From b74b2374e23c9c46a2a65c2f441afca22b15cf25 Mon Sep 17 00:00:00 2001
From: Erik Demaine <edemaine@mit.edu>
Date: Mon, 7 May 2018 20:44:40 -0400
Subject: [PATCH] \copyright, \textregistered, \textcircled support (#1073)

* \copyright support

* Implement \textcircled, \copyright, \textregistered
---
 src/functions/accent.js | 31 ++++++++++++++++++++++++-------
 src/katex.less          |  7 ++++++-
 src/macros.js           | 10 ++++++++++
 src/symbols.js          |  1 +
 4 files changed, 41 insertions(+), 8 deletions(-)

diff --git a/src/functions/accent.js b/src/functions/accent.js
index 0388dea6..f5b4ca30 100644
--- a/src/functions/accent.js
+++ b/src/functions/accent.js
@@ -63,7 +63,7 @@ const htmlBuilder = (group, options) => {
     }
 
     // calculate the amount of space between the body and the accent
-    const clearance = Math.min(
+    let clearance = Math.min(
         body.height,
         options.fontMetrics().xHeight);
 
@@ -91,17 +91,34 @@ const htmlBuilder = (group, options) => {
 
         accentBody = buildCommon.makeSpan(["accent-body"], [accent]);
 
-        // CSS defines `.katex .accent .accent-body { width: 0 }`
+        // "Full" accents expand the width of the resulting symbol to be
+        // at least the width of the accent, and overlap directly onto the
+        // character without any vertical offset.
+        const accentFull = (group.value.label === "\\textcircled");
+        if (accentFull) {
+            accentBody.classes.push('accent-full');
+            clearance = body.height;
+        }
+
+        // Shift the accent over by the skew.
+        let left = skew;
+
+        // CSS defines `.katex .accent .accent-body:not(.accent-full) { width: 0 }`
         // so that the accent doesn't contribute to the bounding box.
         // We need to shift the character by its width (effectively half
         // its width) to compensate.
-        let left = -width / 2;
-
-        // Shift the accent over by the skew.
-        left += skew;
+        if (!accentFull) {
+            left -= width / 2;
+        }
 
         accentBody.style.left = left + "em";
 
+        // \textcircled uses the \bigcirc glyph, so it needs some
+        // vertical adjustment to match LaTeX.
+        if (group.value.label === "\\textcircled") {
+            accentBody.style.top = ".2em";
+        }
+
         accentBody = buildCommon.makeVList({
             positionType: "firstBaseline",
             children: [
@@ -215,7 +232,7 @@ defineFunction({
     type: "accent",
     names: [
         "\\'", "\\`", "\\^", "\\~", "\\=", "\\u", "\\.", '\\"',
-        "\\r", "\\H", "\\v",
+        "\\r", "\\H", "\\v", "\\textcircled",
     ],
     props: {
         numArgs: 1,
diff --git a/src/katex.less b/src/katex.less
index 07a066a9..6f55a213 100644
--- a/src/katex.less
+++ b/src/katex.less
@@ -401,8 +401,13 @@
             text-align: center;
         }
 
-        .accent-body {
+        // Accents that are not of the accent-full class have zero width
+        // (do not contribute to the width of the final symbol).
+        .accent-body:not(.accent-full) {
             width: 0;
+        }
+
+        .accent-body {
             position: relative; // so that 'left' can shift the accent
         }
     }
diff --git a/src/macros.js b/src/macros.js
index 85f53284..8dbf8f62 100644
--- a/src/macros.js
+++ b/src/macros.js
@@ -117,6 +117,16 @@ defineMacro("\\rbrack", "]");
 defineMacro("\\aa", "\\r a");
 defineMacro("\\AA", "\\r A");
 
+// \DeclareTextCommandDefault{\textcopyright}{\textcircled{c}}
+// \DeclareTextCommandDefault{\textregistered}{\textcircled{%
+//      \check@mathfonts\fontsize\sf@size\z@\math@fontsfalse\selectfont R}}
+// \DeclareRobustCommand{\copyright}{%
+//    \ifmmode{\nfss@text{\textcopyright}}\else\textcopyright\fi}
+defineMacro("\\textcopyright", "\\textcircled{c}");
+defineMacro("\\copyright",
+    "\\TextOrMath{\\textcopyright}{\\text{\\textcopyright}}");
+defineMacro("\\textregistered", "\\textcircled{\\scriptsize R}");
+
 // Unicode double-struck letters
 defineMacro("\u2102", "\\mathbb{C}");
 defineMacro("\u210D", "\\mathbb{H}");
diff --git a/src/symbols.js b/src/symbols.js
index 58160414..87fc91e2 100644
--- a/src/symbols.js
+++ b/src/symbols.js
@@ -697,6 +697,7 @@ 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, "\u02dd", "\\H"); // double acute
+defineSymbol(text, main, accent, "\u25ef", "\\textcircled"); // \bigcirc glyph
 
 defineSymbol(text, main, textord, "\u2013", "--");
 defineSymbol(text, main, textord, "\u2013", "\\textendash");