screen = get_current_screen();
-	$class = 'columns-' . $screen_layout_columns;
+	$class = 'columns-' . get_current_screen()->get_columns();
 
 ?>
 <div id="dashboard-widgets" class="metabox-holder <?php echo $class; ?>">

wp-admin/includes/screen.php

@@ -225,6 +225,15 @@ final class WP_Screen {
 	 */
 	public $base;
 
+	/**
+	 * The number of columns to display. Access with get_columns().
+	 *
+	 * @since 3.4.0
+	 * @var int
+	 * @access private
+	 */
+	private $columns = 0;
+
 	/**
 	 * The unique ID of the screen.
 	 *
@@ -678,6 +687,23 @@ final class WP_Screen {
 		$this->_help_sidebar = $content;
 	}
 
+	/**
+	 * Gets the number of layout columns the user has selected.
+	 *
+	 * The layout_columns option controls the max number and default number of
+	 * columns. This method returns the number of columns within that range selected
+	 * by the user via Screen Options. If no selection has been made, the default
+	 * provisioned in layout_columns is returned. If the screen does not support
+	 * selecting the number of layout columns, 0 is returned.
+	 *
+	 * @since 3.4.0
+	 *
+	 * @return int Number of columns to display.
+	 */
+	public function get_columns() {
+		return $this->columns;
+	}
+
 	/**
 	 * Render the screen's help section.
 	 *
@@ -773,6 +799,22 @@ final class WP_Screen {
 				</div>
 			</div>
 		<?php
+		// Setup layout columns
+
+		// Back compat for plugins using the filter instead of add_screen_option()
+		$columns = apply_filters( 'screen_layout_columns', array(), $this->id, $this );
+
+		if ( ! empty( $columns ) && isset( $columns[ $this->id ] ) )
+			$this->add_option( 'layout_columns', array('max' => $columns[ $this->id ] ) );
+
+		if ( $this->get_option( 'layout_columns' ) ) {
+			$this->columns = (int) get_user_option("screen_layout_$this->id");
+	
+			if ( ! $this->columns && $this->get_option( 'layout_columns', 'default' ) )
+				$this->columns = $this->get_option( 'layout_columns', 'default' );
+		}
+		$GLOBALS[ 'screen_layout_columns' ] = $this->columns; // Set the gobal for back-compat.
+
 		// Add screen options
 		if ( $this->show_screen_options() )
 			$this->render_screen_options();
@@ -907,27 +949,12 @@ final class WP_Screen {
 	 * @since 3.3.0
 	 */
 	function render_screen_layout() {
-		global $screen_layout_columns;
+		if ( ! $this->get_option('layout_columns') )
-
-		// Back compat for plugins using the filter instead of add_screen_option()
-		$columns = apply_filters( 'screen_layout_columns', array(), $this->id, $this );
-
-		if ( ! empty( $columns ) && isset( $columns[ $this->id ] ) )
-			$this->add_option( 'layout_columns', array('max' => $columns[ $this->id ] ) );
-
-		if ( ! $this->get_option('layout_columns') ) {
-			$screen_layout_columns = 0;
 			return;
-		}
 
-		$screen_layout_columns = get_user_option("screen_layout_$this->id");
+		$screen_layout_columns = $this->get_columns();
 		$num = $this->get_option( 'layout_columns', 'max' );
 
-		if ( ! $screen_layout_columns || 'auto' == $screen_layout_columns ) {
-			if ( $this->get_option( 'layout_columns', 'default' ) )
-				$screen_layout_columns = $this->get_option( 'layout_columns', 'default' );
-		}
-
 		?>
 		<h5 class="screen-layout"><?php _e('Screen Layout'); ?></h5>
 		<div class='columns-prefs'><?php