dominant-baseline - SVG 编辑

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The dominant-baseline attribute is used to determine or re-determine a scaled-baseline-table. A scaled-baseline-table is a compound value with three components: a baseline-identifier for the dominant-baseline, a baseline-table and a baseline-table font-size. Some values of the property re-determine all three values; other 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 desire scaled-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.

As a presentation attribute, it also can be used as a property directly inside a CSS stylesheet, see css dominant-baseline for further information.

Usage context

auto

If this property occurs on 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, else if the writing-mode is vertical, then the value of the dominant-baseline component is central. 

If this property occurs on a <tspan>, <tref>, <altGlyph> 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 above for <text> elements.

use-script

The dominant-baseline and the baseline-table components are set by determining the predominant script of the character data content. The writing-mode, whether horizontal or vertical, is used to select the appropriate set of baseline-tables and the dominant baseline is used to select the baseline-table that corresponds to that baseline. 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.

no-change

The dominant-baseline, the baseline-table, and the baseline-table font-size remain the same as that of the parent text content element.

reset-size

The dominant-baseline and the baseline-table remain the same, but the baseline-table font-size is changed to the value of the font-size attribute on this element. This re-scales the baseline-table for the current font-size.

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 font-size attribute on this element.

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 font-size attribute on this element.

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 attribute on this element.

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 font-size attribute on this element.

central

The baseline-identifier for the dominant-baseline is set to be central. 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 font-size attribute on this element.

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: alphabetic, ideographic, hanging, mathematical. The baseline-table font-size is changed to the value of the font-size attribute on this element.

text-after-edge

The baseline-identifier for the dominant-baseline is set to be text-after-edge. The derived baseline-table is constructed from the defined baselines in a baseline-table in the font. The choice of which font baseline-table to use from the baseline-tables in the font is browser dependent. The baseline-table font-size is changed to the value of the font-size attribute on this element.

text-before-edge

The baseline-identifier for the dominant-baseline is set to be text-before-edge. The derived baseline-table is constructed from the defined baselines in a baseline-table in the font. The choice of which baseline-table to use from the baseline-tables in the font is browser dependent. The baseline-table font-size is changed to the value of the font-size attribute on this element.

Example

Elements

The following elements can use the dominant-baseline-shift attribute

• Text content elements »

See also

• css dominant-baseline