Much is the same, but not all, and in this small article I would like to briefly explain how you set settings in the database when you activate a Plugin.

The best case for this is a Function of WordPress, which is triggered when activating a plugin register_activation_hook(). This Function will be called in init or constructor of the Plugin. In the called Function are the functions to store the settings of WordPress in the table options - add_option(). In Multisite there is also a function for it - add_site_option().

Now you have to separate, if the Plugin is activated within the Network, in the management of Multisite installation, or if it is only used in one of the blogs in the network or a single installation. There are currently no functions, but a value that is passed. The following example illustrates it:

register_activation_hook( __FILE__, 'fb_add_config' );
function fb_add_config() {

	$data = array(
		'active' => 0,
		'radio'  => 0,
		'link'   => 1,
		'theme'  => 1,
		'role'   => 'administrator',
		'unit'   => 1,
	);
	// if is active in network of multisite
	if ( is_multisite() && isset($_GET['networkwide']) && 1 == $_GET['networkwide'] ) {
		add_site_option( 'my_settings_id', $data );
	} else {
		add_option( 'my_settings_id', $data );
	}
}

The query of the value in the global GET can be integrated in the long time ago mentioned solution for Multisite and settings.

To solve other queries in a Multisite environment and to remove the setup or integrate menus in the admin area, the function is_plugin_active_for_network() is useful.

if ( is_multisite() && is_plugin_active_for_network( plugin_basename( __FILE__ ) ) )
	$values = get_site_option( 'my_settings_id' );
else
	$values = get_option( 'my_settings_id' );

The following small Plugin may extend to different roles or authorization objects, so that you can upload, depending on the role, different types of files in the system - current_user_can().

Anyone interested in the currently allowed types, you can return the array of the first function or look into the function get_allowed_mime_types() in wp-includes/functions.php.

<?php
/**
 * Plugin Name: Restrict mime types
 * Plugin URI:  http://wpengineer.com/?p=2369
 * Description: Restrict list of allowed mime types and file extensions.
 * Version:     1.0.0
 * License:     GPLv3
 * Author:      Frank Bültge
 * Author URI:  http://bueltge.de/
 */

 // This file is not called from WordPress. We don't like that.
! defined( 'ABSPATH' ) and exit;

// If the function exists this file is called as upload_mimes.
// We don't do anything then.
if ( ! function_exists( 'fb_restrict_mime_types' ) ) {

	add_filter( 'upload_mimes', 'fb_restrict_mime_types' );
	/**
	 * Retrun allowed mime types
	 *
	 * @see     function get_allowed_mime_types in wp-includes/functions.php
	 * @param   array Array of mime types
	 * @return  array Array of mime types keyed by the file extension regex corresponding to those types.
	 */
	function fb_restrict_mime_types( $mime_types ) {

		$mime_types = array(
			'pdf' => 'application/pdf',
			'doc|docx' => 'application/msword',
		);

		return $mime_types;
	}
}

// If the function exists this file is called as post-upload-ui.
// We don't do anything then.
if ( ! function_exists( 'fb_restrict_mime_types_hint' ) ) {
	// add to wp
	add_action( 'post-upload-ui', 'fb_restrict_mime_types_hint' );
	/**
	 * Get an Hint about the allowed mime types
	 *
	 * @return  void
	 */
	function fb_restrict_mime_types_hint() {

		echo '<br />';
		_e( 'Accepted MIME types: PDF, DOC/DOCX' );
	}
}

// example on admin init, control about register_activation_hook()
add_action( 'admin_init', 'fb_activate_plugins' );
// the exmple function
function fb_activate_plugins() {

	if ( ! current_user_can('activate_plugins') )
		wp_die(__('You do not have sufficient permissions to activate plugins for this site.'));
	$plugins = FALSE;
	$plugins = get_option('active_plugins'); // get active plugins

	if ( $plugins ) {
		// plugins to active
		$pugins_to_active = array(
			'hello.php', // Hello Dolly
			'adminimize/adminimize.php', // Adminimize
			'akismet/akismet.php' // Akismet
		);

		foreach ( $pugins_to_active as $plugin ) {
			if ( ! in_array( $plugin, $plugins ) ) {
				array_push( $plugins, $plugin );
				update_option( 'active_plugins', $plugins );
			}
		}

	} // end if $plugins

}

The following function and its hook provides a direct output of the string of the Plugin file on the Plugin page in your backend, so please use it only for a quick finding.

add_filter( 'plugin_row_meta', 'fb_get_plugin_string', 10, 4 );
function fb_get_plugin_string( $plugin_meta, $plugin_file, $plugin_data, $status ) {
	// echo plugin file string
	echo '<code>' . $plugin_file . '</code><br>';
	return $plugin_meta;
}

That means: Are we in the time zone of Berlin, the local time is UTC +1. Are we performing a scheduled event, it will always be one hour after the actual time we like to execute. To change this, we use the following function:

function get_offset_to_gmt_in_seconds() {

	$current_timezone_offset = get_option( 'gmt_offset' );
	$offset = $current_timezone_offset * 3600;

	return $offset;
}

But in my opinion the editor has an usability issue.
Every time you save a post the scroll position of the editor will be on top again. If you want to continue writing the post you have first to find he old position again. This can be time-consuming.

Save editor scroll position on saving

To avoid this behavior I have written a snippet which I want to share now with you.

<?php
/**
 * The class will help you to recover the old scoll position in your Editor.
 * Either HTML or visuel editor.
 */
final class Preserve_Editor_Scroll_Position {
	/**
	 * Init
	 */
	public static function init() {
		add_filter( 'redirect_post_location', array( __CLASS__, 'add_query_arg' ) );
		add_action( 'edit_form_advanced', array( __CLASS__, 'add_input_field' ) );
		add_action( 'edit_page_form', array( __CLASS__, 'add_input_field' ) );
		add_filter( 'tiny_mce_before_init', array( __CLASS__, 'extend_tiny_mce' ) );
	}

	/**
	 * Adds a hidden input field for scrolltop value
	 */
	public static function add_input_field() {
		$position = ! empty( $_GET['scrollto'] ) ? $_GET['scrollto'] : 0;

		printf( '<input type="hidden" id="scrollto" name="scrollto" value="%d"/>', esc_attr( $position ) );

		// Print Javascript data
		add_action( 'admin_print_footer_scripts', array( __CLASS__, 'print_js' ), 55 ); // Print after Editor JS.
	}

	/**
	 * Extend TinyMCE config with a setup function
	 */
	public static function extend_tiny_mce( $init ) {
		if ( 'tinymce' == wp_default_editor() )
			$init['setup'] = 'rich_scroll';

		return $init;
	}

	/**
	 * Returns redirect url with query arg for scroll position
	 */
	public static function add_query_arg( $location ) {
		if ( ! empty( $_POST['scrollto'] ) )
			$location = add_query_arg( 'scrollto', (int) $_POST['scrollto'], $location );

		return $location;
	}

	/**
	 * Prints Javascript data
	 */
	public static function print_js() {
		?>
	<script>
	( function( $ ) {
		$( '#post' ).submit( function() {
			scrollto =
				$( '#content' ).is( ':hidden' ) ?
				$( '#content_ifr' ).contents().find( 'body' ).scrollTop() :
				$( '#content' ).scrollTop();

			$( '#scrollto' ).val( scrollto );
		} );

		$( '#content' ).scrollTop( $( '#scrollto' ).val() );
	} )( jQuery );

	function rich_scroll( ed ) {
		ed.onInit.add( function() {
			jQuery( '#content_ifr' ).contents().find( 'body' ).scrollTop( jQuery( '#scrollto' ).val() );
		} );
	};
	</script>
		<?php
	}
}
add_action( 'plugins_loaded', array( 'Preserve_Editor_Scroll_Position', 'init' ) );

If you want you can create your own plugin with this snippet or you can download the plugin Preserve Editor Scroll Position.

// for enabling/disabling theme/plugin editor
define( 'DISALLOW_FILE_EDIT', TRUE );

The second constant presented here prohibits editing, modifying or changing the core files, Plugins or Themes. In this context the menu entries in the backend are not visible or usable. Thus the update is not so easy to do and clients and unauthenticated users are blocked quickly.

// Disallow anything that creates, deletes, or edits core, plugin, or theme files.
// Files in uploads are excepted.
define( 'DISALLOW_FILE_MODS', TRUE );

In this context there are two constants that are useful now and then.

In various contexts it is very useful that all users have the option of: to write unfiltered HTML, in all aspects and this can also be easily implemented via constants:

// Disallow unfiltered_html for all users, even admins and super admins
DISALLOW_UNFILTERED_HTML

Similar existing for uploads:

// Allow uploads of filtered file types to users with administrator role
ALLOW_UNFILTERED_UPLOADS

The constants belong in the wp-config.php of the installation.

If you are in the environment of customers, it may be that you don't want the feature pointer - different scenarios are possible. But here it also relies on the WordPress hooks so you can intervene in various ways. One idea is to adjust the user settings of the user, as the feature pointer is using Javascript to drop an option in the table, so that the user does not read the instructions again. Alternatively, you can disable it via hook, following solution paste into a small Plugin or the functions.php of your theme (whereas the second solution isn't the best).

<code>
add_filter( 'show_wp_pointer_admin_bar', '__return_false' );
</code>

If you don't have the admin bar not active, then it won't show a feature pointer to it.

Also you can use the hooks to create your own feature pointer. Without adjustment in the design and position is the following simple example conceivable. If the position is changed, it is sufficient to adapt the script section JS-function pointer() in the PHP function get_content_in_wp_pointer(). The function pointer() can be controlled by various parameters (content, position, arrow) .

function get_content_in_wp_pointer() {
	$pointer_content  = '<h3>' . __( 'WP Pointer with version 3.3.', 'my_textdomain' ) . '</h3>';
	$pointer_content .= '<p>' . __( 'Add your own informations to WP Pointer.', 'my_textdomain' ) . '</p>';

?>
<script type="text/javascript">
//<![CDATA[
jQuery(document).ready( function($) {
	$('#wpadminbar').pointer({
		content: '<?php echo $pointer_content; ?>',
		position: {
			my: 'left top',
			at: 'center bottom',
			offset: '-25 0'
		},
		close: function() {
			setUserSetting( 'p1', '1' );
		}
	}).pointer('open');
});
//]]>
</script>
<?php
}

function fb_enqueue_wp_pointer( $hook_suffix ) {
	$enqueue = FALSE;

	$admin_bar = get_user_setting( 'p1', 0 ); // check settings on user
	// check if admin bar is active and default filter for wp pointer is true
	if ( ! $admin_bar && apply_filters( 'show_wp_pointer_admin_bar', TRUE ) ) {
		$enqueue = TRUE;
		add_action( 'admin_print_footer_scripts', 'get_content_in_wp_pointer' );
	}
	// in true, include the scripts
	if ( $enqueue ) {
		wp_enqueue_style( 'wp-pointer' );
		wp_enqueue_script( 'wp-pointer' );
		wp_enqueue_script( 'utils' ); // for user settings
	}
}
add_action( 'admin_enqueue_scripts', 'fb_enqueue_wp_pointer' );

Please note: The implementation is based on a nightly build of WordPress, not the final Release 3.3 and thus might have some changes or other solutions are possible in a later version. Therefore, please validate according to the version of WordPress the solution. As a tip this should be enough - anything else is creativity and your skills.

/**
 * Remove a top level admin menu
 *
 * @param string $menu_slug The slug of the menu
 * @return array|bool The removed menu on success, False if not found
 */
remove_menu_page( $menu_slug )

/**
 * Remove an admin submenu
 *
 * @param string $menu_slug The slug for the parent menu
 * @param string $submenu_slug The slug of the submenu
 * @return array|bool The removed submenu on success, False if not found
 */
remove_submenu_page( $menu_slug, $submenu_slug ) {

It's easy to remove menu entries and it is not necessary anymore to read the arrays $menu and $submenu. Until now you had to search for them in the array and remove them via unset() from the array. Alternatively you were also able to find the entry on the basis of a key - the above new features make this unnecessary and as a parameter value only the "slug" is passed, which can be found in the link or the URL of the backend. A small example, where we remove the entries to the comments and the submenu-page discussion will show the new possibilities.

function fb_remove_menu_entries () {
	// with WP 3.1 and higher
	if ( function_exists( 'remove_menu_page' ) ) {
		remove_menu_page( 'edit-comments.php' );
		remove_submenu_page( 'options-general.php', 'options-discussion.php' );
	} else {
		// unset comments
		unset( $GLOBALS['menu'][25] );
		// unset menuentry Discussion
		unset( $GLOBALS['submenu']['options-general.php'][25] );
	}
}
add_action( 'admin_menu', 'fb_remove_menu_entries' );

The above code provides a simple solution, removed the two entries and also has a fallback for WordPress, smaller version 3.1. It is also conceivable that the removal is also connected with user rights

if ( function_exists( 'remove_menu_page' ) && ! current_user_can( 'manage_options' ) ) {

so it would be possible to optimize the menu explicitly for a user. Alternatively, the plug Adminimize helps and facilitates the job via admin area.
You can also read about this topic on Justin's post, but my post was an older draft and now was published - the topic is worth it.

You can find the Plugin in Github and it would be great if you expand it, add new ideas and possibilities to it: - github.com/bueltge/WordPress-Admin-Style

The following code belongs into a Plugin and should be placed in the folder mu-plugins.

class Add_Blog_ID {

	public static function init() {
		$class = __CLASS__ ;

		if ( empty( $GLOBALS[ $class ] ) )
			$GLOBALS[ $class ] = new $class;
	}

	public function __construct() {

		add_filter( 'wpmu_blogs_columns', array( $this, 'get_id' ) );
		add_action( 'manage_sites_custom_column', array( $this, 'add_columns' ), 10, 2 );
		add_action( 'manage_blogs_custom_column', array( $this, 'add_columns' ), 10, 2 );
		add_action( 'admin_footer', array( $this, 'add_style' ) );
	}

	public function add_columns( $column_name, $blog_id ) {

		if ( 'blog_id' === $column_name )
			echo $blog_id;

		return $column_name;
	}

	// Add in a column header
	public function get_id( $columns ) {

		$columns['blog_id'] = __('ID');

		return $columns;
	}

	public function add_style() {

		echo '<style>#blog_id { width:7%; }</style>';
	}
}
add_action( 'init', array( 'Add_Blog_ID', 'init' ) );