fix(math): Add missing MathML mathvariant mappings

Author: Omikhleia

packages/math/base-elements.lua

@@ -2,6 +2,8 @@ local nodefactory = require("types.node")
 local hb = require("justenoughharfbuzz")
 local ot = require("core.opentype-parser")
 local syms = require("packages.math.unicode-symbols")
+local mathvariants = require("packages.math.unicode-mathvariants")
+local convertMathVariantScript = mathvariants.convertMathVariantScript
 
 local atomType = syms.atomType
 local symbolDefaults = syms.symbolDefaults
@@ -19,32 +21,6 @@ local mathMode = {
    scriptScriptCramped = 7,
 }
 
-local scriptType = {
-   upright = 1,
-   bold = 2, -- also have Greek and digits
-   italic = 3, -- also have Greek
-   boldItalic = 4, -- also have Greek
-   script = 5,
-   boldScript = 6,
-   fraktur = 7,
-   boldFraktur = 8,
-   doubleStruck = 9, -- also have digits
-   sansSerif = 10, -- also have digits
-   sansSerifBold = 11, -- also have Greek and digits
-   sansSerifItalic = 12,
-   sansSerifBoldItalic = 13, -- also have Greek
-   monospace = 14, -- also have digits
-}
-
-local mathVariantToScriptType = function (attr)
-   return attr == "normal" and scriptType.upright
-      or attr == "bold" and scriptType.bold
-      or attr == "italic" and scriptType.italic
-      or attr == "bold-italic" and scriptType.boldItalic
-      or attr == "double-struck" and scriptType.doubleStruck
-      or SU.error('Invalid value "' .. attr .. '" for option mathvariant')
-end
-
 local function isDisplayMode (mode)
    return mode <= 1
 end
@@ -61,50 +37,6 @@ local function isScriptScriptMode (mode)
    return mode == mathMode.scriptScript or mode == mathMode.scriptScriptCramped
 end
 
-local mathScriptConversionTable = {
-   capital = {
-      [scriptType.upright] = function (codepoint)
-         return codepoint
-      end,
-      [scriptType.bold] = function (codepoint)
-         return codepoint + 0x1D400 - 0x41
-      end,
-      [scriptType.italic] = function (codepoint)
-         return codepoint + 0x1D434 - 0x41
-      end,
-      [scriptType.boldItalic] = function (codepoint)
-         return codepoint + 0x1D468 - 0x41
-      end,
-      [scriptType.doubleStruck] = function (codepoint)
-         return codepoint == 0x43 and 0x2102
-            or codepoint == 0x48 and 0x210D
-            or codepoint == 0x4E and 0x2115
-            or codepoint == 0x50 and 0x2119
-            or codepoint == 0x51 and 0x211A
-            or codepoint == 0x52 and 0x211D
-            or codepoint == 0x5A and 0x2124
-            or codepoint + 0x1D538 - 0x41
-      end,
-   },
-   small = {
-      [scriptType.upright] = function (codepoint)
-         return codepoint
-      end,
-      [scriptType.bold] = function (codepoint)
-         return codepoint + 0x1D41A - 0x61
-      end,
-      [scriptType.italic] = function (codepoint)
-         return codepoint == 0x68 and 0x210E or codepoint + 0x1D44E - 0x61
-      end,
-      [scriptType.boldItalic] = function (codepoint)
-         return codepoint + 0x1D482 - 0x61
-      end,
-      [scriptType.doubleStruck] = function (codepoint)
-         return codepoint + 0x1D552 - 0x61
-      end,
-   },
-}
-
 local mathCache = {}
 
 local function retrieveMathTable (font)
@@ -952,16 +884,7 @@ function elements.text:_init (kind, attributes, script, text)
    self.script = script
    self.text = text
    if self.script ~= "upright" then
-      local converted = ""
-      for _, uchr in luautf8.codes(self.text) do
-         local dst_char = luautf8.char(uchr)
-         if uchr >= 0x41 and uchr <= 0x5A then -- Latin capital letter
-            dst_char = luautf8.char(mathScriptConversionTable.capital[self.script](uchr))
-         elseif uchr >= 0x61 and uchr <= 0x7A then -- Latin non-capital letter
-            dst_char = luautf8.char(mathScriptConversionTable.small[self.script](uchr))
-         end
-         converted = converted .. dst_char
-      end
+      local converted = convertMathVariantScript(self.text, self.script)
       self.originalText = self.text
       self.text = converted
    end
@@ -1521,8 +1444,6 @@ end
 
 elements.mathMode = mathMode
 elements.atomType = atomType
-elements.scriptType = scriptType
-elements.mathVariantToScriptType = mathVariantToScriptType
 elements.symbolDefaults = symbolDefaults
 elements.newSubscript = newSubscript
 elements.newUnderOver = newUnderOver

packages/math/texlike.lua

@@ -444,7 +444,7 @@ local function printMathML (tree)
    if tree.options then
       local options = {}
       for k, v in pairs(tree.options) do
-         table.insert(options, k .. "=" .. v)
+         table.insert(options, k .. "=" .. tostring(v))
       end
       if #options > 0 then
          result = result .. "[" .. table.concat(options, ", ") .. "]"
@@ -530,6 +530,21 @@ compileToMathML(
   \def{quad}{\mspace[width=1em]}
   \def{qquad}{\mspace[width=2em]}
 
+  % MathML says a single-character identifier must be in italic by default.
+  % TeX however has the following Greek capital macros rendered in upright shape.
+  % It so common that you've probably never seen Γ(x) written with an italic gamma.
+  \def{Gamma}{\mi[mathvariant=normal]{Γ}}
+  \def{Delta}{\mi[mathvariant=normal]{Δ}}
+  \def{Theta}{\mi[mathvariant=normal]{Θ}}
+  \def{Lambda}{\mi[mathvariant=normal]{Λ}}
+  \def{Xi}{\mi[mathvariant=normal]{Ξ}}
+  \def{Pi}{\mi[mathvariant=normal]{Π}}
+  \def{Sigma}{\mi[mathvariant=normal]{Σ}}
+  \def{Upsilon}{\mi[mathvariant=normal]{Υ}}
+  \def{Phi}{\mi[mathvariant=normal]{Φ}}
+  \def{Psi}{\mi[mathvariant=normal]{Ψ}}
+  \def{Omega}{\mi[mathvariant=normal]{Ω}}
+
   % Modulus operator forms
   \def{bmod}{\mo{mod}}
   \def{pmod}{\quad(\mo{mod} #1)}

packages/math/typesetter.lua

@@ -1,6 +1,8 @@
 -- Interpret a MathML or TeX-like AST, typeset it and add it to the output.
 local b = require("packages.math.base-elements")
 local syms = require("packages.math.unicode-symbols")
+local mathvariants = require("packages.math.unicode-mathvariants")
+local mathVariantToScriptType, scriptType = mathvariants.mathVariantToScriptType, mathvariants.scriptType
 
 -- Shorthands for atom types, used in the `atom` command option
 local atomTypeShort = {
@@ -47,16 +49,16 @@ function ConvertMathML (_, content)
       local special = content.options.special
       return b.phantom(convertChildren(content), special)
    elseif content.command == "mi" then
-      local script = content.options.mathvariant and b.mathVariantToScriptType(content.options.mathvariant)
+      local script = content.options.mathvariant and mathVariantToScriptType(content.options.mathvariant)
       local text = content[1]
       if type(text) ~= "string" then
          SU.error("mi command contains content which is not text")
       end
-      script = script or (luautf8.len(text) == 1 and b.scriptType.italic or b.scriptType.upright)
+      script = script or (luautf8.len(text) == 1 and scriptType.italic or scriptType.upright)
       return b.text("identifier", {}, script, text)
    elseif content.command == "mo" then
-      local script = content.options.mathvariant and b.mathVariantToScriptType(content.options.mathvariant)
-         or b.scriptType.upright
+      local script = content.options.mathvariant and mathVariantToScriptType(content.options.mathvariant)
+         or scriptType.upright
       local text = content[1]
       local attributes = {}
       if syms.symbolDefaults[text] then
@@ -76,8 +78,8 @@ function ConvertMathML (_, content)
       end
       return b.text("operator", attributes, script, text)
    elseif content.command == "mn" then
-      local script = content.options.mathvariant and b.mathVariantToScriptType(content.options.mathvariant)
-         or b.scriptType.upright
+      local script = content.options.mathvariant and mathVariantToScriptType(content.options.mathvariant)
+         or scriptType.upright
       local text = content[1]
       if type(text) ~= "string" then
          SU.error("mn command contains content which is not text")
@@ -156,7 +158,7 @@ function ConvertMathML (_, content)
       -- and soft wrap opportunities: ignored here.
       -- There's also some explanations about CSS, italic correction etc. which we ignore too.
       text = text:gsub("[\n\r]", " ")
-      return b.text("string", {}, b.scriptType.upright, text:gsub("%s+", " "))
+      return b.text("string", {}, scriptType.upright, text:gsub("%s+", " "))
    else
       SU.error("Unknown math command " .. content.command)
    end