enum MetaGradientType

typedef enum {
  META_GRADIENT_VERTICAL,
  META_GRADIENT_HORIZONTAL,
  META_GRADIENT_DIAGONAL,
  META_GRADIENT_LAST
} MetaGradientType;

meta_gradient_create_simple ()

GdkPixbuf *         meta_gradient_create_simple         (int width,
                                                         int height,
                                                         const GdkRGBA *from,
                                                         const GdkRGBA *to,
                                                         MetaGradientType style);

meta_gradient_create_multi ()

GdkPixbuf *         meta_gradient_create_multi          (int width,
                                                         int height,
                                                         const GdkRGBA *colors,
                                                         int n_colors,
                                                         MetaGradientType style);

meta_gradient_create_interwoven ()

GdkPixbuf *         meta_gradient_create_interwoven     (int width,
                                                         int height,
                                                         const GdkRGBA colors1[2],
                                                         int thickness1,
                                                         const GdkRGBA colors2[2],
                                                         int thickness2);

Interwoven essentially means we have two vertical gradients, cut into horizontal strips of the given thickness, and then the strips are alternated. I'm not sure what it's good for, just copied since WindowMaker had it.

meta_gradient_add_alpha ()

void                meta_gradient_add_alpha             (GdkPixbuf *pixbuf,
                                                         const guchar *alphas,
                                                         int n_alphas,
                                                         MetaGradientType type);