Getting \needspace to work in multicols

Question

I have code that generates multiple lists of data in the form of XeLaTeX source. Because the lines of data are very short, I'm presenting it in a multicols environment. Each list has a few headings in it. Occasionally the list of data is very short – just a single heading and one line of data – and in this case, I'm struggling to prevent the heading and following line from being split across columns. Here's a MWE showing the problem and my attempt to fix it using \needspace:

\documentclass[a4paper]{article}
\usepackage{multicol}
\usepackage{needspace}
\newcommand{\tblheading}[1]{\needspace{2\baselineskip}\textbf{#1}\newline}
\begin{document}
\begin{multicols}{3}
\tblheading{Heading}
Entry
\end{multicols}
\end{document}

I've tried using \Needspace* instead of \needspace, I've also tried adding \raggedcolumns, increasing the requested space from 2\baselineskip, and using \par, \\ or \\* instead of \newline, but whatever I try, I cannot prevent these two lines from being split between two columns. Can anyone help?

(I know that in principle I could use a minipage or perhaps samepage environment, but I don't think that's possible here because I really need to keep the special handling within the \tblheading macro due to the way the data is generated.)

Answer 1

The \minisec command of KOMA does more or less this:

\documentclass[a4paper]{article}
\usepackage{multicol}
\makeatletter
\newcommand\minisec[1]{%
    \if@noskipsec \leavevmode \fi
    \par
    \@afterindentfalse
    \if@nobreak
      \everypar{}%
    \else
      \addpenalty\@secpenalty\addvspace{1.5ex}% space before, adjust if needed
    \fi
  {\parindent \z@
   \setlength{\parfillskip}{\z@ plus 1fil}
    \normalfont\bfseries
    \nobreak\interlinepenalty \@M #1\par\nobreak%
  }\nobreak
  \@afterheading
}                              
\makeatother
\begin{document}
\begin{multicols}{3}
\minisec{Heading}
Entry
\end{multicols}
\end{document}

Answer 2

Multicol actually formats the entire page as a single column, then splits it into two or more equal lengths. It turns out that \@afterheading will not prevent this split from taking place, so \subsection* etc won't work either. My old version of \needspace will work, fortunately.

\documentclass[a4paper]{article}
\usepackage{multicol}
\setlength\columnseprule{.4pt}
\usepackage{lipsum}

\makeatletter
\newcommand{\tblheading}[1]{\par\rule{0pt}{\dimexpr 2\baselineskip-\dp\strutbox}\vspace{-2\baselineskip}\newline
  \indent\textbf{#1}\newline}
\makeatother

\begin{document}
\begin{multicols}{3}
\noindent\rule{\columnwidth}{49\baselineskip}% 48 will go in first column

\tblheading{Heading}
Entry

\lipsum[1-4]
\end{multicols}
\end{document}