Allow global configuration of the scale of visually rendered text content. Preserve distinctions in the size of rendered text as the user increases or decreases the scale.
As part of satisfying provision one of this checkpoint, provide a configuration option to override rendered text sizes specified by the author or user agent defaults.
As part of satisfying provision one of this checkpoint, offer a range of text sizes to the user that includes at least:
the range offered by the conventional utility available in the operating environment that allows users to choose the text size (e.g., the font size), or
if no such utility is available, the range of text sizes supported by the conventional APIs of the operating environment for drawing text.
Sufficient techniques
The user agent may satisfy provision one of this checkpoint through a number of mechanisms, including zoom, magnification, and allowing the user to configure a reference size for rendered text (e.g., render text at 36 points unless otherwise specified). For example, for CSS2 [CSS2] user agents, the medium value of the font-size property corresponds to a reference size.
Normative inclusions and exclusions
The word "scale" is used in this checkpoint to mean the general size of text.
The user agent is not required to satisfy this requirement through proportional scaling. What must hold is that if rendered text A is smaller than rendered text B at one value of the configuration setting of provision one, then text A will still be smaller than text B at another value of this configuration setting.