ACM acmart sigplan: single-column draft mode with margin notes

singlecolumn-sigplan.tex

% =============================================================
% ACM acmart sigplan: single-column draft mode with margin notes
% =============================================================
%
% Problem: acmart's sigplan format hardcodes twocolumn mode.
% There's no clean way to get single-column output while
% preserving sigplan formatting (fonts, headings, citations).
%
% This hack:
%   1. Hijacks \twocolumn so \maketitle stays single-column
%   2. Sets text width to one sigplan column (~3.33in)
%   3. Uses remaining space for todonotes margin notes
%   4. Disables twoside margin switching (notes always on right)
%
% Usage: wrap in \ifdraft or similar conditional.
% Requires: \usepackage{geometry}, \usepackage{todonotes}

% --- In preamble (inside \ifdraft) ---
\usepackage{geometry}
\usepackage{todonotes}

% --- After \begin{document}, INSTEAD of bare \maketitle ---

% Hijack \twocolumn to prevent \maketitle from enabling twocolumn
\makeatletter
\let\origtwocolumn\twocolumn
\renewcommand{\twocolumn}[1][]{\vbox{#1}\@twocolumnfalse}
\makeatother

\maketitle

% Restore \twocolumn and set single-column geometry
\makeatletter
\let\twocolumn\origtwocolumn
\makeatother
\setlength{\textwidth}{3.33in}       % sigplan column width
\setlength{\hsize}{3.33in}
\setlength{\columnwidth}{3.33in}
\setlength{\linewidth}{3.33in}
\setlength{\marginparwidth}{3.33in}  % wide margin for todonotes
\setlength{\marginparsep}{24pt}      % matches sigplan columnsep

% Force margin notes to right side on all pages
\makeatletter\@twosidefalse\@mparswitchfalse\makeatother

% Fix extra gap between title and first section
\vspace{-\baselineskip}