Section Styles: Spacing, Font and Paragraph-Indentation

Question

I am using sectsty to configure my section styles. I have read that perhaps titlesec is more powerful. A solution to my question below using titlesec is completely satisfactory.

Currently I am setting the fonts for section and subsection as follows.

\sectionfont{%                      % Change font of \section command
    \noindent
    \usefont{OT1}{phv}{b}{n}%       % bch-b-n: CharterBT-Bold font
    \sectionrule{0pt}{0pt}{-5pt}{2pt}}
\subsectionfont{\noindent\usefont{OT1}{phv}{b}{n}}

I am then adjusting the spacing as follows.

\renewcommand\section{\@startsection{section}{1}{\z@}%
    {\bigskipamount}%
    {\bigskipamount}%
    {\normalfont\large\bfseries\SS@sectfont}}
\renewcommand\subsection{\@startsection{subsection}{2}{\z@}%
    {\bigskipamount}%
    {\medskipamount}%
    {\normalfont\normalsize\bfseries\SS@subsectfont}}

The template for this adjustment comes from this SE question: How to adjust the title spacing using sectsty package. A somewhat equivalent template for titlesec can be found from this SE question: Reducing spacing after headings.

Now my issue is the following. When I do this \renewcommand\section..., the first paragraph is indented. I don't want this. With titlesec, one can add an option noindentafter to the package call or use \titlespacing* to remove this indentation. See this SE question: Cancelling first-line indents after section titles. I cannot find similar things for sectsty, nor has experimentation succeeded.

Why am I using sectsty then? Well, I like the font and sectionrule options. I have not been able to get the same font using titlesec and the \titleformat option---which is somewhat confusing to me. The command \sectionrule appears to be specific to sectsty.

Thus I would like one of the following solutions.

1. Obtain the same font and section rule using titlesec.
2. Remove the indentation using sectsty.

Option (1) would be preferable, but Option (2) is acceptable.

---

Two MWEs. The first is set up for sectsty and the second for titlesec.

\documentclass[]{article}
\usepackage{sectsty}
\sectionfont{%                      % Change font of \section command
    \noindent
    \usefont{OT1}{phv}{b}{n}%       % bch-b-n: CharterBT-Bold font
    \sectionrule{0pt}{0pt}{-5pt}{2pt}}
\subsectionfont{\noindent\usefont{OT1}{phv}{b}{n}}
\begin{document}
\section{Section Title}
This is not indented
\makeatletter
\renewcommand\section{@startsection{section} {1}{\z@}%
    {\bigskipamount}%
    {\bigskipamount}%
    {\normalfont\large\bfseries\SS@sectfont}}
\makeatother
\section{Next Section}
This is indented now \texttt{:frowning:}
\end{document}

\documentclass[]{article}

\usepackage{titlesec}
\titleformat{\section}
    {\sffamily \normalsize \bfseries \usefont{OT1}{phv}{b}{n}}{\thesection}{1em}{}

\begin{document}

\section{Section Title}
This is not indented

\titlespacing{\section}
    {0pt}
    {\bigskipamount}
    {\medskipamount}
\section{Next Section}
This is indented now \texttt{:frowning:}

\titlespacing*{\section}
    {0pt}
    {\bigskipamount}
    {\medskipamount}
\section{Final Section}
But viola, it is no longer indented by adding \texttt{*}

\end{document}

Answer 1

Here a way to do what you want with titlesec. I took the liberty to put \titlespacing in the preamble, to replace the Helvetica font with its clone TeX Gyre Heros, which has more glyphs and to reduce the spacing between section number and title to a half quad, which looks better, from my point of view.

\documentclass[]{article}
\usepackage[noindentafter]{titlesec}
\titleformat{\section}
    {\usefont{T1}{qhv}{b}{n} \normalsize\boldmath}{\thesection}{0.5em}{}[{\titlerule[2pt]}]
\titlespacing{\section}
    {0pt}
    {\bigskipamount}
    {\medskipamount}
\begin{document}
\section{Section Title}
This is not indented
\section{Next Section}%
This is \emph{not} indented now\texttt{:frowning:}
\section{Final Section}
But Viola, it is no longer indented by adding \texttt{*}
\end{document}