DowncastAttributeEvent

Fired in the following cases:

• when an attribute has been added, changed, or removed from a node,
• when a node with an attribute is inserted,
• when a collapsed model selection attribute is converted.

attribute is a namespace for a class of events. Names of actually called events follow this pattern: attribute:attributeKey:name. attributeKey is the key of added/changed/removed attribute. name is either '$text' if change was on a text node, or the name of element which attribute has changed.

This way listeners can either listen to a general attribute:bold event or specific event (for example attribute:src:imageBlock).