x coordinate for the center of the start circle
y coordinate for the center of the start circle
radius of the start circle
x coordinate for the center of the end circle
y coordinate for the center of the end circle
radius of the end circle
the newly created cairo_pattern_t if successful, or an error pattern in case of no memory. The caller owns the returned object and should call cairo_pattern_destroy() when finished with it. 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 cairo_pattern_status().
Creates a new radial gradient cairo_pattern_t 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 cairo_pattern_add_color_stop_rgb() or cairo_pattern_add_color_stop_rgba(). Note: The coordinates here are in pattern space. For a new pattern, pattern space is identical to user space, but the relationship between the spaces can be changed with cairo_pattern_set_matrix().