CSS GUIDE FONT-SIZE-ADJUST

Summary

A factor contributing to the legibility of fonts at different sizes is the relationship between the height of the 'font-size' and the height of the font's x-height (the height of its lowercase letter 'x'.) The ratio between these two factors ('font-size' divided by x-height) is called a font's "aspect value." If an aspect value ratio is large for a font, it is more likely to be legible at a given font-size than a font with a smaller aspect value.

The font-size-adjust property allows authors to specify the "aspect value" that they wish to maintain. It becomes helpful when a specified font is unavailable and the system needs hints to determine the most suitable substitute.

Syntax

h5.med  { font-size-adjust: number | none }

Legal Values

inherit

• Explicitly sets the value of this property to that of the parent.

none

• Do not preserve the current specified font's x-height if the font is not available.

number

• Specifies the Aspect Value ratio for the font. The formula for determining the appropriate font size for an available font is:

 ['font-size']*(['font-size-adjust']/[aspect value of available font]) = [font size to use]

Usage Examples

Ext/Doc: h5.med  { font-size-adjust: 0.58 }
In-Line:  <h5 STYLE="font-size-adjust: 0.58">text</h5>

Notes

• Child elements inherit 'un-adjusted' font-size values.
• The CSS2 spec states that a 'font-size-adjust' number value indicates the aspect value of the first-choice font. No mention is made of what should happen if the actual aspect value of the indicated font conflicts with the given aspect value.