Optional ReadonlyariaAccessible name; falls back to label.
Optional ReadonlydatasetExtra attributes set on every refresh, for state the document does not hold, such as whether the format painter is currently armed.
Optional ReadonlyiconOptional ReadonlyisOptional ReadonlyisReadonlylabelVisible label, used when no icon is given and as the tooltip fallback.
ReadonlynameReadonlyrunevent is the click that triggered the item. Items that distinguish a
double click (its detail is 2) can read it; most ignore it.
Optional ReadonlyshortcutAppended to the tooltip, e.g. "Ctrl+B".
A single toolbar control. Open for extension: register your own items without touching the toolbar implementation (open/closed principle).