Added support for bold italic symbols (#1011)

* added support for \boldsymbol

* added \boldsymbol tests

* added \boldsymbol screenshots

* added \bm, snapshot, updated screenshots

* updated snapshot for \boldsymbol

* properly display \imath and 2 in boldsymbol

* implemented \boldsymbol for +

* fix typo, remove boldsymbolLetters hardcode

* make comment about using Main-Bold more general

* fixed trailing space CI error

src/buildCommon.js

@@ -113,8 +113,13 @@ const mathsym = function(
     // Have a special case for when the value = \ because the \ is used as a
     // textord in unsupported command errors but cannot be parsed as a regular
     // text ordinal and is therefore not present as a symbol in the symbols
-    // table for text
+    // table for text, as well as a special case for boldsymbol because it
-    if (value === "\\" || symbols[mode][value].font === "main") {
+    // can be used for bold + and -
+    if ((options && options.font && options.font === "boldsymbol") &&
+            lookupSymbol(value, "Main-Bold", mode).metrics) {
+        return makeSymbol(value, "Main-Bold", mode, options,
+            classes.concat(["mathbf"]));
+    } else if (value === "\\" || symbols[mode][value].font === "main") {
         return makeSymbol(value, "Main-Regular", mode, options, classes);
     } else {
         return makeSymbol(
@@ -179,6 +184,33 @@ const mathit = function(
     }
 };
 
+/**
+ * Determines which of the two font names (Main-Bold and Math-BoldItalic) and
+ * corresponding style tags (mathbf or boldsymbol) to use for font "boldsymbol",
+ * depending on the symbol.  Use this function instead of fontMap for font
+ * "boldsymbol".
+ */
+const boldsymbol = function(
+    value: string,
+    mode: Mode,
+    options: Options,
+    classes: string[],
+): {| fontName: string, fontClass: string |} {
+    if (lookupSymbol(value, "Math-BoldItalic", mode).metrics) {
+        return {
+            fontName: "Math-BoldItalic",
+            fontClass: "boldsymbol",
+        };
+    } else {
+        // Some glyphs do not exist in Math-BoldItalic so we need to use
+        // Main-Bold instead.
+        return {
+            fontName: "Main-Bold",
+            fontClass: "mathbf",
+        };
+    }
+};
+
 /**
  * Makes either a mathord or textord in the correct font and color.
  */
@@ -195,7 +227,9 @@ const makeOrd = function(
     const font = options.font;
     if (font) {
         let fontLookup;
-        if (font === "mathit" || utils.contains(mainitLetters, value)) {
+        if (font === "boldsymbol") {
+            fontLookup = boldsymbol(value, mode, options, classes);
+        } else if (font === "mathit" || utils.contains(mainitLetters, value)) {
             fontLookup = mathit(value, mode, options, classes);
         } else {
             fontLookup = fontMap[font];
@@ -590,9 +624,10 @@ const fontMap: {[string]: {| variant: string, fontName: string |}} = {
         fontName: "Main-Italic",
     },
 
-    // "mathit" is missing because it requires the use of two fonts: Main-Italic
+    // "mathit" and "boldsymbol" are missing because they require the use of two
-    // and Math-Italic.  This is handled by a special case in makeOrd which ends
+    // fonts: Main-Italic and Math-Italic for "mathit", and Math-BoldItalic and
-    // up calling mathit.
+    // Main-Bold for "boldsymbol".  This is handled by a special case in makeOrd
+    // which ends up calling mathit and boldsymbol.
 
     // families
     "mathbb": {

src/buildMathML.js

@@ -39,6 +39,8 @@ const getVariant = function(group, options) {
     const mode = group.mode;
     if (font === "mathit") {
         return "italic";
+    } else if (font === "boldsymbol") {
+        return "bold-italic";
     }
 
     let value = group.value;
@@ -106,10 +108,15 @@ groupTypes.textord = function(group, options) {
     return node;
 };
 
-groupTypes.bin = function(group) {
+groupTypes.bin = function(group, options) {
     const node = new mathMLTree.MathNode(
         "mo", [makeText(group.value, group.mode)]);
 
+    const variant = getVariant(group, options);
+    if (variant === "bold-italic") {
+        node.setAttribute("mathvariant", variant);
+    }
+
     return node;
 };
 

src/functions.js

@@ -147,6 +147,7 @@ const fontAliases = {
     "\\Bbb": "\\mathbb",
     "\\bold": "\\mathbf",
     "\\frak": "\\mathfrak",
+    "\\bm": "\\boldsymbol",
 };
 
 const singleCharIntegrals: {[string]: string} = {
@@ -244,14 +245,14 @@ defineFunction([
 
 defineFunction([
     // styles
-    "\\mathrm", "\\mathit", "\\mathbf",
+    "\\mathrm", "\\mathit", "\\mathbf", "\\boldsymbol",
 
     // families
     "\\mathbb", "\\mathcal", "\\mathfrak", "\\mathscr", "\\mathsf",
     "\\mathtt",
 
     // aliases
-    "\\Bbb", "\\bold", "\\frak",
+    "\\Bbb", "\\bold", "\\frak", "\\bm",
 ], {
     numArgs: 1,
     greediness: 2,

static/katex.less

@@ -75,6 +75,12 @@
         font-weight: bold;
     }
 
+    .boldsymbol {
+        font-family: KaTeX_Math;
+        font-weight: bold;
+        font-style: italic;
+    }
+
     .amsrm {
         font-family: KaTeX_AMS;
     }

test/__snapshots__/mathml-spec.js.snap

@@ -77,6 +77,46 @@ exports[`A MathML builder should make prime operators into <mo> nodes 1`] = `
 
 `;
 
+exports[`A MathML builder should render boldsymbol with the correct mathvariants 1`] = `
+
+<math>
+  <semantics>
+    <mrow>
+      <mrow>
+        <mi mathvariant="bold-italic">
+          A
+        </mi>
+        <mi mathvariant="bold-italic">
+          x
+        </mi>
+        <mn mathvariant="bold-italic">
+          2
+        </mn>
+        <mi mathvariant="bold-italic">
+          k
+        </mi>
+        <mi mathvariant="bold-italic">
+          ω
+        </mi>
+        <mi mathvariant="bold-italic">
+          Ω
+        </mi>
+        <mi mathvariant="bold-italic">
+          ı
+        </mi>
+        <mo mathvariant="bold-italic">
+          +
+        </mo>
+      </mrow>
+    </mrow>
+    <annotation encoding="application/x-tex">
+      \\boldsymbol{Ax2k\\omega\\Omega\\imath+}
+    </annotation>
+  </semantics>
+</math>
+
+`;
+
 exports[`A MathML builder should render mathchoice as if there was nothing 1`] = `
 
 <math>

test/mathml-spec.js

@@ -75,4 +75,9 @@ describe("A MathML builder", function() {
         expect(getMathML(`x_{y_{\\mathchoice{D}{T}{S}{${cmd}}}}`))
             .toMatchSnapshot();
     });
+
+    it("should render boldsymbol with the correct mathvariants", () => {
+        expect(getMathML(`\\boldsymbol{Ax2k\\omega\\Omega\\imath+}`))
+            .toMatchSnapshot();
+    });
 });

test/screenshotter/ss_data.yaml

@@ -57,6 +57,7 @@ BinCancellation: |
     \end{array}
 BinomTest: \dbinom{a}{b}\tbinom{a}{b}^{\binom{a}{b}+17}
 BoldSpacing: \mathbf{A}^2+\mathbf{B}_3*\mathscr{C}'
+BoldSymbol: \sum_{\boldsymbol{\alpha}}^{\boldsymbol{\beta}} \boldsymbol{\omega}+ \int_{\boldsymbol{\alpha}}^{\boldsymbol{\beta}} \boldsymbol{\Omega}+\boldsymbol{Ax2k\omega\Omega\imath+}
 Boxed: \boxed{F=ma} \quad \boxed{ac}\color{magenta}{\boxed{F}}\boxed{F=mg}
 Cases: |
     f(a,b)=\begin{cases}