From 6d6d627ca49244d53928b6e0e1a238495cef4bd2 Mon Sep 17 00:00:00 2001
From: Erik Demaine <edemaine@mit.edu>
Date: Tue, 26 Oct 2021 19:10:20 -0400
Subject: [PATCH] perf: Avoid vertical-align:0em style (#3358)

Avoid emitting `vertical-align:0em` by protecting each such style
setting with an `if`.

Fixes #3351

Co-authored-by: ylemkimon <y@ylem.kim>
---
 src/buildHTML.js                      | 8 ++++++--
 src/environments/array.js             | 6 ++++--
 src/functions/lap.js                  | 4 +++-
 test/__snapshots__/katex-spec.js.snap | 8 ++++----
 4 files changed, 17 insertions(+), 9 deletions(-)

diff --git a/src/buildHTML.js b/src/buildHTML.js
index a13b28bb..df6d95a1 100644
--- a/src/buildHTML.js
+++ b/src/buildHTML.js
@@ -300,7 +300,9 @@ function buildHTMLUnbreakable(children, options) {
     // falls at the depth of the expression.
     const strut = makeSpan(["strut"]);
     strut.style.height = (body.height + body.depth) + "em";
-    strut.style.verticalAlign = -body.depth + "em";
+    if (body.depth) {
+        strut.style.verticalAlign = -body.depth + "em";
+    }
     body.children.unshift(strut);
 
     return body;
@@ -394,7 +396,9 @@ export default function buildHTML(tree: AnyParseNode[], options: Options): DomSp
     if (tagChild) {
         const strut = tagChild.children[0];
         strut.style.height = (htmlNode.height + htmlNode.depth) + "em";
-        strut.style.verticalAlign = (-htmlNode.depth) + "em";
+        if (htmlNode.depth) {
+            strut.style.verticalAlign = (-htmlNode.depth) + "em";
+        }
     }
 
     return htmlNode;
diff --git a/src/environments/array.js b/src/environments/array.js
index 3feb589e..d2d99be9 100644
--- a/src/environments/array.js
+++ b/src/environments/array.js
@@ -381,8 +381,10 @@ const htmlBuilder: HtmlBuilder<"array"> = function(group, options) {
                 separator.style.borderRightWidth = `${ruleThickness}em`;
                 separator.style.borderRightStyle = lineType;
                 separator.style.margin = `0 -${ruleThickness / 2}em`;
-                separator.style.verticalAlign =
-                    -(totalHeight - offset) + "em";
+                const shift = totalHeight - offset;
+                if (shift) {
+                    separator.style.verticalAlign = -shift + "em";
+                }
 
                 cols.push(separator);
             } else {
diff --git a/src/functions/lap.js b/src/functions/lap.js
index cb84c09b..5507df11 100644
--- a/src/functions/lap.js
+++ b/src/functions/lap.js
@@ -47,7 +47,9 @@ defineFunction({
         // This code resolved issue #1153
         const strut = buildCommon.makeSpan(["strut"]);
         strut.style.height = (node.height + node.depth) + "em";
-        strut.style.verticalAlign = -node.depth + "em";
+        if (node.depth) {
+            strut.style.verticalAlign = -node.depth + "em";
+        }
         node.children.unshift(strut);
 
         // Next, prevent vertical misplacement when next to something tall.
diff --git a/test/__snapshots__/katex-spec.js.snap b/test/__snapshots__/katex-spec.js.snap
index 8cd15a12..5de278b8 100755
--- a/test/__snapshots__/katex-spec.js.snap
+++ b/test/__snapshots__/katex-spec.js.snap
@@ -1089,7 +1089,7 @@ exports[`Extending katex by new fonts and symbols Add new font class to new exte
   >
     <span class="base">
       <span class="strut"
-            style="height:0.84425em;vertical-align:0em;"
+            style="height:0.84425em;"
       >
       </span>
       <span class="mord mockEasternArabicFont-Regular">
@@ -1170,7 +1170,7 @@ exports[`Newlines via \\\\ and \\newline \\\\ causes newline, even after mrel an
   >
     <span class="base">
       <span class="strut"
-            style="height:0.68333em;vertical-align:0em;"
+            style="height:0.68333em;"
       >
       </span>
       <span class="mord mathnormal"
@@ -1208,7 +1208,7 @@ exports[`Newlines via \\\\ and \\newline \\\\ causes newline, even after mrel an
     </span>
     <span class="base">
       <span class="strut"
-            style="height:0.69444em;vertical-align:0em;"
+            style="height:0.69444em;"
       >
       </span>
       <span class="mord mathnormal">
@@ -1219,7 +1219,7 @@ exports[`Newlines via \\\\ and \\newline \\\\ causes newline, even after mrel an
     </span>
     <span class="base">
       <span class="strut"
-            style="height:0.43056em;vertical-align:0em;"
+            style="height:0.43056em;"
       >
       </span>
       <span class="mord mathnormal">