@Section
   @Title { Underlining }
   @Tag { underlining }
@Begin
@PP
The @Code "@Underline" symbol underlines the following object:
underline.sym @Index @Code "@Underline"
@ID @OneRow @Code {
"This little paragraph of text will have"
"@Underline { three underlined words } in it."
}
produces
@ID @OneRow 1.6i @Wide {
This little paragraph of text will have
@Underline { three underlined words } in it.
}
The underlining is continuous unless a line break intervenes.  You
can't use this symbol to underline an arbitrary object:  it is carefully
designed to produce high-quality underlining of single words and
parts of paragraphs, and it works only for those objects.
@PP
Each font contains information about how words in that font should be
underlined:  how far below the baseline the line should be drawn, and how
thick.  The @Code "@Underline" symbol uses this information; the font
it bases its underlining on is the font of the first object underlined
if it is a word, or else the font of the enclosing paragraph.
@PP
The underline produced by @Code "@Underline" will have the same colour
as whatever is being underlined.  If you want a different colour, you need
the @Code "@ColouredUnderline" or equivalently @Code "@ColoredUnderline"
symbol, which takes a colour on the left as well as the thing to be
underlined on the right:
@ID @OneRow @Code {
"This little paragraph of text will have"
"blue @ColouredUnderline { three underlined words } in it."
}
produces
@ID @OneRow 1.6i @Wide {
This little paragraph of text will have
blue @ColouredUnderline { three underlined words } in it.
}
The colours available are as for the @Code "@Colour" symbol from
Section {@NumberOf colour}.
@PP
There is no way to set a default value for the colour of a coloured
underline, but you can make it easy to get an underline of a specific
colour, by placing a definition at the start of your document, like this:
@ID @OneRow @Code @Verbatim {
import @BasicSetup
def @MustCheck right x { blue @ColouredUnderline x }
}
This allows you to type @Code "@MustCheck" instead of
{@Code "blue @ColouredUnderline"}.  Definitions are explained in
general in Section {@NumberOf definitions}.
@End @Section
