From cbd3afd738eff4bd803e2995e422c1134e4cef36 Mon Sep 17 00:00:00 2001
From: Erik Demaine <edemaine@mit.edu>
Date: Mon, 23 Jul 2018 13:01:02 -0400
Subject: [PATCH] Fix \not vertical alignment (#1497)

* Fix \not vertical alignment

Fix #1491 by changing from `position: absolute` to `position: relative`.

* Switch to \rlap implementation of \not

* Separate \not the macro from \not the symbol via \@not

* Fix test
---
 src/buildHTML.js   | 9 ---------
 src/macros.js      | 6 ++++++
 src/symbols.js     | 2 +-
 test/katex-spec.js | 6 +++++-
 4 files changed, 12 insertions(+), 11 deletions(-)

diff --git a/src/buildHTML.js b/src/buildHTML.js
index 330866a5..6a7e6ce0 100644
--- a/src/buildHTML.js
+++ b/src/buildHTML.js
@@ -183,15 +183,6 @@ export const buildExpression = function(
         }
     }
 
-    // Process \\not commands within the group.
-    for (let i = 0; i < groups.length; i++) {
-        const group = groups[i];
-        if (group instanceof domTree.symbolNode && group.value === "\u0338") {
-            // Results in a solidus being overlaid over the following group/atom.
-            group.style.position = "absolute";
-        }
-    }
-
     return groups;
 };
 
diff --git a/src/macros.js b/src/macros.js
index 5eb44849..7419e4f0 100644
--- a/src/macros.js
+++ b/src/macros.js
@@ -357,6 +357,12 @@ defineMacro("\\llap", "\\mathllap{\\textrm{#1}}");
 defineMacro("\\rlap", "\\mathrlap{\\textrm{#1}}");
 defineMacro("\\clap", "\\mathclap{\\textrm{#1}}");
 
+// \not is defined by base/fontmath.ltx via
+// \DeclareMathSymbol{\not}{\mathrel}{symbols}{"36}
+// It's thus treated like a \mathrel, but defined by a symbol that has zero
+// width but extends to the right.  We use \rlap to get that spacing.
+defineMacro("\\not", '\\mathrel{\\mathrlap\\@not}');
+
 // Negated symbols from base/fontmath.ltx:
 // \def\neq{\not=} \let\ne=\neq
 // \DeclareRobustCommand
diff --git a/src/symbols.js b/src/symbols.js
index d31b6e51..0cdf674c 100644
--- a/src/symbols.js
+++ b/src/symbols.js
@@ -563,7 +563,7 @@ defineSymbol(math, main, rel, "\u2265", "\\geq", true);
 defineSymbol(math, main, rel, "\u2190", "\\gets");
 defineSymbol(math, main, rel, ">", "\\gt");
 defineSymbol(math, main, rel, "\u2208", "\\in", true);
-defineSymbol(math, main, rel, "\u0338", "\\not");
+defineSymbol(math, main, rel, "\u0338", "\\@not");
 defineSymbol(math, main, rel, "\u2282", "\\subset", true);
 defineSymbol(math, main, rel, "\u2283", "\\supset", true);
 defineSymbol(math, main, rel, "\u2286", "\\subseteq", true);
diff --git a/test/katex-spec.js b/test/katex-spec.js
index 6d9ac0d1..bb0b57fe 100644
--- a/test/katex-spec.js
+++ b/test/katex-spec.js
@@ -93,7 +93,11 @@ describe("A rel parser", function() {
             if (group.type === "htmlmathml") {
                 group = group.value.html[0];
             }
-            expect(group.type).toEqual("rel");
+            if (group.type === "mclass") {
+                expect(group.value.mclass).toEqual("mrel");
+            } else {
+                expect(group.type).toEqual("rel");
+            }
         }
     });
 });