If you inspect the value of $in you should get something like:
Array
(
[mode] => exact
[width] => 100%
[theme] => advanced
[skin] => wp_theme
[language] => en
[theme_advanced_toolbar_location] => top
[theme_advanced_toolbar_align] => left
[theme_advanced_statusbar_location] => bottom
[theme_advanced_resizing] => 1
[theme_advanced_resize_horizontal] =>
[dialog_type] => modal
[formats] => {
alignleft : [
{selector : 'p,h1,h2,h3,h4,h5,h6,td,th,div,ul,ol,li', styles : {textAlign : 'left'}},
{selector : 'img,table', classes : 'alignleft'}
],
aligncenter : [
{selector : 'p,h1,h2,h3,h4,h5,h6,td,th,div,ul,ol,li', styles : {textAlign : 'center'}},
{selector : 'img,table', classes : 'aligncenter'}
],
alignright : [
{selector : 'p,h1,h2,h3,h4,h5,h6,td,th,div,ul,ol,li', styles : {textAlign : 'right'}},
{selector : 'img,table', classes : 'alignright'}
],
strikethrough : {inline : 'del'}
}
[relative_urls] =>
[remove_script_host] =>
[convert_urls] =>
[remove_linebreaks] => 1
[gecko_spellcheck] => 1
[fix_list_elements] => 1
[keep_styles] =>
[entities] => 38,amp,60,lt,62,gt
[accessibility_focus] => 1
[media_strict] =>
[paste_remove_styles] => 1
[paste_remove_spans] => 1
[paste_strip_class_attributes] => all
[paste_text_use_dialog] => 1
[webkit_fake_resize] =>
[preview_styles] => font-family font-weight text-decoration text-transform
[schema] => html5
[wpeditimage_disable_captions] =>
[wp_fullscreen_content_css] => http://example.com/wp-includes/js/tinymce/plugins/wpfullscreen/css/wp-fullscreen.css
[plugins] => inlinepopups,tabfocus,paste,media,fullscreen,wordpress,wpeditimage,wpgallery,wplink,wpdialogs,wpfullscreen
[content_css] => http://example.com/wp-content/themes/twentytwelve/editor-style.css,http://fonts.googleapis.com/css?family=Open+Sans:400italic%2C700italic%2C400%2C700&subset=latin%2Clatin-ext
[elements] => content
[wpautop] => 1
[apply_source_formatting] =>
[theme_advanced_buttons1] => bold,italic,strikethrough,bullist,numlist,blockquote,justifyleft,justifycenter,justifyright,link,unlink,wp_more,spellchecker,wp_fullscreen,wp_adv
[theme_advanced_buttons2] => formatselect,underline,justifyfull,forecolor,pastetext,pasteword,removeformat,charmap,outdent,indent,undo,redo,wp_help
[theme_advanced_buttons3] =>
[theme_advanced_buttons4] =>
[tabfocus_elements] => insert-media-button,save-post
[body_class] => content post-type-post post-status-publish post-format-standard
[theme_advanced_resizing_use_cookie] =>
[wordpress_adv_hidden] =>
)
The last item wordpress_adv_hidden gives you the possibility to hide/show the kitchen sink
/**
* Modify TinyMCE
*
* @param array $in
* @return array $in
*/
function my_tiny_mce_before_init( $in ) {
// customize the buttons
$in['theme_advanced_buttons1'] = 'bold,italic,underline,bullist,numlist,hr,blockquote,link,unlink,justifyleft,justifycenter,justifyright,justifyfull,outdent,indent';
$in['theme_advanced_buttons2'] = 'formatselect,pastetext,pasteword,charmap,undo,redo';
// Debug:
// print_r( $in );
// exit();
// Keep the "kitchen sink" open:
$in[ 'wordpress_adv_hidden' ] = FALSE;
return $in;
}
add_filter( 'tiny_mce_before_init', 'my_tiny_mce_before_init' );