dominant-baseline

The dominant-baseline CSS property specifies the specific baseline used to align the box's text and inline-level contents. It also indicates the default alignment baseline of any boxes participating in baseline alignment in the box's alignment context. If present, it overrides the shape's dominant-baseline attribute.

Baselines are selected from the font baseline table. If there is no baseline table in the nominal font, or if the baseline table lacks an entry for the desired baseline, then the browser may use heuristics to determine the position of the desired baseline.

The dominant-baseline property is used to determine or re-determine a scaled-baseline-table. A scaled-baseline-table is a compound value with three components:

  1. a baseline-identifier for the dominant-baseline,
  2. a baseline-table, and
  3. a baseline-table font-size.

Some values of dominant-baseline re-determine all three values. Others only re-establish the baseline-table font-size. When the initial value, auto, would give an undesired result, this property can be used to explicitly set the desired scaled-baseline-table.

Note: The dominant-baseline property only has an effect on the <text>, <textPath>, <tref>, and <tspan> SVG elements.

Syntax

css
/* Initial value */
dominant-baseline: auto;

/* Keyword values */
dominant-baseline: alphabetic;
dominant-baseline: central;
dominant-baseline: hanging;
dominant-baseline: ideographic;
dominant-baseline: mathematical;
dominant-baseline: middle;
dominant-baseline: text-bottom;
dominant-baseline: text-top;

/* Global values */
dominant-baseline: inherit;
dominant-baseline: initial;
dominant-baseline: revert;
dominant-baseline: revert-layer;
dominant-baseline: unset;

Values

auto

If this property is applied to a <text> element, then the computed value depends on the value of the writing-mode attribute.

If the writing-mode is horizontal, then the value of the dominant-baseline component is alphabetic. Otherwise, if the writing-mode is vertical, then the value of the dominant-baseline component is central.

If this property is applied to a <tspan>, <tref>, or <textPath> element, then the dominant-baseline and the baseline-table components remain the same as those of the parent text content element.

If the computed baseline-shift value actually shifts the baseline, then the baseline-table font-size component is set to the value of the font-size attribute on the element on which the dominant-baseline attribute occurs, otherwise the baseline-table font-size remains the same as that of the element.

If there is no parent text content element, the scaled-baseline-table value is constructed as for <text> elements.

alphabetic

The baseline-identifier for the dominant-baseline is set to be alphabetic, the derived baseline-table is constructed using the alphabetic baseline-table in the font, and the baseline-table font-size is changed to the value of the element's font-size SVG attribute or the CSS font-size, if set..

central

The baseline-identifier for the dominant-baseline is set to be central. The derived baseline-table is constructed from the defined baselines in the font's baseline-table. That font baseline-table is chosen using the following priority order of baseline-table names: ideographic, alphabetic, hanging, mathematical. The baseline-table font-size is changed to the value of the element's font-size SVG attribute or the CSS font-size, if set.

hanging

The baseline-identifier for the dominant-baseline is set to be hanging, the derived baseline-table is constructed using the hanging baseline-table in the font, and the baseline-table font-size is changed to the value of the font-size SVG attribute of font-size CSS property on this element.

ideographic

The baseline-identifier for the dominant-baseline is set to be ideographic, the derived baseline-table is constructed using the ideographic baseline-table in the font, and the baseline-table font-size is changed to the value of the value of the element's font-size SVG attribute or the CSS font-size, if set.

mathematical

The baseline-identifier for the dominant-baseline is set to be mathematical, the derived baseline-table is constructed using the mathematical baseline-table in the font, and the baseline-table font-size is changed to the value of the value of the element's font-size SVG attribute or the CSS font-size, if set.

middle

The baseline-identifier for the dominant-baseline is set to be middle. The derived baseline-table is constructed from the defined baselines in a baseline-table in the font. That font baseline-table is chosen using the following priority order of baseline-table names: ideographic, alphabetic, hanging, mathematical. The baseline-table font-size is changed to the value of the element's font-size SVG attribute or the CSS font-size, if set.

text-bottom

The line-under edge is used as the baseline, which is usually the bottom edge of the font's em box.

text-top

The line-over edge is used as the baseline, which is usually the top edge of the font's em box.

Formal definition

Value not found in DB!

Formal syntax

dominant-baseline = 
auto          |
text-bottom   |
alphabetic    |
ideographic   |
middle        |
central       |
mathematical  |
hanging       |
text-top

Example

html
<svg viewBox="0 0 450 160" width="700" height="200">
  <text x="50" y="20">alphabetic</text>
  <text x="50" y="60">central</text>
  <text x="50" y="100">hanging</text>
  <text x="50" y="140">ideographic</text>
  <text x="250" y="20">mathematical</text>
  <text x="250" y="60">middle</text>
  <text x="250" y="100">text-bottom</text>
  <text x="250" y="140">text-top</text>
  <path
    d="M   0,20 l 400,0
       m -400,40 l 400,0
       m -400,40 l 400,0
       m -400,40 l 400,0"
    stroke="grey" />
  <text x="0" y="20" fill="red">auto</text>
  <text x="0" y="60" fill="red">auto</text>
  <text x="0" y="100" fill="red">auto</text>
  <text x="0" y="140" fill="red">auto</text>
</svg>
css
text {
  font-size: 20px;
}
text:nth-of-type(1) {
  dominant-baseline: alphabetic;
}
text:nth-of-type(2) {
  dominant-baseline: central;
}
text:nth-of-type(3) {
  dominant-baseline: hanging;
}
text:nth-of-type(4) {
  dominant-baseline: ideographic;
}
text:nth-of-type(5) {
  dominant-baseline: mathematical;
}
text:nth-of-type(6) {
  dominant-baseline: middle;
}
text:nth-of-type(7) {
  dominant-baseline: text-bottom;
}
text:nth-of-type(8) {
  dominant-baseline: text-top;
}

Specifications

Specification
Scalable Vector Graphics (SVG) 2
# DominantBaselineProperty
CSS Inline Layout Module Level 3
# dominant-baseline-property

Browser compatibility

BCD tables only load in the browser

See also