This example shows how to draw something in the canvas when previewing a glyph.

from random import random, randint
from vanilla import CheckBox
from mojo.roboFont import CurrentGlyph
from mojo.subscriber import Subscriber, registerGlyphEditorSubscriber


class BubblesPreview(Subscriber):

    debug = True

    def build(self):
        self.showBubbles = CheckBox((10, 10, -10, 20),
                                    'show bubbles',
                                    value=True,
                                    callback=self.showBubblesCallback)

        self.glyphEditor = self.getGlyphEditor()
        self.glyphEditor.addGlyphEditorSubview(self.showBubbles)

        self.container = self.glyphEditor.extensionContainer(
            identifier="com.roboFont.Bubbles.preview",
            location="preview",
            clear=True
        )
        self.bubblesLayer = self.container.appendBaseSublayer()

    def glyphEditorDidSetGlyph(self, info):
        self.updateBubbles()

    def showBubblesCallback(self, sender):
        self.bubblesLayer.setVisible(sender.get())
        if sender.get():
            self.updateBubbles()

    def updateBubbles(self):
        self.bubblesLayer.clearSublayers()
        glyph = CurrentGlyph()

        # bail out if no glyph
        if glyph is None:
            print('sorry, no glyph!')
            return

        # create bubble (given they have a fixed number, they could be "templated")
        xmin, ymin, xmax, ymax = glyph.bounds
        for ii in range(10):
            for jj in range(10):
                diameter = randint(16, 24)
                self.bubblesLayer.appendOvalSublayer(
                    # random position
                    position=(randint(int(xmin), int(xmax)),
                              randint(int(ymin), int(ymax))),
                    # random size
                    size=(diameter, diameter),
                    # random color, with fixed alpha
                    fillColor=(random(), random(), random(), 0.5),
                )


if __name__ == '__main__':
    registerGlyphEditorSubscriber(BubblesPreview)

Last edited on 15/07/2021