Customizing a Mathfield

The appearance and behavior of the mathfield is highly customizable.

Here are a few common examples.

Styling

To style the mathfield define a CSS rule targeting the mathfield or use the style attribute of the <math-field> element.

This can be used to modify the appearance of the mathfield in many ways, for example changing the base font size or adding a border around it.

To display the mathfield as a block element, rather than an inline element, add an attribute style="display: block"

<p>Answer: 
  <math-field style="font-size:2rem">42</math-field>.
</p>
<p>Answer: 
  <math-field style="font-size:2rem; display: block">3.1415</math-field>
</p>

CSS Variables

To customize the appearance of the mathfield, use the following CSS variables (custom properties) in a ruleset that applies to the mathfield element.

math-field {
 --smart-fence-color: red ;
}

Set these CSS variables on any selector that applies to the <math-field> element you want to customize, for example, body. Although CSS styles are “invisible” to custom components, CSS variables are “passed through” and will affect the content of the <math-field> custom component.

Alternatively you can set these CSS variables programatically:

document.body.style.setProperty("--smart-fence-color", "red");

<style>
math-field {
  --caret-color: red;
  --selection-background-color: lightgoldenrodyellow;
  --selection-color: darkblue;
}
</style>
<math-field>
    x=\frac{-b\pm \sqrt{b^2-4ac}}{2a}
</math-field>

You can customize the appearance and zindex of the virtual keyboard panel with some CSS variables associated with a selector that applies to the virtual keyboard panel container.

Read more about customizing the virtual keyboard appearance

MathLive Parts

Because the mathfield is a custom element with a shadow DOM, its content is not directly accessible to CSS rules outside of the shadow DOM.

However, there are a few parts that can be used to style the content of the mathfield using the ::part() pseudo-element.

For example:

/* Right align the formula */
math-field::part(content) {
  text-align: right;
}

/* Right align the virtual keyboard toggle */
math-field::part(container) {
  flex-flow: row-reverse;
}

/* Hide the virtual keyboard toggle */
math-field::part(virtual-keyboard-toggle) {
  display: none;
}

/* Hide the menu toggle */
math-field::part(menu-toggle) {
  display: none;
}

Note When the menu toggle is hidden, the menu can still be opened by right-clicking on the mathfield. You can customize the menu to change this behavior.

Display Options

The appearance of a formula, in an editable mathfield or as a static representation, can be controlled with some of the following options:

Color

To change the foreground (“ink”) and background (“paper”) colors of a formula programmatically, use the mf.applyStyle() function.

To change the foreground color, use the \textcolor{}{} command. To change the background color, use the \colorbox{}{} command.

The first argument of these commands is a color specified as:

• a RGB color using the standard CSS format (#d7170b)
• a CSS color name (goldenrod)
• one of the 68 colors from dvips color name (cadetblue)
• one of the 10 Mathematica color from ColorData[97, "ColorList"] (m0 to m9)
• a color defined using the syntax from the xcolor package, for example: blue!20!black!30!green

The following color names are recommended. They can be applied using the color keys in the virtual keyboard:

These colors have been carefully selected for a balanced representation of the range of hues on the color circle, with similar lightness and intensity. They will map to different color values than the dvips colors of the same name.

To have proper legibility based on usage, these color names will map to different values when used as a foreground color and a background color. To use a specific color value, use a RGB color instead.

To customize how the color names are interpreted provide a colorMap or backgroundColorMap function.

Size

To change the base font size, set the font-size CSS property to the desired value on the mathfield or static element.

Within a formula, the size can be specified from a font scale with 10 values, where 1 em is the base font size of the mathfield or static element.

In TeX, the sizing commands behave inconsistently when applied to math. Other implementations of TeX may also interpret the sizing commands differently.

Math Layout

To control some aspects of the math typesetting, change the mathstyle with the commands \displaystyle, \textstyle, \scriptstyle, \scriptscriptstyle.

The displaystyle style is most appropriate when there is plenty of space around the formula. Limits over large operators, such as \sum are displayed above and below the operator. There is a generous amount of space below the numerator and above the denominator of fractions, and around relational (=) and binary (+) operators.

The textstyle style is useful when space is constrained or when displaying a formula with some regular text around it. The limits of large operators are displayed after the operator. The numerator and denominator of fractions is displayed using a smaller font size. However, the font-size for other characters is not affected.

The scriptstyle and scriptscriptstyle are rarely needed explicitly. The content is laid out using a smaller font-size (70% and 50% of the base font-size, respectively) and the spacing between operators is minimized. Note however that these styles are used automatically in some situations. For example, when using the displaystyle or textstyle, the limits of a large operator or the superscript or subscript of a symbol are displayed using these styles. Notice for example that n=0 in displaystyle does not include space around the = sign because the limit is displayed in scriptstyle.

To set the default mathstyle of a mathfield, set the mf.defaultMode property or the default-mode attribute.

Set it to "inline-math" to use textstyle or "math" to use displaystyle.

<p>The answer is 
  <math-field default-mode="inline-math">
    x=\frac{-b\pm \sqrt{b^2-4ac}}{2a}
  </math-field>.
</p>

By default, the mathfield element is laid out on the page as an inline element when in an inline context (when inside a <p> tag for example).

To get it laid out as a block element, set display: block on the mathfield.

Letter Shape Style

To control which letters are automatically italicized, set the letterShapeStyle property or letter-shape-style attribute.

In the ISO style, lower and uppercase roman letter and lower and upper case greek letters are italicized when used as a variable. Mathematical constants such as \(e\) are written upright.

TeX has traditionally implemented a layout option that italicizes romman letters and lowercase greek letters, but not uppercase greek letters.

The French typographical convention is to only italicize lowercase roman letters.

The default letter shape style is auto: if the system locale is “french”, the french style is used, otherwise tex is used.

Focus Ring

To change the appearance of the focus ring, use the :focus-within pseudo-element.

<style>
  math-field:focus-within {
    outline: 4px solid #d7170b;
    border-radius: 4px;
    background: rgba(251,	187,	182, .1);
  }
</style>
<math-field>
    x=\frac{-b\pm \sqrt{b^2-4ac}}{2a}
</math-field>

Caution Removing outlines in CSS creates issues for people navigating the web with a keyboard. However, you can change the appearance of the outline, for example to indicate an error condition. If you remove the outline on the mathfield, make sure to replace it with another indicator, for example by displaying an outline on an enclosing element.

<math-field smart-mode>
    x=\frac{-b\pm \sqrt{b^2-4ac}}{2a}
</math-field>

mf.mathModeSpace = '\\:';

Turning off the LaTeX mode

Pressing the \ (backslash) or ESC key switches to the LaTeX mode where it is possible to enter raw LaTeX command. For users familiar with LaTeX, it is a powerful way to enter or edit LaTeX in an expression. However, users unfamiliar with LaTeX may be confused if they accidentally press those keys.

To prevent the LaTeX mode from being enabled intercept the trigger keys and call `preventDefault().

mf.addEventListener(
  'keydown',
  (ev) => {
    if (ev.key === '\\') {
      ev.preventDefault();
      mf.executeCommand(['insert', '\\backslash']);
    } else if (ev.key === 'Escape') ev.preventDefault();
  },
  { capture: true }
);

await customElements.whenDefined('math-field');
const locale = MathfieldElement.locale;
console.log("Locale:", locale);
console.log(MathfieldElement.strings[locale.substring(0, 2)]);

<math-field id='formula'>
    x=\frac{-b\pm \sqrt{b^2-4ac}}{2a}
</math-field>

await customElements.whenDefined('math-field');
MathfieldElement.decimalSeparator = ",";

<math-field id='formula'>
    x=\frac{-b\pm \sqrt{b^2-4ac}}{2a}
</math-field>

await window.customElements.whenDefined('math-field');
MathfieldElement.fractionNavigationOrder = "denominator-numerator";

<math-field>
    x=\frac{-b\pm \sqrt{b^2-4ac}}{2a}
</math-field>

Fonts

The content of the mathfield is displayed using a family of high-quality fonts based on the original Computer Modern font from TeX. The mathfield will not display correctly using another font.

By default, the directory containing the fonts is located next to the file containing the mathlive library. If your bundler or asset management system require a different configuration you can specify where the fonts can be located using the MathfieldElement.fontsDirectory property.

await window.customElements.whenDefined("math-field");
MathfieldElement.fontsDirectory = "//unpkg.com/mathlive/dist/fonts/";

<math-field>
    x=\frac{-b\pm \sqrt{b^2-4ac}}{2a}
</math-field>