[latex3-commits] [git/LaTeX3-latex3-latex2e] gh1033: Extend docs (58390c1a)

[Joseph Wright]

Repository : https://github.com/latex3/latex2e
On branch  : gh1033
Link       : https://github.com/latex3/latex2e/commit/58390c1a2e1167f499b66fc216429649aff1c38a

>---------------------------------------------------------------

commit 58390c1a2e1167f499b66fc216429649aff1c38a
Author: Joseph Wright <joseph.wright at morningstar2.co.uk>
Date:   Thu Apr 20 09:18:13 2023 +0100

    Extend docs
    
    I don't currently have a good example for
    locale-specific tuning!


>---------------------------------------------------------------

58390c1a2e1167f499b66fc216429649aff1c38a
 base/doc/ltnews37.tex |  9 ++++++++-
 base/doc/usrguide.tex | 12 +++++++++---
 2 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/base/doc/ltnews37.tex b/base/doc/ltnews37.tex
index 718d195d..fc28934c 100644
--- a/base/doc/ltnews37.tex
+++ b/base/doc/ltnews37.tex
@@ -356,7 +356,14 @@ been addressed by the addition of three commands
 which can be used to customise the outcome for codepoints. This can be apply
 generally or to a specific locale (see also the next section). A small number
 of pre-defined customisations have been set up in the kernel where the outcomes
-for \pdfTeX{} should be different for those from Unicode engines.
+for \pdfTeX{} should be different for those from Unicode engines. For
+example
+\begin{quotation}
+  |\DeclareUppercaseMapping{"01F0}{\v{J}|
+\end{quotation}
+allows \v{J} to be produced in 8-bit engines: without this customisation,
+an error would occur as there is no pre-composed \v{J} in Unicode. More detail
+is given in \texttt{usrguide}.
 %
 \githubissue{1033}
 
diff --git a/base/doc/usrguide.tex b/base/doc/usrguide.tex
index b7d550ca..c7e900c4 100644
--- a/base/doc/usrguide.tex
+++ b/base/doc/usrguide.tex
@@ -1229,8 +1229,14 @@ codepoints
 All three take a \meta{codepoint} (as an integer expression) and will
 result in the \meta{output} being produced under the appropriate case changing
 operation. The optional \meta{locale} can be given if the mapping should only
-apply to a specific one: this is given in BCP-47 format.
-
-All three take the same arguments
+apply to a specific one: this is given in BCP-47 format
+(\url{https://en.wikipedia.org/wiki/IETF_language_tag}). For example,
+the kernel customises the mapping for U+01F0 (\v{j}) when uppercasing in
+8-bit engines:
+\begin{quotation}
+  |\DeclareUppercaseMapping{"01F0}{\v{J}|
+\end{quotation}
+as there is no pre-composed \v{J} character, and this is problematic if
+the engine does not support Unicode natively.
 
 \end{document}