add_class

Description:

public void add_class (string class_name)

Adds a style class to this, so later uses of the style context will make use of this new class for styling.

Note:

Use [method@Gtk.Widget.add_css_class] instead

In the CSS file format, a `GtkEntry` defining a “search” class, would be matched by:

```css entry.search { ... } ```

While any widget defining a “search” class would be matched by: ```css .search { ... } ```

this	a `GtkStyleContext`
class_name	class name to use in styling