[Tex/LaTex] In fancyhdr, ensure every letters in chapter/title names are in lowercase

Question

In designing novels, (Document-class Book KOMA SCRIPT) I prefer to use all-small-caps in the running heads. Please find the first example, where both howards end and chapter 29 were all set in lowercase and old style numerals. I achieved this through \nouppercase and literally converted the necessary letters to lowercase, it looks tidy, has the small caps spacing between letters and good proportion with old style numerals.

i.e.

\fancyhead[EC]{\rmfamily \sc \small \nouppercase howards end}

However, in some design, normal title-caps are required for bookmarks and chapter title lettering. For instance, in Back to Methuselah, the chapter name needs to be set as The Things Happens with title caps. Here I cheated by setting them all in CAPs, so it looks tidy.

\fancyhead[OC]{\rmfamily \bf  \small \sc \leftmark }

Of course, setting all uppercase lost the lovely spacing that smallcaps will normally have and also the proportion with the old style numerals.

So here is my question, is there a way to stoutly make sure all the letters in headings are in lowercase even they came in as mix caps?

Here is the minimal example:

I'm using LyX, but the principle and code should be the same:

Load fancyhdr in document class Book KOMA-Script two side document. all other default.

\fancyhead{}
\fancyfoot{}

\fancyhead[OC]{\rmfamily \small \nouppercase \leftmark}

Dummy text with chapter name This is Mixing Caps will produce the following example, but I want them to be this is mixing caps in the header only so that I can apply small caps on.

Answer 1

Here's a way:

\documentclass{scrbook}
\usepackage[osf]{mathpazo} % a font with old style figures

\usepackage{fancyhdr,textcase}

\pagestyle{fancy}
\renewcommand{\chaptermark}[1]{\markboth{#1}{}}
\renewcommand{\headrulewidth}{0pt}
\fancyhf{}
\fancyhead[LE,RO]{\footnotesize\scshape\thepage}
\fancyhead[CE]{\scshape\MakeTextLowercase{\leftmark}}
\fancyhead[CO]{\scshape\MakeTextLowercase{\chaptername~\thechapter}}