What is Causing This Phenomenon? Is it the Geometry Package?

Question

Consider the code

\documentclass[border=0pt]{book}
\usepackage[paperwidth=5.625in,paperheight=0.125in]{geometry}
%\paperwidth=5.625in \paperheight=0.125in
\usepackage{xcolor}

\pagecolor{red}
\begin{document}
    \pagestyle{empty}
    \par \emph{ }
\end{document}

which produces

Should not only one of these colored rectangles appear?---for, if I replace \usepackage[paperwidth=5.625in,paperheight=0.125in]{geometry} with \paperwidth=5.625in \paperheight=0.125in and run the code

\documentclass[border=0pt]{book}
%\usepackage[paperwidth=5.625in,paperheight=0.125in]{geometry}
\paperwidth=5.625in \paperheight=0.125in
\usepackage{xcolor}

\pagecolor{red}
\begin{document}
    \pagestyle{empty}
    \par \emph{ }
\end{document}

I get what is expected:

QUESTION: Is it the geometry package which is producing this occurrence? What code should I be using in order to produce a color-filled rectangle (in this case) of dimensions 5.625" x 0.125"?

For reasons related to the nature of the project I am working on, I compile this code with xelatex.

Thank you.

Answer 1

You could use the standalone class and output a box of that size:

\documentclass[]{standalone}

\usepackage{xcolor}

\begin{document}
\textcolor{red}{\rule{5.625in}{0.125in}}
\end{document}

Answer 2

Your manual settings of \paperwidth and \paperheight do not change the size of the text area or the margins. The text area is just outside the specified paper size. You would see this, if you would add some text, e.g. \emph{Text} instead of \emph{}, because you won't see the text. geometry on the other hand tries to also set the text area. But because the paper height is too low, the height of text area is also too low (less than \baselineskip + \topskip) and also the margins + the height of the text area > \paperheight. This results in underfull and overfull \vboxes and also in several page breaks. Even for an empty document the too low \textheight results in two pages:

\documentclass{book}
\usepackage[paperwidth=5.625in,paperheight=0.125in]{geometry}
%\paperwidth=5.625in \paperheight=0.125in
\usepackage{xcolor}

\pagecolor{red}
\pagestyle{empty}
\begin{document}
\end{document}

You can compare the values also from within the information geometry writes to the log:

\documentclass{book}
\usepackage[pass]{geometry}% don't change anything
%\usepackage[paperwidth=5.625in,paperheight=0.125in,nohead,nofoot,margin=0pt]{geometry}
\paperwidth=5.625in \paperheight=0.125in
\usepackage{xcolor}

\pagecolor{red}
\pagestyle{empty}
\begin{document}
\end{document}

results in

* \paperwidth=406.51874pt
* \paperheight=9.03374pt
* \textwidth=345.0pt
* \textheight=550.0pt
* \oddsidemargin=35.0pt
* \evensidemargin=89.0pt
* \topmargin=22.0pt
* \headheight=12.0pt
* \headsep=18.06749pt
* \topskip=10.0pt
* \footskip=25.29494pt
* \marginparwidth=125.0pt
* \marginparsep=7.0pt
* \columnsep=10.0pt
* \skip\footins=9.0pt plus 4.0pt minus 2.0pt
* \hoffset=0.0pt
* \voffset=0.0pt
* \mag=1000
* \@twocolumnfalse
* \@twosidetrue
* \@mparswitchtrue
* \@reversemarginfalse
* (1in=72.27pt=25.4mm, 1cm=28.453pt)

but

\documentclass{book}
\usepackage[paperwidth=5.625in,paperheight=0.125in]{geometry}
%\paperwidth=5.625in \paperheight=0.125in
\usepackage{xcolor}

\pagecolor{red}
\pagestyle{empty}
\begin{document}
\end{document}

results in

* layout: <same size as paper>
* layoutoffset:(h,v)=(0.0pt,0.0pt)
* modes: twoside 
* h-part:(L,W,R)=(48.78275pt, 284.56187pt, 73.17412pt)
* v-part:(T,H,B)=(1.08405pt, 6.32358pt, 1.62611pt)
* \paperwidth=406.51874pt
* \paperheight=9.03374pt
* \textwidth=284.56187pt
* \textheight=6.32358pt
* \oddsidemargin=-23.48724pt
* \evensidemargin=0.90413pt
* \topmargin=-101.25343pt
* \headheight=12.0pt
* \headsep=18.06749pt
* \topskip=10.0pt
* \footskip=25.29494pt
* \marginparwidth=125.0pt
* \marginparsep=7.0pt
* \columnsep=10.0pt
* \skip\footins=9.0pt plus 4.0pt minus 2.0pt
* \hoffset=0.0pt
* \voffset=0.0pt
* \mag=1000
* \@twocolumnfalse
* \@twosidetrue
* \@mparswitchtrue
* \@reversemarginfalse
* (1in=72.27pt=25.4mm, 1cm=28.453pt)