Building a custom key observer ↩

• Creating a basic controller object
• Registering the tool with Subscriber
• Adding a callback method
• The Event Info Dictionary
• Observing one key and switching layers
• Setting the script as a start-up script

RoboFont has an interface for defining keyboard shortcuts or “Hot Keys” for menu items, the Short Keys Preferences. With a bit of code, we can also create custom Hot Keys for actions that are not available in the UI.

In this tutorial, we’ll show how to use a Subscriber object to make the Glyph Editor jump to the foreground layer when the f key is pressed.

Creating a basic controller object

We’ll start by subclassing a Subscriber object, using a class definition.

from mojo.subscriber import Subscriber

class JumpToForeground(Subscriber):
    pass


JumpToForeground()

In the above script, a new JumpToForeground class is defined by subclassing a Subscriber object. The class is empty, there is no need to __init__ or build anything in this case, we need no window for this tool.

Registering the tool with Subscriber

Let’s start by registering the tool along with the glyph editor with a function from the subscriber module:

from mojo.subscriber import Subscriber, registerGlyphEditorSubscriber

class JumpToForeground(Subscriber):
    pass


registerGlyphEditorSubscriber(JumpToForeground)

So, we’are not initiating the tool ourselves anymore, but we are passing its name to the registerGlyphEditorSubscriber function. Under the hood, Subscriber will take care of constructing the class when a glyph editor opened and it will assign our tool to the newly opened glyph editor. Our tool will remain alive until the glyph editor is closed. So, we won’t need to stop listening to events once the tool is closed, RoboFont will take care of it for us.

Adding a callback method

from mojo.subscriber import Subscriber, registerGlyphEditorSubscriber

class JumpToForeground(Subscriber):

    debug = True

    def glyphEditorDidKeyDown(self, info):
        print(info)


registerGlyphEditorSubscriber(JumpToForeground)

The Subscriber reference lists all the events that Subscriber can listen. There is one event particularly suited for our case, the glyphEditorDidKeyDown method: this method will be called each time a key is pressed while the glyph editor is active.

The Event Info Dictionary

If you print the event info object in the RoboFont output window, you’ll see quite a rich dictionary with several keys. We are interested in the deviceState dictionary, where we can find which key triggered the callback:

'deviceState': {
    'keyDown': 'f',
    'keyDownWithoutModifiers': 'f',
    'up': False,
    'down': False,
    'left': False,
    'right': False,
    'shiftDown': 0,
    'capLockDown': 0,
    'optionDown': 0,
    'controlDown': 0,
    'commandDown': 0,
    'locationInWindow': <NSPoint x=615.7727661132812 y=626.8971557617188>,
    'locationInView': <NSPoint x=2052.7727661132812 y=2583.8971557617188>,
    'clickCount': 0
    }

Now we can use this information to filter the events and jump to the foreground only when 'f' is pressed.

Observing one key and switching layers

The operations is just a matter of using a conditional statement in combination with the SetCurrentLayerByName method from the mojo.UI module.

from mojo.UI import SetCurrentLayerByName
from mojo.subscriber import Subscriber, registerGlyphEditorSubscriber

class JumpToForeground(Subscriber):

    debug = True

    def glyphEditorDidKeyDown(self, info):
        if info['deviceState']['keyDownWithoutModifiers'] == "f":
            SetCurrentLayerByName("foreground")


registerGlyphEditorSubscriber(JumpToForeground)

Setting the script as a start-up script

And that’s it! Save this script in a place you can keep track of, and from the Extensions Preferences, you can add this as a Start Up Script so that it’s always run one time when RoboFont launches.

• Setting up start-up scripts

Contributed by Andy Clymer, updated by Roberto Arista for RoboFont 4