The example script below shows how to add a custom button to the toolbar of the Font Overview by subclassing the Subscriber class and defining the fontDocumentWantsToolbarItems callback.

The gear icon is selected from macOS system icons using NSImageName.

from AppKit import NSImageNameAdvanced
from mojo.subscriber import Subscriber, registerRoboFontSubscriber

class AddToolbarItem(Subscriber):
    debug = True

    def fontDocumentWantsToolbarItems(self, info):
        # create the button
        newItem = {'itemIdentifier': 'MyButton',
                   'label':          'My Button',
                   'toolTip':        'My Button',
                   'imageNamed':      NSImageNameAdvanced,
                   'callback':        self.customButton}

        # add it to the toolbar
        info['itemDescriptions'].insert(2, newItem)

    def customButton(self, sender):

if __name__ == '__main__':

Last edited on 01/09/2021