Source

File: wp-admin/includes/template.php

function do_meta_boxes( $screen, $context, $object ) {
	global $wp_meta_boxes;
	static $already_sorted = false;

	if ( empty( $screen ) ) {
		$screen = get_current_screen();
	} elseif ( is_string( $screen ) ) {
		$screen = convert_to_screen( $screen );
	}

	$page = $screen->id;

	$hidden = get_hidden_meta_boxes( $screen );

	printf( '<div id="%s-sortables" class="meta-box-sortables">', esc_attr( $context ) );

	// Grab the ones the user has manually sorted.
	// Pull them out of their previous context/priority and into the one the user chose.
	$sorted = get_user_option( "meta-box-order_$page" );

	if ( ! $already_sorted && $sorted ) {
		foreach ( $sorted as $box_context => $ids ) {
			foreach ( explode( ',', $ids ) as $id ) {
				if ( $id && 'dashboard_browser_nag' !== $id ) {
					add_meta_box( $id, null, null, $screen, $box_context, 'sorted' );
				}
			}
		}
	}

	$already_sorted = true;

	$i = 0;

	if ( isset( $wp_meta_boxes[ $page ][ $context ] ) ) {
		foreach ( array( 'high', 'sorted', 'core', 'default', 'low' ) as $priority ) {
			if ( isset( $wp_meta_boxes[ $page ][ $context ][ $priority ] ) ) {
				foreach ( (array) $wp_meta_boxes[ $page ][ $context ][ $priority ] as $box ) {
					if ( false === $box || ! $box['title'] ) {
						continue;
					}

					$block_compatible = true;
					if ( is_array( $box['args'] ) ) {
						// If a meta box is just here for back compat, don't show it in the block editor.
						if ( $screen->is_block_editor() && isset( $box['args']['__back_compat_meta_box'] ) && $box['args']['__back_compat_meta_box'] ) {
							continue;
						}

						if ( isset( $box['args']['__block_editor_compatible_meta_box'] ) ) {
							$block_compatible = (bool) $box['args']['__block_editor_compatible_meta_box'];
							unset( $box['args']['__block_editor_compatible_meta_box'] );
						}

						// If the meta box is declared as incompatible with the block editor, override the callback function.
						if ( ! $block_compatible && $screen->is_block_editor() ) {
							$box['old_callback'] = $box['callback'];
							$box['callback']     = 'do_block_editor_incompatible_meta_box';
						}

						if ( isset( $box['args']['__back_compat_meta_box'] ) ) {
							$block_compatible = $block_compatible || (bool) $box['args']['__back_compat_meta_box'];
							unset( $box['args']['__back_compat_meta_box'] );
						}
					}

					$i++;
					// get_hidden_meta_boxes() doesn't apply in the block editor.
					$hidden_class = ( ! $screen->is_block_editor() && in_array( $box['id'], $hidden, true ) ) ? ' hide-if-js' : '';
					echo '<div id="' . $box['id'] . '" class="postbox ' . postbox_classes( $box['id'], $page ) . $hidden_class . '" ' . '>' . "\n";

					echo '<div class="postbox-header">';
					echo '<h2 class="hndle">';
					if ( 'dashboard_php_nag' === $box['id'] ) {
						echo '<span aria-hidden="true" class="dashicons dashicons-warning"></span>';
						echo '<span class="screen-reader-text">' . __( 'Warning:' ) . ' </span>';
					}
					echo "{$box['title']}";
					echo "</h2>\n";

					if ( 'dashboard_browser_nag' !== $box['id'] ) {
						$widget_title = $box['title'];

						if ( is_array( $box['args'] ) && isset( $box['args']['__widget_basename'] ) ) {
							$widget_title = $box['args']['__widget_basename'];
							// Do not pass this parameter to the user callback function.
							unset( $box['args']['__widget_basename'] );
						}

						echo '<div class="handle-actions hide-if-no-js">';

						echo '<button type="button" class="handle-order-higher" aria-disabled="false" aria-describedby="' . $box['id'] . '-handle-order-higher-description">';
						echo '<span class="screen-reader-text">' . __( 'Move up' ) . '</span>';
						echo '<span class="order-higher-indicator" aria-hidden="true"></span>';
						echo '</button>';
						echo '<span class="hidden" id="' . $box['id'] . '-handle-order-higher-description">' . sprintf(
							/* translators: %s: Meta box title. */
							__( 'Move %s box up' ),
							$widget_title
						) . '</span>';

						echo '<button type="button" class="handle-order-lower" aria-disabled="false" aria-describedby="' . $box['id'] . '-handle-order-lower-description">';
						echo '<span class="screen-reader-text">' . __( 'Move down' ) . '</span>';
						echo '<span class="order-lower-indicator" aria-hidden="true"></span>';
						echo '</button>';
						echo '<span class="hidden" id="' . $box['id'] . '-handle-order-lower-description">' . sprintf(
							/* translators: %s: Meta box title. */
							__( 'Move %s box down' ),
							$widget_title
						) . '</span>';

						echo '<button type="button" class="handlediv" aria-expanded="true">';
						echo '<span class="screen-reader-text">' . sprintf(
							/* translators: %s: Meta box title. */
							__( 'Toggle panel: %s' ),
							$widget_title
						) . '</span>';
						echo '<span class="toggle-indicator" aria-hidden="true"></span>';
						echo '</button>';

						echo '</div>';
					}
					echo '</div>';

					echo '<div class="inside">' . "\n";

					if ( WP_DEBUG && ! $block_compatible && 'edit' === $screen->parent_base && ! $screen->is_block_editor() && ! isset( $_GET['meta-box-loader'] ) ) {
						$plugin = _get_plugin_from_callback( $box['callback'] );
						if ( $plugin ) {
							?>
							<div class="error inline">
								<p>
									<?php
										/* translators: %s: The name of the plugin that generated this meta box. */
										printf( __( "This meta box, from the %s plugin, isn't compatible with the block editor." ), "<strong>{$plugin['Name']}</strong>" );
									?>
								</p>
							</div>
							<?php
						}
					}

					call_user_func( $box['callback'], $object, $box );
					echo "</div>\n";
					echo "</div>\n";
				}
			}
		}
	}

	echo '</div>';

	return $i;

}