KeySetter

This class represents a modifier that sets a Key (e.g. an attribute or a style) to a specific value on a El. action is what performs this change.

These modifiers are not only idempotent, but are also expected to be undoable, that is, calling key := value2 will override key := value1. In contrast, that is not the case for cls := "class" for example, which adds a class instead of setting it. Such cls modifiers are CompositeKeySetter, which does not extend KeySetter. // #TODO the naming of these traits is confusing...