Glyphs.app: Guideline through Selected Nodes

#MenuTitle: Guideline through Selected Nodes
# -*- coding: utf-8 -*-
"""Creates a guideline through the currently selected two nodes."""

import GlyphsApp
import math

Font = Glyphs.font
thisLayer = Font.selectedLayers[0]
selection = thisLayer.selection()

if len( selection ) == 2:
    firstPoint = selection[0]
    secondPoint = selection[1]
    xDiff = firstPoint.x - secondPoint.x

    myGuideline = GSGuideLine()
    myGuideline.position = NSPoint( firstPoint.x, firstPoint.y )

    if xDiff != 0.0:
        tangens = (firstPoint.y - secondPoint.y) / xDiff
        myGuideline.angle = math.atan( tangens ) * 180.0 / math.pi
    else:
        myGuideline.angle = 90

    thisLayer.addGuideLine_( myGuideline )
    thisLayer.setSelection_(NSMutableArray.arrayWithObject_(myGuideline))