When Annotator creates a toolbar, it iterates a list of registered custom mark edit controllers and gets a ToolbarInfo property for each. ToolbarInfo is a read-only edit controller’s property of public type ImGearARTFormsToolbarButtonInfo.
This class has fields that are necessary for creating a toolbar button which will be associated to custom mark/edit controller. In user’s overridden ToolbarInfo property the user must create a new ImGearARTFormsToolbarButtonInfo object and fill its fields with the button’s icon, tooltip string and user type identifier (string, same as was used when the controller is registered).