fbox drawn incorrectly after \noindent

Question

What's going on here that the first and last \fbox are not getting drawn correctly when immediately following \noindent?

\documentclass{article}
\usepackage{pst-node}
\pagestyle{empty}
\begin{document}

\noindent\fbox{A\rule{0.4pt}{3ex}}

\fbox{A\rule{0.4pt}{3ex}}


\noindent\fbox{A}

\fbox{A}

\noindent%
\begin{pspicture}(0,0)
    \psset{linecolor=red,linewidth=0.4pt}
    \rput(1.45em,6.5\baselineskip){\cnode{0.05}{A}}
    \rput(2.9em,1.84\baselineskip){\cnode{0.05}{B}}

\end{pspicture}
\end{document}

It's barely noticeable: but now that I see it, it annoys me.

Answer 1

It is an rounding error of dvips:

543 575 a % moveto
Fa(A)p % draw `A'
605 575 4 108 v % x y width height rule
515 443 123 4 v % x y width height rule % horizontal rule
515 602 4 161 v % x y width height rule % left vertical rule
633 602 V % x y (previous width) (previous height) rule % right vertical rule
515 604 123 4 v % x y width height rule % horizontal rule

The horizontal rules start at 515 with width 123 to 638. The rule thickness is 4, thus the right vertical rule should start at 634. but it is starting at 633.

You can use a higher resolution to get a more accurate result, e.g.

dvips -D8000

or better

dvips -Ppdf

that uses -D8000 and also includes the header alt-rule.pro:

%%BeginProcSet: alt-rule.pro 0 0
%!
% Patch by TVZ
% Makes dvips files draw rules with stroke rather than fill.
% Makes narrow rules more predictable at low resolutions
% after distilling to PDF.
% May have unknown consequences for very thick rules.
% Tested only with dvips 5.85(k).
[...]

Result with dvips -Ppdf: