glyphWindow.getGlyph() returns defcon object.
I want to use it like an RGlyph (the method which usually uses RGlyph as a parameter, in some cases has to glyphWindow.getGlyph()) to access the points. Like this:

from mojo.UI import AllGlyphWindows
for glyphWindow in AllGlyphWindows():
   glyphWindow.getGlyph()[0].points # throws error, because it doesn't have points attr, and RFont does

Is there a way to get RFont out of Defcon object? or to treat defcon glyph like fontParts glyph object?
Or you think that I should create another method for defcon objects than for RFont that does the same thing? (I guess making more methods can cause more troubles with the debugging in the future)

you can wrap an RGlyph around a defcon glyph, like this:

for glyphWindow in AllGlyphWindows():
    # get RGlyph from defcon glyph
    g = RGlyph(glyphWindow.getGlyph())
    # do stuff using the FontParts API
    print(g[0].points)

succes!