How to format subsection title (without packages)?

Question

I'd like to change the format for \subsection{} without using special packages. On report.cls we find its definition

\newcommand\subsection{\@startsection{subsection}{2}{\z@}%
                                     {-3.25ex\@plus -1ex \@minus -.2ex}%
                                     {1.5ex \@plus .2ex}%
                                     {\normalfont\large\bfseries}}

But I'd like to use different fonts for the counter and for the title.

For example, for the \section{} command I'm using

{\fontsectionnumber{\color{black!50}\thesection.}\hspace{.5em}{\fontsection\MakeUppercase{#1}}} 

How to do the same for \subsection?

---

Edit: here is the adapted code for \section{}.

\newcommand\section{\global\@topnum\z@
                      \@afterindenttrue
                      \secdef\@section\@ssection}
\def\@section[#1]#2{\ifnum \c@secnumdepth >\z@
                       \if@mainmatter
                         \refstepcounter{section}%
                         \typeout{\thesection}%
                         \addcontentsline{toc}{section}%
                         {\protect{\color{black!30} %
                         {\fontsectionnumbertoc\numberline{\thesection.}}} {\normalfont #1} \hspace{1em} %
                         {\fontheadernumber\thepage}\hfil}%
                       \else
                         \addcontentsline{toc}{section}{#1}%
                       \fi
                    \else
                      \addcontentsline{toc}{section}{#1}%
                    \fi
                    \sectionmark{#1}%
                    \addtocontents{lof}{\protect\addvspace{10\p@}}%
                    \addtocontents{lot}{\protect\addvspace{10\p@}}%
%                    \if@twocolumn
%                      \@topnewpage[\@makechapterhead{#2}]%
%                    \else
                      \@makesectionhead{#2}%
                      \@afterheading
                    }
\def\@makesectionhead#1{%
  \vskip 5mm
  {\parindent \z@ \raggedright 
    \ifnum \c@secnumdepth >\m@ne
      %\if@mainmatter
        {\fontsectionnumber{\color{black!50}\thesection.}\hspace{.5em}{\fontsection\MakeUppercase{#1}}} 
        %\newline\nobreak
%        \vskip 0\p@
      %\fi
    \fi
    \interlinepenalty\@M
%    \large\MakeUppercase{#1} \par\nobreak
    \vskip 2mm %2.3ex \@plus.2ex
  }}

Answer 1

The standard way to cope with this kind of problems is to use \@seccntformat, the macro that takes care of formatting the section number (any level below chapter, in the standard classes).

The usual definition is

\csname the#1\endcsname \quad

where #1 is the counter associated to the current section level. So if you define

\def\@seccntformat#1{%
  {\csname font#1number\endcsname\csname the#1\endcsname}\quad}

you can obtain any effect you prefer.

If you don't define \font<level>number, the command would be the same as \relax, so it won't raise errors.

Example.

\documentclass{article}
\usepackage[T1]{fontenc}
\usepackage{lipsum}

\def\fontsectionnumber{\fontsize{9}{16}\usefont{T1}{DejaVuSans-TLF}{b}{n}}
\def\fontsection{\fontsize{9}{16}\usefont{T1}{DejaVuSans-TLF}{m}{n}}
\def\fontsubsectionnumber{\fontsize{7}{12}\usefont{T1}{DejaVuSans-TLF}{b}{n}}
\def\fontsubsection{\fontsize{7}{12}\usefont{T1}{DejaVuSans-TLF}{m}{n}}

\makeatletter

\def\@seccntformat#1{%
  {\csname font#1number\endcsname\csname the#1\endcsname}\quad}

\renewcommand\section{%
  \@startsection{section}{1}{\z@}%
    {-3.5ex \@plus -1ex \@minus -.2ex}%
    {2.3ex \@plus.2ex}%
    {\normalfont\fontsection}}

\renewcommand\subsection{%
  \@startsection{subsection}{2}{\z@}%
    {-3.25ex\@plus -1ex \@minus -.2ex}%
    {1.5ex \@plus .2ex}%
    {\normalfont\fontsubsection}}

\makeatother

\begin{document}

\section{This is a section title}

\lipsum[2]

\subsection{This is a subsection title}

\lipsum[3]

\end{document}