Gets the surface of a surface pattern. The reference returned
is owned by the pattern; the caller should call
csurface:Reference() if the surface is to be retained.
This function also returns #CAIRO_STATUS_SUCCESS, or
#CAIRO_STATUS_PATTERN_TYPE_MISMATCH if the pattern is not a surface
pattern.
Inputs
none
Results
status
#CAIRO_STATUS_SUCCESS or #CAIRO_STATUS_PATTERN_TYPE_MISMATCH