-void gradient_render(Surface *sf, int w, int h);
-void gradient_vertical(Surface *sf, int w, int h);
-void gradient_horizontal(Surface *sf, int w, int h);
-void gradient_diagonal(Surface *sf, int w, int h);
-void gradient_crossdiagonal(Surface *sf, int w, int h);
-void gradient_pyramid(Surface *sf, int w, int h);
-void gradient_solid(Appearance *l, int x, int y, int w, int h);
-void highlight(pixel32 *x, pixel32 *y, gboolean raised);