From deb5a01766c2d947ed5fbc0797f3030b64491ab5 Mon Sep 17 00:00:00 2001
From: Omikhleia <didier.willis@gmail.com>
Date: Tue, 19 Nov 2024 23:49:25 +0100
Subject: [PATCH] fix(math): Add math.font.features setting, defaulting to
 +ssty for Libertinus Math

---
 packages/math/base-elements.lua | 1 +
 packages/math/init.lua          | 7 +++++++
 2 files changed, 8 insertions(+)

diff --git a/packages/math/base-elements.lua b/packages/math/base-elements.lua
index 174f3e564..870c8894a 100644
--- a/packages/math/base-elements.lua
+++ b/packages/math/base-elements.lua
@@ -217,6 +217,7 @@ function elements.mbox:_init ()
       size = SILE.settings:get("math.font.size"),
       style = SILE.settings:get("math.font.style"),
       weight = SILE.settings:get("math.font.weight"),
+      features = SILE.settings:get("math.font.features"),
    }
    local filename = SILE.settings:get("math.font.filename")
    if filename and filename ~= "" then
diff --git a/packages/math/init.lua b/packages/math/init.lua
index 79edba25e..62aca3620 100644
--- a/packages/math/init.lua
+++ b/packages/math/init.lua
@@ -35,6 +35,11 @@ function package.declareSettings (_)
       type = "integer",
       default = 400,
    })
+   SILE.settings:declare({
+      parameter = "math.font.features",
+      type = "string or nil",
+      default = "+ssty",
+   })
    SILE.settings:declare({
       parameter = "math.font.filename",
       type = "string",
@@ -138,6 +143,8 @@ By default, this package uses Libertinus Math, so it will fail if Libertinus Mat
 Another font may be specified via the setting \autodoc:setting{math.font.family}.
 If required, you can set the font style and weight via \autodoc:setting{math.font.style} and \autodoc:setting{math.font.weight}.
 The font size can be set via \autodoc:setting{math.font.size}.
+The \autodoc:setting{math.font.features} setting can be used to specify OpenType features for the math font. It defaults to \code{+ssty} (script style), notably to ensure that some symbols such as the prime, double prime, etc. are displayed correctly.
+The default setting applies to Libertinus Math, but other fonts may require different features (e.g. the STIX Two Math font requires \code{+ss04}).
 
 \paragraph{MathML}
 The first way to typeset math formulas is to enter them in the MathML format.