The teeny_mce_buttons filter allows you to add or remove buttons from the teeny mce buttons row used in Press This.

It is evaluated in the _WP_Editors::editor_settings() method in the wp-includes/class-wp-editor.phpv file. The _WP_Editors class is publicly instantiated via wp_editor().

Please note: Adding a button via teeny_mce_buttons will only register the button. In order to implement functionality for it, take a look at the teeny_mce_plugins filter in the same file.

Example:

The following example registers a new button in the teeny mce buttons row.