snippet_normalize (cr, width, height)

pattern = cairo.LinearGradient (0, 0, 1, 1)
pattern.add_color_stop_rgb (0, 0, 0.3, 0.8)
pattern.add_color_stop_rgb (1, 0, 0.8, 0.3)

mask = cairo.RadialGradient (0.5, 0.5, 0.25, 0.5, 0.5, 0.5)
mask.add_color_stop_rgba (0, 0, 0, 0, 1)
mask.add_color_stop_rgba (0.5, 0, 0, 0, 0)

cr.set_source (pattern)
cr.mask (mask)