Unpredictable Vertical Spaces

Question

I'm writing up a résumé, and I am very particular about making sure that each section is separated by the exact-right-looking amount of spacing. My sections are divided with an \hrule (although in my real document I use the titlesec package to define their format). The rule makes it easy to notice when one section's spacing is different from another's.

The following example shows several of the elements that I need in my document. I have placed the rules very close to the text, to make the difference even more obvious. Depending on whether a section contains text or a list or columns, the subsequent section gets spaced an irregular amount below it. Edit: I've used \myrule instead of \hrule and followed other suggestions already given by @Ulrike.

\documentclass[10pt]{article}

\usepackage[letterpaper,margin=1in]{geometry}
\usepackage{enumitem}
\usepackage{multicol}

\newcommand{\sampletext}{Here is some sample text\strut}

\newcommand{\myrule}{\par\vspace{-1\baselineskip}\noindent\strut\rule{\textwidth}{0.4pt}}

\newenvironment{compactlist}%
    {\begin{itemize}[topsep=0pt,itemsep=0pt,parsep=0pt,labelindent=0em,partopsep=0pt,leftmargin=*]}
    {\end{itemize}}

\begin{document}

\section{Plain}
\sampletext
\myrule

\section{Itemized}
\begin{compactlist}
    \item \sampletext
    \item \sampletext
\end{compactlist}
\myrule

\section{Itemized With Text}
\noindent\sampletext
\begin{compactlist}
    \item \sampletext
    \item \sampletext
\end{compactlist}
\myrule

\section{Parbox Itemized}
\hbox{
    \parbox[t]{7in}{
        \begin{compactlist}
            \item \sampletext
            \item \sampletext
        \end{compactlist}
    }
}
\myrule

\section{Parbox Itemized With Text}
\parbox[t]{6.5in}{
    \sampletext
    \begin{compactlist}
        \item \sampletext
        \item \sampletext
    \end{compactlist}
}
\myrule

\section{Multicols}
\setlength{\multicolsep}{0pt}
\begin{multicols}{3}
    \begin{compactlist}
        \item \sampletext
        \item \sampletext
        \item \sampletext
        \item \sampletext
        \item \sampletext
        \item \sampletext
    \end{compactlist}
\end{multicols}
\myrule

\end{document}

Is there any way to enforce consistent vertical spacing?

Answer 1

As requested here my comments as answer:

I wouldn't use the primitive \hrule but a \myrule defined e.g. like this: \newcommand\myrule{\par\noindent\strut\rule{\textwidth}{0.4pt}}.

The spacing is then more consistent that with \hrule. You can further improve it by using partopsep=0pt in your list definition. It could also be sensible to add a \strut to the sample text.

The 1pt below the \parbox is the line skip. The parbox is to the eyes of TeX like a character with a very large descender. So TeX inserts \lineskip (default 1pt) to avoid that it touches the next line. You can get rid of it with \lineskip=0pt (unless your \parbox contains some unusual objects with large descender in the last line). You shouldn't remove the \strut.