specification. @var{pixels} non-@code{nil} means return sizes measured
in pixels, otherwise return sizes measured in the default character size
of @var{frame} (@pxref{Frame Font}). @var{frame} is the frame on which
-the image will be displayed. @var{frame} null or omitted means use the
-selected frame (@pxref{Input Focus}).
+the image will be displayed. @var{frame} @code{nil} or omitted means
+use the selected frame (@pxref{Input Focus}).
@end defun
@defvar max-image-size