By the help of this dialog it is possible to attach color attributes to different kinds of hypertext elements that are displayed by a viewer window. Any settings made and accepted here have an immediate effect on all subsequent displays.
A color attribute consists of a background color index and a
foreground color index, where each color index points to an entry
of the palette of 16 RGB colors of that screen
on which the hypertext elements are actually displayed (see also the dialog
"Screen Settings"). A color index is represented by
a single hexadecimal digit and is expressed using the characters
0-9 and A-F.
Each color attribute (a) that is to be specified here is just the concatenation of a background (b) and foreground (f) color index:
a = bf
Hypertext elements may be nested according to the rules of the underlying
markup language (e.g. HTML), so that inner elements (closer to a
character) are able to (and usually will) override effects of outer
elements in a destructive manner during display. In order to allow the
background and/or foreground color of particular elements to be transparent
and hence affected by enclosing elements, a hyphen (-) may be
specified instead of a valid color index for this purpose. A special handling
occurs for link-like elements (Link and vLink),
which does only allow the transparent part of their color attribute to be
overridden again by an enclosed element.
Alternatively and intended for advanced usage, it is possible to specify a
bitmask of those bits of a color attribute that are to be set by an
element, while the remaining bits are left unchanged. A bitmask is given by
appending it, separated by a slash (/), as a hexadecimal value
to the color attribute of an element.
In the following list, all types of elements to which a color attribute can be attached are given together with their default value:
70 or 70/ff)This is the standard (outermost) color attribute that applies to all elements if not otherwise overridden.
-- or 70/00)Heading title elements such as <h1> to
<h6> are covered by this attribute.
-4 or 74/0f)Hyperlinks of any sort such as <a>, <area>
and other generated links, e.g. <frame>, fall into this
category.
-5 or 75/0f)Color attribute for visited hyperlinks that are otherwise covered by Link.
8f or 8f/ff)Specifies the color attribute for all kinds of
form elements that are generated from
<input> elements.
-6 or 76/0f)Color attribute for inline images such as <img>
elements.
-1 or 71/0f)Color attribute for <em>, <i>,
<var>, <cite> and <u>
elements.
-1 or 71/0f)Color attribute for <strong>, <b>
and <dfn> elements.
f- or f0/f0)Color attribute for <code>, <tt>,
<samp> and <kbd> elements.
<pre> and similar block elements are not affected per
se.
-1 or 71/0f)Color attribute for <th> elements.
The information about visited hyperlinks (a list of URLs without fragments) is maintained by a function that is part of a request context and is not shared between different request contexts. If a cache is in use, it is also used to provide the relevant information.