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Values - MathML 编辑

Lengths

Several MathML presentation elements have attributes that accept length values used for size or spacing. MathML accepts different units and constants for specifying lengths.

Units

Unit	Description
`em`	`font-relative` unit
`ex`	`font-relative` unit. (The "x"-height of the element, `1ex ≈ 0.5em` in many fonts)
`px`	Pixels
`in`	Inches (1 inch = 2.54 centimeters)
`cm`	Centimeters
`mm`	Millimeters
`pt`	Points (1 point = 1/72 inch)
`pc`	Picas (1 pica = 12 points)
`%`	Percentage of the default value.

This feature is no longer recommended. Though some browsers might still support it, it may have already been removed from the relevant web standards, may be in the process of being dropped, or may only be kept for compatibility purposes. Avoid using it, and update existing code if possible; see the compatibility table at the bottom of this page to guide your decision. Be aware that this feature may cease to work at any time.

A replacement for the deprecated constants below is:

veryverythinmathspace  => 0.05555555555555555em
verythinmathspace      => 0.1111111111111111em
thinmathspace          => 0.16666666666666666em
mediummathspace        => 0.2222222222222222em
thickmathspace         => 0.2777777777777778em
verythickmathspace     => 0.3333333333333333em
veryverythickmathspace => 0.3888888888888889em

Constant	Value
`veryverythinmathspace`	1/18`em`
`verythinmathspace`	2/18`em`
`thinmathspace`	3/18`em`
`mediummathspace`	4/18`em`
`thickmathspace`	5/18`em`
`verythickmathspace`	6/18`em`
`veryverythickmathspace`	7/18`em`
Negative contstants are introduced in Gecko 7.0 (Firefox 7.0 / Thunderbird 7.0 / SeaMonkey 2.4) (bug 650530)
`negativeveryverythinmathspace`	-1/18`em`
`negativeverythinmathspace`	-2/18`em`
`negativethinmathspace`	-3/18`em`
`negativemediummathspace`	-4/18`em`
`negativethickmathspace`	-5/18`em`
`negativeverythickmathspace`	-6/18`em`
`negativeveryverythickmathspace`	-7/18`em`