Support for \' \` \^ \~ \= \u \. \" \r \H \v text-mode accents (#802)

* Support for \' \` \^ \~ \= \u \. \" \r \H \v text-mode accents

* bug fix

* Possible Safari fix

* Forbid text accents in math mode

* Switch to noncombining characters for most accents. Revert Safari change.

* Add tests

* Found non-combining diaresis accent too

src/Parser.js

@@ -561,6 +561,11 @@ class Parser {
                     throw new ParseError(
                         "Can't use function '" + func + "' in text mode",
                         baseGroup.token);
+                } else if (this.mode === "math" &&
+                    funcData.allowedInMath === false) {
+                    throw new ParseError(
+                        "Can't use function '" + func + "' in math mode",
+                        baseGroup.token);
                 }
 
                 const args = this.parseArguments(func, funcData);

src/buildHTML.js

@@ -1392,7 +1392,7 @@ groupTypes.accent = function(group, options) {
     let accentBody;
     if (!group.value.isStretchy) {
         const accent = buildCommon.makeSymbol(
-            group.value.label, "Main-Regular", "math", options);
+            group.value.label, "Main-Regular", group.mode, options);
         // Remove the italic correction of the accent, because it only serves to
         // shift the accent over to a place we don't want.
         accent.italic = 0;
@@ -1401,10 +1401,17 @@ groupTypes.accent = function(group, options) {
         // thus shows up much too far to the left. To account for this, we add a
         // specific class which shifts the accent over to where we want it.
         // TODO(emily): Fix this in a better way, like by changing the font
-        const vecClass = group.value.label === "\\vec" ? "accent-vec" : null;
+        // Similarly, text accent \H is a combining character and
+        // requires a different adjustment.
+        let accentClass = null;
+        if (group.value.label === "\\vec") {
+            accentClass = "accent-vec";
+        } else if (group.value.label === '\\H') {
+            accentClass = "accent-hungarian";
+        }
 
-        accentBody = makeSpan(["accent-body", vecClass], [
-            makeSpan([], [accent])]);
+        accentBody = makeSpan([], [accent]);
+        accentBody = makeSpan(["accent-body", accentClass], [accentBody]);
 
         // Shift the accent over by the skew. Note we shift by twice the skew
         // because we are centering the accent, so by adding 2*skew to the left,

src/functions.js

@@ -92,6 +92,7 @@ function defineFunction(names, props, handler) {
         argTypes: props.argTypes,
         greediness: (props.greediness === undefined) ? 1 : props.greediness,
         allowedInText: !!props.allowedInText,
+        allowedInMath: props.allowedInMath,
         numOptionalArgs: props.numOptionalArgs || 0,
         infix: !!props.infix,
         handler: handler,
@@ -660,6 +661,27 @@ defineFunction([
     };
 });
 
+// Text-mode accents
+defineFunction([
+    "\\'", "\\`", "\\^", "\\~", "\\=", "\\u", "\\.", '\\"',
+    "\\r", "\\H", "\\v",
+], {
+    numArgs: 1,
+    allowedInText: true,
+    allowedInMath: false,
+}, function(context, args) {
+    const base = args[0];
+
+    return {
+        type: "accent",
+        label: context.funcName,
+        isStretchy: false,
+        isShifty: true,
+        value: ordargument(base),
+        base: base,
+    };
+});
+
 // Horizontal stretchy braces
 defineFunction([
     "\\overbrace", "\\underbrace",

src/symbols.js

@@ -616,6 +616,17 @@ defineSymbol(math, main, accent, "\u20d7", "\\vec");
 defineSymbol(math, main, accent, "\u02d9", "\\dot");
 defineSymbol(math, main, mathord, "\u0131", "\\imath");
 defineSymbol(math, main, mathord, "\u0237", "\\jmath");
+defineSymbol(text, main, accent, "\u02ca", "\\'"); // acute
+defineSymbol(text, main, accent, "\u02cb", "\\`"); // grave
+defineSymbol(text, main, accent, "\u02c6", "\\^"); // circumflex
+defineSymbol(text, main, accent, "\u02dc", "\\~"); // tilde
+defineSymbol(text, main, accent, "\u02c9", "\\="); // macron
+defineSymbol(text, main, accent, "\u02d8", "\\u"); // breve
+defineSymbol(text, main, accent, "\u02d9", "\\."); // dot above
+defineSymbol(text, main, accent, "\u02da", "\\r"); // ring above
+defineSymbol(text, main, accent, "\u02c7", "\\v"); // caron
+defineSymbol(text, main, accent, "\u00a8", '\\"'); // diaresis
+defineSymbol(text, main, accent, "\u030B", "\\H"); // double acute
 
 defineSymbol(text, main, textord, "\u2013", "--");
 defineSymbol(text, main, textord, "\u2013", "\\textendash");

static/katex.less

@@ -502,6 +502,11 @@
             // it left. We center it by shifting it half way right again.
             left: 0.326em;
         }
+
+        .accent-body.accent-hungarian > span {
+            position: relative;
+            left: 0.250em; // width of space
+        }
     }
 
     .mtable {

test/errors-spec.js

@@ -140,6 +140,11 @@ describe("Parser:", function() {
                 "Can't use function '\\sqrt' in text mode" +
                 " at position 7: \\text{\\̲s̲q̲r̲t̲2 is irrational…");
         });
+        it("rejects text-mode-only functions in math mode", function() {
+            expect("\\'echec").toFailWithParseError(
+                "Can't use function '\\'' in math mode" +
+                " at position 1: \\̲'̲echec");
+        });
     });
 
     describe("#parseArguments", function() {

test/screenshotter/ss_data.yaml

@@ -12,6 +12,11 @@
 # on the next line. See http://www.yaml.org/ for syntax details.
 
 Accents: \vec{A}\vec{x}\vec x^2\vec{x}_2^2\vec{A}^2\vec{xA}^2
+AccentsText: |
+    \begin{array}{l}
+    \text{\H{e}}\\
+    \text{\H{X}}\\
+    \end{array}
 Aligned: |
     \begin{aligned}
         a &= 1 & b &= 2 \\