-(define-public (stencil-whiteout stil style thickness line-thickness)
- "@var{style} is a symbol that determines the shape of the white
-background. @var{thickness} is how far, as a multiple of
-@var{line-thickness}, the white background extends past the extents
-of stencil @var{stil}. If @var{thickness} has not been specified
-by the user, an appropriate default is chosen based on @var{style}."
+(define*-public (stencil-whiteout stil
+ #:optional style thickness (line-thickness 0.1))
+ "@var{style}, @var{thickness} and @var{line-thickness} are optional
+arguments. If set, @var{style} determines the shape of the white
+background. Given @code{'outline} the white background is produced
+by @code{stencil-whiteout-outline}, given @code{'rounded-box} it is
+produced by @code{stencil-whiteout-box} with rounded corners, given
+other arguments (e.g. @code{'box}) or when unspecified it defaults to
+@code{stencil-whiteout-box} with square corners. If @var{thickness} is
+specified it determines how far, as a multiple of @var{line-thickness},
+the white background extends past the extents of stencil @var{stil}. If
+@var{thickness} has not been specified, an appropriate default is chosen
+based on @var{style}."