From ad5b9f1271f48d5829421952b91c2e0e77f36dd9 Mon Sep 17 00:00:00 2001
From: Mark Wooding <mdw@distorted.org.uk>
Date: Mon, 7 Sep 2020 16:33:29 +0100
Subject: [PATCH] slowbox.dtx: Typeset and measure unknown boxes.

If you try to set a slow box with an unknown name, it should be typeset
and measured: otherwise bootstrapping is awful.  Do this.
---
 slowbox.dtx | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/slowbox.dtx b/slowbox.dtx
index f4b71a7..a2c3909 100644
--- a/slowbox.dtx
+++ b/slowbox.dtx
@@ -34,7 +34,7 @@
 %<+package>                [2003/08/27 1.0 skipping of slow boxes]
 % \end{meta-comment}
 %
-% \CheckSum{222}
+% \CheckSum{223}
 %% \CharacterTable
 %%  {Upper-case    \A\B\C\D\E\F\G\H\I\J\K\L\M\N\O\P\Q\R\S\T\U\V\W\X\Y\Z
 %%   Lower-case    \a\b\c\d\e\f\g\h\i\j\k\l\m\n\o\p\q\r\s\t\u\v\w\x\y\z
@@ -111,6 +111,10 @@
 % \env{slowbox$*$} environment takes a tag name, just like \env{slowbox}
 % does.
 %
+% However, if \package{slowbox} sees a slow box \<tag> it's not noticed
+% before, it always typesets the box contents, and saves the measurements for
+% later.
+%
 % \DescribeMacro\slowboxbegin
 % \DescribeMacro\slowboxend
 % It's useful to define your own commands environments which create slow
@@ -267,20 +271,21 @@
   \begingroup%
   \def\sb@end##1{\endgroup}%
   \let\sb@ignore\ignore%
-  \expandafter\sb@hidden\csname sb@box:#1\endcsname{#1}%
+  \expandafter\sb@hidden\csname sb@box:#1\endcsname{#1}{#2}%
 }
 %    \end{macrocode}
 % \end{macro}
 %
 % \begin{macro}{\sb@hidden}
 % We're given the control token and the tag name.  If the control sequence is
-% like |\relax| then |\csname| must have invented it and we just have to make
-% something up.  Otherwise we put the right stuff in a frame.  Don't forget
-% to write out the box dimensions to the new aux file!
+% like |\relax| then |\csname| must have invented it and we should typeset it
+% anyway in order to measure it.  Otherwise we put the right stuff in a
+% frame.  Don't forget to write out the box dimensions to the new aux file!
 %    \begin{macrocode}
-\def\sb@hidden#1#2{%
-  \ifx#1\relax\fbox{Unknown slow box \texttt{#2}!}%
-  \else\edef\next@{\noexpand\sb@hidden@i#1{#2}}\expandafter\next@\fi%
+\def\sb@hidden#1#2#3{%
+  \ifx#1\relax\def\next@{\endgroup\sb@begin@show{#2}{#3}}%
+  \else\edef\next@{\noexpand\sb@hidden@i#1{#2}}\fi%
+  \next@%
 }
 \def\sb@hidden@i#1#2#3#4{%
   \frameonly{#1}{#2}{#3}{Omitted \texttt{#4}}%
-- 
2.11.0