Make accents zero width (#1033)

* Make accents zero width

Make the width of an accented character equal to the width of the character,
by making accents zero width.  In particular, fixes #1028 (`\ddot\imath`).

This involved reworking all of the accent offset machinery, in particular
skew and accent-hungarian.  A bit cleaner now.

Also added support for the new width character metrics in symbolNode.

* Update AccentsText test

* Fix comment

src/buildCommon.js

@@ -73,13 +73,13 @@ const makeSymbol = function(
         }
         symbolNode = new domTree.symbolNode(
             value, metrics.height, metrics.depth, italic, metrics.skew,
-            classes);
+            metrics.width, classes);
     } else {
         // TODO(emily): Figure out a good way to only print this in development
         typeof console !== "undefined" && console.warn(
             "No character metrics for '" + value + "' in style '" +
                 fontFamily + "'");
-        symbolNode = new domTree.symbolNode(value, 0, 0, 0, 0, classes);
+        symbolNode = new domTree.symbolNode(value, 0, 0, 0, 0, 0, classes);
     }
 
     if (options) {
@@ -733,6 +733,8 @@ const staticSvg = function(value: string, options: Options): domTree.span {
     const svgNode = new domTree.svgNode([path], {
         "width": width + "em",
         "height": height + "em",
+        // Override CSS rule `.katex svg { width: 100% }`
+        "style": "width:" + width + "em",
         "viewBox": "0 0 " + 1000 * width + " " + 1000 * height,
         "preserveAspectRatio": "xMinYMin",
     });

src/buildHTML.js

@@ -688,6 +688,7 @@ groupTypes.accent = function(group, options) {
             // So now we use an SVG.
             // If Safari reforms, we should consider reverting to the glyph.
             accent = buildCommon.staticSvg("vec", options);
+            accent.width = parseFloat(accent.style.width);
         } else {
             accent = buildCommon.makeSymbol(
                 group.value.label, "Main-Regular", group.mode, options);
@@ -696,22 +697,26 @@ groupTypes.accent = function(group, options) {
         // shift the accent over to a place we don't want.
         accent.italic = 0;
 
+        accentBody = makeSpan(["accent-body"], [accent]);
+
+        // CSS defines `.katex .accent .accent-body { 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 = -accent.width / 2;
+
+        // Shift the accent over by the skew.
+        left += skew;
+
         // The \H character that the fonts use is a combining character, and
-        // 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.
+        // thus shows up much too far to the left. To account for this, we add
+        // a manual shift of the width of one space.
         // TODO(emily): Fix this in a better way, like by changing the font
-        let accentClass = null;
         if (group.value.label === '\\H') {
-            accentClass = "accent-hungarian";
+            left += 0.5;  // twice width of space, or width of 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,
-        // we shift it to the right by 1*skew.
-        accentBody.style.marginLeft = 2 * skew + "em";
+        accentBody.style.left = left + "em";
 
         accentBody = buildCommon.makeVList({
             positionType: "firstBaseline",

src/domTree.js

@@ -383,6 +383,7 @@ class symbolNode implements CombinableDomNode {
     depth: number;
     italic: number;
     skew: number;
+    width: number;
     maxFontSize: number;
     classes: string[];
     style: {[string]: string};
@@ -393,6 +394,7 @@ class symbolNode implements CombinableDomNode {
         depth?: number,
         italic?: number,
         skew?: number,
+        width?: number,
         classes?: string[],
         style?: {[string]: string},
     ) {
@@ -401,6 +403,7 @@ class symbolNode implements CombinableDomNode {
         this.depth = depth || 0;
         this.italic = italic || 0;
         this.skew = skew || 0;
+        this.width = width || 0;
         this.classes = classes || [];
         this.style = style || {};
         this.maxFontSize = 0;

static/katex.less

@@ -554,13 +554,9 @@
             text-align: center;
         }
 
-        .accent-body > span {
+        .accent-body {
             width: 0;
-        }
-
-        .accent-body.accent-hungarian > span {
-            position: relative;
-            left: 0.250em; // width of space
+            position: relative; // so that 'left' can shift the accent
         }
     }
 

test/screenshotter/ss_data.yaml

@@ -14,8 +14,8 @@
 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}}\\
+    \text{\H{e}} & \text{\'\i} \\
+    \text{\H{X}} & \text{\"\i} \\
     \end{array}
 Aligned: |
     \begin{aligned}