CairoPattern between the two
circles defined by (cx0, cy0, radius0) and (cx1, cy1, radius1). Before using the
gradient pattern, a number of color stops should be defined using
cairoPatternAddColorStopRgb or
cairoPatternAddColorStopRgba.cairoPatternCreateRadial(cx0, cy0, radius0, cx1, cy1, radius1)CairoPattern] the newly created CairoPattern if successful, or
an error pattern in case of no memory.This function will always return a valid pointer, but if an error
occurred the pattern status will be set to an error. To inspect
the status of a pattern use cairoPatternStatus.
cairoPatternSetMatrix.