PangoLayoutLine onto a GdkDrawable, overriding the
layout's normal colors with foreground and/or background.
foreground and background need not be allocated.gdkDrawLayoutLineWithColors(drawable, gc, x, y, line, foreground, background)PangoContext has a transformation matrix set, then
x and y specify the position of the left edge of the baseline
(left is in before-tranform user coordinates) in after-transform
device coordinates.