[cairo] Some Pango Text Attributes have no effect

[Stefan Salewski]

It seems that on my Linux box, Gentoo AMD64, default fonts sans (I think
it is Bitstream Vera), some Pango attributes have no effect.

All works for foreground and background color,  Strikethrough,
Underline. But AttrVariant or AttrStretch seems to have no effect.
Yesterday I made some tests with my own Ruby code, drawing to a cairo
surface. Now I have tested the tutorial from 
http://zetcode.com/tutorials/pygtktutorial/pango/

by replacing (working) AttrUnderline and  AttrStrikethrough with
AttrVariant and AttrStretch. Again, no visible effect.

fg_color = pango.AttrForeground(65535, 0, 0, 0, 6)
#underline = pango.AttrUnderline(pango.UNDERLINE_DOUBLE, 7, 11)
underline = pango.AttrVariant(pango.VARIANT_SMALL_CAPS, 7, 11)
bg_color = pango.AttrBackground(40000, 40000, 40000, 12, 19)
#strike = pango.AttrStrikethrough(True, 20, 29)
strike = pango.AttrStretch(pango.STRETCH_EXPANDED, 20, 29)

This is no problem, because I do not really need that attributes, but it
would be good to know the reason. Is this still an unimplemented feature
of Pango, or have the fonts to support these attributes, and my fonts do
not.

Best regards

Stefan Salewski