return value for the x coordinate of the first point, or NULL
return value for the y coordinate of the first point, or NULL
return value for the x coordinate of the second point, or NULL
return value for the y coordinate of the second point, or NULL
CAIRO_STATUS_SUCCESS, or CAIRO_STATUS_PATTERN_TYPE_MISMATCH if pattern is not a linear gradient pattern.
Gets the gradient endpoints for a linear gradient. Since 1.4