[latex3-commits] [latex3/luaotfload] dev: Add comment regarding rot13 (be130bb5)

[github at latex-project.org]

Repository : https://github.com/latex3/luaotfload
On branch  : dev
Link       : https://github.com/latex3/luaotfload/commit/be130bb503439b94144259525e58178b4d4a1086

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

commit be130bb503439b94144259525e58178b4d4a1086
Author: Marcel Fabian Krüger <tex at 2krueger.de>
Date:   Fri Jul 21 20:37:56 2023 +0200

    Add comment regarding rot13


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be130bb503439b94144259525e58178b4d4a1086
 src/luaotfload-features.lua | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/src/luaotfload-features.lua b/src/luaotfload-features.lua
index fbf3ef80..d65e7f93 100644
--- a/src/luaotfload-features.lua
+++ b/src/luaotfload-features.lua
@@ -614,6 +614,13 @@ local tlig_specification = {
     },
 }
 
+-- "substitution" features allow to replace individual characters with other
+-- characters. This is often used inside of fonts to e.g. implement stylistic
+-- sets.
+-- As an example how such features can be added in the fontloader, we have a
+-- simple implementation of the ROT13 cipher as a font feature. It can be
+-- used by enabling the `rot13` font feature in a font, but we are not aware of
+-- any practical usecase for this.
 local rot13_specification = {
     type      = "substitution",
     features  = everywhere,