A strange behavior of `\magstep0`
Hi LuaTeX Team, I am writing to report strange behavior of the \magstep0 command , or the original magnification \csname @m\endcsname. The problem is happened in a macro with \afterassignment and then assign \magstep0 to a count register. For the LuaTeX version: luatex --version This is LuaTeX, Version 1.22.0 (TeX Live 2026/dev/Arch Linux) Development id: 7674 Execute 'luatex --credits' for credits and version details. There is NO warranty. Redistribution of this software is covered by the terms of the GNU General Public License, version 2 or (at your option) any later version. For more information about these matters, see the file named COPYING and the LuaTeX source. LuaTeX is Copyright 2025 Taco Hoekwater and the LuaTeX Team. The problem is happened in a macro with \afterassignment and then assign \magstep0 to a count register. A shortest description: ``` \newcount\count \def\problemhere#1\relax#2{\string#1#2} \def\todo{ \afterassignment\problemhere \count= } ``` For the above macro, \todo\magstep1{HERE} just print HERE while \todo\magstep0{HERE} print \or1200HERE. It seems that \magstep0 break the \ifcase structure in the \magstep definition, It seems that this is not a expected behavior. Complete use case steps and more details are on the stackoverflow page * https://tex.stackexchange.com/q/745864/248249 Sincerely, Yours
Hi, LuaTeX team, I'm writing this email to append the complete steps about how I found the problem mentioned in the forwarded email. I want to take a number after a macro and use the content after number. For example, scale the baseline skip and then output the later content: \begingroup\endlinechar=-1 \newcount\scalecount \long\gdef\scaleBase{ \afterassignment\scaleBaseWithFactor \scalecount= } \long\gdef\scaleBaseWithFactor#1{{ \divide\baselineskip by 1000 \multiply\baselineskip by \scalecount #1 }} \endgroup \scaleBase1200 {line1\par line2\par line3} \bye This will show a much baseline skip between line1 and line2. I want to take \magstep values as parameter. But \scaleBase\magstep1{line1\par line2\par line3} did not work as expected. I found this is because \magstep add a \relax at the end to split itself from possible next number: $ luatex This is LuaTeX, Version 1.22.0 (TeX Live 2026/dev/Arch Linux) restricted system commands enabled. **\relax *\show\magstep
\magstep=macro: #1->\ifcase #1 \@m \or 1200\or 1440\or 1728\or 2074\or 2488\fi \relax . <*> \show\magstep
? So I add more 1 macro to strip \relax: \begingroup\endlinechar=-1 \newcount\scalecount \long\gdef\scaleBase#1{ %>>>>>>>>> \ifx#1\magstep \afterassignment\scaleBaseWithmagstep \else %<<<<<<<<< \afterassignment\scaleBaseWithFactor \fi%<<<<<<<<< \scalecount=#1 } %>>>>>>>>> \long\gdef\scaleBaseWithmagstep#1\relax#2{ \scaleBaseWithFactor{#2} } %<<<<<<<<< \long\gdef\scaleBaseWithFactor#1{{ \divide\baselineskip by 1000 \multiply\baselineskip by \scalecount #1 }} \endgroup \scaleBase\magstep1%<<<<<<<<< {line1\par line2\par line3} \bye This works fine for \magstep except \magstep0. \scaleBase\magstep0 make a warning: (\end occurred inside a group at level 1) in the log. In other more complecated cases, it report (\end occurred when \ifcase but not inside a group. So I checked the place sending \magstep. I checked this by \show#1 in \scaleBaseWithmagstep: \begingroup\endlinechar=-1 \newcount\scalecount \long\gdef\scaleBase#1{ \ifx#1\magstep \afterassignment\scaleBaseWithmagstep \else \afterassignment\scaleBaseWithFactor \fi \scalecount=#1 } \long\gdef\scaleBaseWithmagstep#1\relax#2{ \show#1%<<<<<<<<< \scaleBaseWithFactor{#2} } \long\gdef\scaleBaseWithFactor#1{{ \divide\baselineskip by 1000 \multiply\baselineskip by \scalecount #1 }} \endgroup \scaleBase\magstep1 {line1\par line2\par line3} \bye And then \scaleBase\magstep1 will \show the definition of \scaleBaseWithFactor, which may mean there is nothing before \relax, just strip \relax as expected. While \scaleBase\magstep0 report: :!f=tmp sh -c 'luatex $f.tex' This is LuaTeX, Version 1.22.0 (TeX Live 2026/dev/Arch Linux) restricted system commands enabled. (./tmp.tex
\or=\or. <argument> \or 1200\or 1440\or 1728\or 2074\or 2488\fi \scaleBaseWithmagstep #1\relax #2->\show #1 \scaleBaseWithFactor {#2} l.27 \scaleBase\magstep0{}
apply \or before 1200 to \show.
It seems that:
* For \magstep1
* \afterassignment insert \scaleBaseWithmagstep after the full \ifcase
* For \magstep0
* \afterassignment insert \scaleBaseWithmagstep before the 1st \or.
________________________________
From: li lu
Sent: Sunday, June 8, 2025 3:27 PM
To: dev-luatex@ntg.nl
On 08/06/2025 08:27, li lu wrote:
Hi LuaTeX Team, I am writing to report strange behavior of the \magstep0 command , or the original magnification \csname @m\endcsname. The problem is happened in a macro with \afterassignment and then assign \magstep0 to a count register. For the LuaTeX version: luatex --version
This is LuaTeX, Version 1.22.0 (TeX Live 2026/dev/Arch Linux) Development id: 7674 Execute 'luatex --credits' for credits and version details.
There is NO warranty. Redistribution of this software is covered by the terms of the GNU General Public License, version 2 or (at your option) any later version. For more information about these matters, see the file named COPYING and the LuaTeX source.
LuaTeX is Copyright 2025 Taco Hoekwater and the LuaTeX Team.
The problem is happened in a macro with \afterassignment and then assign \magstep0 to a count register. A shortest description: ```
\newcount\count \def\problemhere#1\relax#2{\string#1#2} \def\todo{ \afterassignment\problemhere \count= }
``` For the above macro, \todo\magstep1{HERE} just print HERE while \todo\magstep0{HERE} print \or1200HERE. It seems that \magstep0 break the \ifcase structure in the \magstep definition, It seems that this is not a expected behavior. Complete use case steps and more details are on the stackoverflow page
* https://tex.stackexchange.com/q/745864/248249
Sincerely, Yours
As I've noted on TeX-sx, this is simply standard TeX expansion - it's not LuaTeX-specific. Regards, Joseph
On 6/8/2025 9:27 AM, li lu wrote:
|\newcount\count \def\problemhere#1\relax#2{\string#1#2} \def\todo{ \afterassignment\problemhere \count= } |
when redefining \count is an option for you then \magstep is the least of your worries anyway, not a bug, just related to how tex parses integers and ifcase Hans ----------------------------------------------------------------- Hans Hagen | PRAGMA ADE Ridderstraat 27 | 8061 GH Hasselt | The Netherlands tel: 038 477 53 69 | www.pragma-ade.nl | www.pragma-pod.nl -----------------------------------------------------------------
On 08/06/2025 11:53, Hans Hagen wrote:
On 6/8/2025 9:27 AM, li lu wrote:
|\newcount\count \def\problemhere#1\relax#2{\string#1#2} \def\todo{ \afterassignment\problemhere \count= } |
when redefining \count is an option for you then \magstep is the least of your worries
:) Joseph
participants (3)
-
Hans Hagen -
Joseph Wright -
li lu