Gets the metrics for a CairoScaledFont.
CairoScaledFont
cairoScaledFontExtents(scaled.font)
scaled.font
[CairoScaledFont] a CairoScaledFont
A list containing the following elements:
extents
[CairoFontExtents] a CairoFontExtents which to store the retrieved extents.
CairoFontExtents
Derived by RGtkGen from GTK+ documentation