Show master in the Preview Field or Window

Show master.py

#MenuTitle: Show master
# -*- coding: utf-8 -*-
__doc__="""
Show the amster in preview field or preview window.
"""

import GlyphsApp
from Foundation import NSApplication

numberOfInstances = len( Glyphs.font.instances )
Doc = Glyphs.currentDocument
PreviewField = Doc.windowController().activeEditViewController()
PreviewPanel = None
 
for p in NSApplication.sharedApplication().delegate().valueForKey_("pluginInstances"):
	if p.__class__.__name__ == "NSKVONotifying_GlyphsPreviewPanel":
		PreviewPanel = p

try:
	currentInstanceNumber = PreviewField.selectedInstance()

	if currentInstanceNumber < numberOfInstances:
		PreviewField.setSelectedInstance_( 0 )
		if PreviewPanel:
			PreviewPanel.setSelectedInstance_( 0 )
	else:
		PreviewField.setSelectedInstance_( 0 )
		if PreviewPanel:
			PreviewPanel.setSelectedInstance_( 0 )

except Exception, e:
	print "Error:", e