Actions

widget_css_classes_form

Add extra fields to the widget form.
@param  string  $fields    Current HTML.
@param  array   $instance  The widget instance.
@return string

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widget_css_classes_update

Runs after updating the widget data (before the actual DB update)
@param  array  $instance
@param  array  $new_instance

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widget_css_classes_add_classes

Modify the widget parameters, normally to add extra classes.
@param  array      $params
@param  string     $widget_id
@param  int        $widget_num
@param  array      $widget_opt
@param  WP_Widget  $widget_obj
@return array

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widget_css_classes_settings

Add items fields to the settings page.