show the current glyph's mark color in robofont's glyph window

markcolor-in-glyphoverlayview.py

from vanilla import *
import mojo.drawingTools as ctx
from mojo.events import addObserver, removeObserver
from mojo.canvas import CanvasGroup
from mojo.UI import CurrentGlyphWindow

s = 50

class MarkyGlyph(object):

    def __init__(self):
        self.markview = None
        addObserver(self, "observerGlyphWindowWillOpen", "glyphWindowWillOpen")
        addObserver(self, "observerDraw", "draw")
        addObserver(self, "observerDrawPreview", "drawPreview")

    def observerGlyphWindowWillOpen(self, notification):
        self.window = notification["window"]
        self.markview = CanvasGroup((-s, 0, s, s), delegate=self)
        self.window.addGlyphEditorSubview(self.markview)

    def observerDraw(self, notification):
        if self.markview:
            self.markview.show(True)

    def observerDrawPreview(self, notification):
        # hide the view in Preview mode
        if self.markview:
            self.markview.show(False)

    # canvas delegate callbacks
    def opaque(self):
        return False
    def acceptsFirstResponder(self):
        return False
    def acceptsMouseMoved(self):
        return True
    def becomeFirstResponder(self):
        return False
    def resignFirstResponder(self):
        return False
    def shouldDrawBackground(self):
        return False

    def draw(self):
        glyph = self.window.getGlyph()
        if glyph is None:
            return
        if glyph.markColor:
            r = glyph.markColor.r
            g = glyph.markColor.g
            b = glyph.markColor.b
            a = glyph.markColor.a
        else:
            r = g = b = 1
            a = .1

        x, y, w, h = self.window.getVisibleRect()
        ctx.fill(r,g,b,a)
        ctx.stroke(None)
        ctx.newPath()
        ctx.moveTo((x+s, y+s))
        ctx.lineTo((x+s, y))
        ctx.lineTo((x, y+s))
        ctx.closePath()
        ctx.drawPath()
        ctx.fill(None)

MarkyGlyph()

Oh, that's easier!