pbwest 2002/06/04 06:30:23
Added: docs/design/alt.design user-agent-refs.xml
Log:
User agent references in XSL
Revision Changes Path
1.1 xml-fop/docs/design/alt.design/user-agent-refs.xml
Index: user-agent-refs.xml
===================================================================
<?xml version="1.0" encoding="ISO-8859-1"?>
<!-- $Id: user-agent-refs.xml,v 1.1 2002/06/04 13:30:23 pbwest Exp $ -->
<!--
<!DOCTYPE document SYSTEM "../../xml-docs/dtd/document-v10.dtd">
-->
<document>
<header>
<title>User agent refs</title>
<authors>
<person name="Peter B. West" email="[EMAIL PROTECTED]"/>
</authors>
</header>
<body>
<s1 title="User Agent references in XSLFO">
<s2 title="4.9.2 Viewport Geometry">
<p>
If the block-progression-dimension of the reference-area is
larger than that of the viewport-area and the overflow trait
for the reference-area is scroll, then the
inline-scroll-amount and block-scroll-amount are determined
by a scrolling mechanism, if any, provided by the
<strong>user agent</strong>. Otherwise, both are zero.
</p>
</s2>
<s2 title="5.1.3 Actual Values">
<p>
A computed value is in principle ready to be used, but a
user agent may not be able to make use of the value in a
given environment. For example, a <strong>user
agent</strong> may only be able to render borders with
integer pixel widths and may, therefore, have to adjust the
computed width to an integral number of media pixels.
</p>
</s2>
<s2 title="5.5.7 Font Properties">
<p>
There is no XSL mechanism to specify a particular font;
instead, a selected font is chosen from the fonts available
to the <strong>User Agent</strong> based on a set of
selection criteria. The selection criteria are the following
font properties: "font-family", "font-style",
"font-variant", "font-weight", "font-stretch", and
"font-size", plus, for some formatting objects, one or more
characters.
</p>
</s2>
<s2 title="5.9.13.1 Pixels">
<p>
If the <strong>User Agent</strong> chooses a measurement for
a 'px' that does not match an integer number of device dots
in each axis it may produce undesirable effects...
</p>
</s2>
<s2 title="5.10.4 Property Value Functions">
<s3 title="Function: object merge-property-values( NCName)">
<p>
The merge-property-values function returns a value of the
property whose name matches the argument, or if omitted
for the property for which the expression is being
evaluated. The value returned is the specified value on
the last fo:multi-property-set, of the parent
fo:multi-properties, that applies to the <strong>User
Agent</strong> state. If there is no such value, the
computed value of the parent fo:multi-properties is
returned...
</p>
<p>
The test for applicability of a <strong>User
Agent</strong> state is specified using the "active-state"
property.
</p>
</s3>
</s2>
<s2 title="6.3 Formatting Objects Summary">
<s3 title="multi-property-set">
<p>
The fo:multi-property-set is used to specify an
alternative set of formatting properties that, dependent
on a <strong>User Agent</strong> state, are applied to the
content.
</p>
</s3>
<s3 title="title">
<p>
The fo:title formatting object is used to associate a
title with a given page-sequence. This title may be used
by an interactive <strong>User Agent</strong> to identify
the pages. For example, the content of the fo:title can be
formatted and displayed in a "title" window or in a "tool
tip".
</p>
</s3>
</s2>
<s2 title="6.4.1.2 Page-masters">
<p>
... When pages are used with a <strong>User Agent</strong>
such as a Web browser, it is common that the each document
has only one page. The viewport used to view the page
determines the size of the page. When pages are placed on
non-interactive media, such as sheets of paper, pages
correspond to one or more of the surfaces of the paper.
</p>
</s2>
<s2 title="6.4.20 fo:title">
<s3 title="Common Usage:">
<p>
... This title may be used by an interactive <strong>User
Agent</strong> to identify the pages.
</p>
</s3>
</s2>
<s2 title="6.6.3 fo:character">
<s3 title="Constraints:">
<p>
The dimensions of the areas are determined by the font
metrics for the glyph.
</p>
<p>
When formatting an fo:character with a
"treat-as-word-space" value of "true", the <strong>User
Agent</strong> may use a different method for determining
the inline-progression-dimension of the area.
</p>
</s3>
</s2>
<s2 title="6.9 Dynamic Effects: Link and Multi Formatting
Objects">
<s3 title="6.9.1 Introduction">
<p>
Dynamic effects, whereby user actions (including
<strong>User Agent</strong> state) can influence the
behavior and/or representation of portions of a document,
can be achieved through the use of the formatting objects
included in this section:
</p>
<ul>
<li>One-directional single-target links.</li>
<li>
The ability to switch between the display of two or more
formatting object subtrees. This can be used for, e.g.,
expandable/collapsible table of contents, display of an
icon or a full table or graphic.
</li>
<li>
The ability to switch between different property values,
such as color or font-weight, depending on a
<strong>User Agent</strong> state, such as "hover".
</li>
</ul>
</s3>
</s2>
<s2 title="6.10 Out-of-Line Formatting Objects">
<s3 title="6.10.1.3 Conditional Sub-Regions">
<p>
... There may be limits on how much space conditionally
generated areas can borrow from the
region-reference-area. It is left to the <strong>user
agent</strong> to decide these limits.
</p>
<p>
... An interactive <strong>user agent</strong> may choose
to create "hot links" to the footnotes from the
footnote-citation, or create "hot links" to the
before-floats from an implicit citation, instead of
realizing conditional sub-regions.
</p>
</s3>
</s2>
<s2 title="6.10.2 fo:float">
<s3 title="Constraints:">
<p>
... The <strong>user agent</strong> may make its own
determination, after taking into account the intrusion
adjustments caused by one or more overlapping side-floats,
that the remaining space in the
inline-progression-direction is insufficient for the next
side-float or normal block-area. The <strong>user
agent</strong> may address this by causing the next
side-float or normal block-area to "clear" one of the
relevant side-floats, as described in the "clear" property
description, so the intrusion adjustment is sufficiently
reduced. Of the side-floats that could be cleared to meet
this constraint, the side-float that is actually cleared
must be the one whose after-edge is closest to the
before-edge of the parent reference-area.
</p>
<p>
The <strong>user agent</strong> may determine sufficiency
of space by using a fixed length, or by some heuristic
such as whether an entire word fits into the available
space, or by some combination, in order to handle text and
images.
</p>
</s3>
</s2>
<s2 title="6.10.3 fo:footnote">
<s3 title="Constraints:">
<p>
... The second block-area and any additional block-areas
returned by an fo:footnote must be placed on the
immediately subsequent pages to the page containing the
first block-area returned by the fo:footnote, before any
other content is placed. If a subsequent page does not
contain a region-body, the <strong>user agent</strong>
must use the region-master of the last page that did
contain a region-body to hold the additional block-areas.
</p>
</s3>
</s2>
<s2 title="7.3 Reference Rectangle for Percentage Computations">
<p>...</p>
<s3 title="Exceptions ...">
<p>
5. When the absolute-position is "fixed", the containing
block is defined by the nearest ancestor viewport area. If
there is no ancestor viewport area, the containing block
is defined by the <strong>user agent</strong>.
</p>
</s3>
</s2>
<s2 title=
'7.6.5 "pause-after" 7.6.6 "pause-before" 7.6.17 "voice-family"'>
<p>Initial: depends on <strong>user agent</strong></p>
</s2>
<s2 title='7.7.1 "background-attachment"'>
<s3 title="fixed">
<p>
... <strong>User agents</strong> may treat fixed as
scroll. However, it is recommended they interpret fixed
correctly, at least for the HTML and BODY elements, since
there is no way for an author to provide an image only for
those browsers that support fixed.
</p>
</s3>
</s2>
<s2 title='7.7.9 "border-before-width"'>
<s3 title="<length-conditional>">
<p>
... If border-before-width is specified using one of the
width keywords the .conditional component is set to
"discard" and the .length component to a <strong>User
Agent</strong> dependent length.
</p>
</s3>
</s2>
<s2 title='7.7.19 "border-top-color"'>
<s3 title="<color>">
<p>
... If an element's border color is not specified with a
"border" property, <strong>user agents</strong> must use
the value of the element's "color" property as the
computed value for the border color.
</p>
</s3>
</s2>
<s2 title='7.7.20 "border-top-style"'>
<p>
Conforming HTML <strong>user agents</strong> may interpret
'dotted', 'dashed', 'double', 'groove', 'ridge', 'inset',
and 'outset' to be 'solid'.
</p>
</s2>
<s2 title='7.7.21 "border-top-width"'>
<s3 title="thin ... medium ... thick ...">
<p>
... The interpretation of the first three values depends
on the <strong>user agent</strong>.
</p>
</s3>
</s2>
<s2 title='7.8.2 "font-family"'>
<p>Initial: depends on <strong>user agent</strong></p>
</s2>
<s2 title='7.8.3 "font-selection-strategy"'>
<p>
There is no XSL mechanism to specify a particular font;
instead, a selected font is chosen from the fonts available
to the <strong>User Agent</strong> based on a set of
selection criteria. The selection criteria are the following
font properties: "font-family", "font-style",
"font-variant", "font-weight", "font-stretch", and
"font-size", plus, for some formatting objects, one or more
characters.
</p>
<p>
... This fallback may be to seek a match using a
<strong>User Agent</strong> default "font-family", or it may
be a more elaborate fallback strategy where, for example,
"Helvetica" would be used as a fallback for "Univers".
</p>
<p>
If no match has been found for a particular character, there
is no selected font and the <strong>User Agent</strong>
should provide a visual indication that a character is not
being displayed (for example, using the 'missing character'
glyph).
</p>
</s2>
<s2 title='7.8.4 "font-size"'>
<s3 title="<absolute-size>">
<p>
An <absolute-size> keyword refers to an entry in a
table of font sizes computed and kept by the <strong>user
agent</strong>. Possible values are:<br/>[ xx-small |
x-small | small | medium | large | x-large | xx-large ]
</p>
</s3>
<s3 title="<relative-size>">
<p>
A <relative-size> keyword is interpreted relative to
the table of font sizes and the font size of the parent
element. Possible values are:<br/>[ larger | smaller
]<br/>For example, if the parent element has a font size
of "medium", a value of "larger" will make the font size
of the current element be "large". If the parent element's
size is not close to a table entry, the <strong>user
agent</strong> is free to interpolate between table
entries or round off to the closest one. The <strong>user
agent</strong> may have to extrapolate table values if the
numerical value goes beyond the keywords.
</p>
</s3>
<s3 title="<length>">
<p>
A length value specifies an absolute font size (that is
independent of the <strong>user agent</strong>'s font
table).
</p>
</s3>
</s2>
<s2 title='7.8.8 "font-variant"'>
<s3 title="small-caps">
<p>
... If a genuine small-caps font is not available,
<strong>user agents</strong> should simulate a small-caps
font...
</p>
</s3>
</s2>
<s2 title='7.8.9 "font-weight"'>
<s3 title="XSL modifications to the CSS definition:">
<p>
... The association of other weights within a family to
the numerical weight values is intended only to preserve
the ordering of weights within that family. <strong>User
agents</strong> must map names to values in a way that
preserves visual order; a face mapped to a value must not
be lighter than faces mapped to lower values. There is no
guarantee on how a <strong>user agent</strong> will map
fonts within a family to weight values. However, the
following heuristics...
</p>
</s3>
</s2>
<s2 title='7.13.1 "alignment-adjust"'>
<s3 title="auto">
<p>
... If the baseline-identifier does not exist in the
baseline-table for the glyph or other inline-area, then
the <strong>User Agent</strong> may either use heuristics
to determine where that missing baseline would be or may
use the dominant-baseline as a fallback.
</p>
</s3>
</s2>
<s2 title='7.13.3 "baseline-shift"'>
<s3 title="sub/super">
<p>
... Because in most fonts the subscript position is
normally given relative to the "alphabetic" baseline, the
<strong>User Agent</strong> may compute the effective
position for sub/superscripts <em>[sub: spec typo!]</em>
when some other baseline is dominant. ... If there is no
applicable font data the <strong>User Agent</strong> may
use heuristics to determine the offset.
</p>
</s3>
</s2>
<s2 title='7.13.5 "dominant-baseline"'>
<p>
... If there is no baseline-table in the nominal font or if
the baseline-table lacks an entry for the desired baseline,
then the <strong>User Agent</strong> may use heuristics to
determine the position of the desired baseline.
</p>
</s2>
<s2 title='7.14.11 "scaling-method"'>
<s3 title="auto">
<p>
The <strong>User Agent</strong> is free to choose either
resampling, integer scaling, or any other scaling method.
</p>
</s3>
<s3 title="integer-pixels">
<p>
The <strong>User Agent</strong> should scale the image
such that each pixel in the original image is scaled to
the nearest integer number of device-pixels that yields an
image less-then-or-equal-to the image size derived from
the content-height, content-width, and scaling properties.
</p>
</s3>
<s3 title="resample-any-method">
<p>
The <strong>User Agent</strong> should resample the
supplied image to provide an image that fills the size
derived from the content-height, content-width, and
scaling properties. The <strong>user agent</strong> may
use any sampling method.
</p>
</s3>
<p>
... This is defined as a preference to allow the
<strong>user agent</strong> the flexibility to adapt to
device limitations and to accommodate over-constrained
situations involving min/max dimensions and scale factors.
</p>
</s2>
<s2 title='7.14.12 "width"'>
<p>
... The width of a replaced element's box is intrinsic and
may be scaled by the <strong>user agent </strong> if the
value of this property is different than 'auto'.
</p>
</s2>
<s2 title='7.15.4 "line-height"'>
<s3 title="normal">
<p>
Tells <strong>user agents</strong> to set the computed
value to a "reasonable" value based on the font size of
the element.
</p>
</s3>
<p>
... When an element contains text that is rendered in more
than one font, <strong>user agents</strong> should determine
the "line-height" value according to the largest font size.
</p>
</s2>
<s2 title='7.15.9 "text-align"'>
<p>
... The actual justification algorithm used is <strong>user
agent</strong> and written language dependent.<br/>
Conforming <strong>user agents</strong> may interpret the
value 'justify' as 'left' or 'right', depending on whether
the element's default writing direction is left-to-right or
right-to-left, respectively.
</p>
</s2>
<s2 title='7.15.11 "text-indent"'>
<p>
... <strong>User agents</strong> should render this
indentation as blank space.
</p>
</s2>
<s2 title='7.16.2 "letter-spacing"'>
<s3 title="normal">
<p>
The spacing is the normal spacing for the current
font. This value allows the <strong>user agent</strong> to
alter the space between characters in order to justify
text.
</p>
</s3>
<s3 title="<length>">
<p>
This value indicates inter-character space in addition to
the default space between characters. Values may be
negative, but there may be implementation-specific
limits. <strong>User agents</strong> may not further
increase or decrease the inter-character space in order to
justify text.
</p>
</s3>
<p>
Character-spacing algorithms are <strong>user agent</strong>
dependent. Character spacing may also be influenced by
justification (see the "text-align" property).<br/> When the
resultant space between two characters is not the same as
the default space, <strong>user agents</strong> should not
use ligatures.<br/> Conforming <strong>user agents</strong>
may consider the value of the 'letter-spacing' property to
be 'normal'.
</p>
<s3 title="XSL modifications to the CSS definition:">
<p>
... For "normal": .optimum = "the normal spacing for the
current font" / 2, .maximum = auto, .minimum = auto,
.precedence = force, and .conditionality = discard. A
value of auto for a component implies that the limits are
<strong>User Agent</strong> specific.
</p>
<p>
... The CSS statement that "Conforming <strong>user
agents</strong> may consider the value of the
'letter-spacing' property to be 'normal'." does not apply
in XSL, if the <strong>User Agent</strong> implements the
"Extended" property set.
</p>
<p>
... The algorithm for resolving the adjusted values
between word spacing and letter spacing is <strong>User
Agent</strong> dependent.
</p>
</s3>
</s2>
<s2 title='7.16.4 "text-decoration"'>
<p>
... If the element has no content or no text content (e.g.,
the IMG element in HTML), <strong>user agents</strong> must
ignore this property.
</p>
<s3 title="blink">
<p>
... Conforming <strong>user agents</strong> are not
required to support this value.
</p>
</s3>
</s2>
<s2 title='7.16.6 "text-transform"'>
<p>
... Conforming <strong>user agents</strong> may consider the
value of "text-transform" to be "none" for characters that
are not from the ISO Latin-1 repertoire and for elements in
languages for which the transformation is different from
that specified by the case-conversion tables of Unicode or
ISO 10646.
</p>
</s2>
<s2 title='7.16.8 "word-spacing"'>
<p>
... Word spacing algorithms are <strong>user
agent</strong>-dependent.
</p>
<s3 title="XSL modifications to the CSS definition:">
<p>
... The algorithm for resolving the adjusted values
between word spacing and letter spacing is <strong>User
Agent</strong> dependent.
</p>
</s3>
</s2>
<s2 title='7.17.1 "color"'>
<p>Initial: depends on <strong>user agent</strong></p>
</s2>
<s2 title='7.17.3 "rendering-intent"'>
<s3 title="auto">
<p>
This is the default behavior. The <strong>User
Agent</strong> determines the best intent based on the
content type. For image content containing an embedded
profile, it shall be assumed that the intent specified
within the profile is the desired intent. Otherwise, the
<strong>user agent</strong> shall use the current profile
and force the intent, overriding any intent that might be
stored in the profile itself.
</p>
</s3>
</s2>
<s2 title='7.20.2 "overflow"'>
<s3 title="scroll">
<p>
This value indicates that the content is clipped and that
if the <strong>user agent</strong> uses a scrolling
mechanism that is visible on the screen (such as a scroll
bar or a panner), that mechanism should be displayed for a
box whether or not any of its content is clipped.
</p>
</s3>
<s3 title="auto">
<p>
The behavior of the "auto" value is <strong>user
agent</strong> dependent, but should cause a scrolling
mechanism to be provided for overflowing boxes.
</p>
</s3>
</s2>
<s2 title='7.21.2 "leader-pattern"'>
<s3 title="dots">
<p>
... The choice of dot character is dependent on the
<strong>user agent</strong>.
</p>
</s3>
</s2>
<s2 title='7.21.4 "leader-length"'>
<p>
... <strong>User agents</strong> may choose to use the value
of "leader-length.optimum" to determine where to break the
line, then use the minimum and maximum values during line
justification.
</p>
</s2>
<s2 title='7.25.11 "media-usage"'>
<s3 title="auto">
<p>
The <strong>User Agent</strong> determines which value of
"media-usage" (other than the "auto" value) is used. The
<strong>User Agent</strong> may consider the type of media
on which the presentation is to be placed in making this
determination.<br/> NOTE:<br/> For example, the
<strong>User Agent </strong> could use the following
decision process. If the media is not continuous and is of
fixed bounded size, then the "paginate" (described below)
is used. Otherwise, the "bounded-in-one-dimension" is
used.
</p>
</s3>
<s3 title="bounded-in-one-dimension">
<p>
... It is an error if more or less than one of
"page-height" or "page-width" is specified on the first
page master that is used. The <strong>User Agent</strong>
may recover as follows:...
</p>
</s3>
<s3 title="unbounded">
<p>
Only one page is generated per fo:page-sequence descendant
from the fo:root. Neither "page-height" nor "page-width"
may be specified on any page master that is used. If a
value is specified for either property, it is an error and
a <strong>User Agent</strong> may recover by ignoring the
specified value. ...
</p>
</s3>
</s2>
<s2 title='7.25.13 "page-height"'>
<s3 title="auto">
<p>
The "page-height" shall be determined, in the case of
continuous media, from the size of the <strong>User
Agent</strong> window...
</p>
</s3>
<s3 title="NOTE:">
<p>
A <strong>User Agent</strong> may provide a way to declare
the media for which formatting is to be done. This may be
different from the media on which the formatted result is
viewed. For example, a browser <strong>User Agent</strong>
may be used to preview pages that are formatted for sheet
media. In that case, the size calculation is based on the
media for which formatting is done rather than the media
being currently used.
</p>
</s3>
</s2>
<s2 title='7.25.15 "page-width"'>
<s3 title="auto">
<p>
The "page-width" shall be determined, in the case of
continuous media, from the size of the <strong>User
Agent</strong> window...
</p>
</s3>
</s2>
<s2 title='7.26.5 "border-separation"'>
<s3 title="<length-bp-ip-direction>">
<p>
... Rows, columns, row groups, and column groups cannot
have borders (i.e., <strong>user agents</strong> must
ignore the border properties for those elements).
</p>
</s3>
</s2>
<s2 title='7.26.7 "caption-side"'>
<p>
... For a caption that is on the left or right side of a
table box, on the other hand, a value other than "auto" for
"width" sets the width explicitly, but "auto" tells the
<strong>user agent</strong> to chose a "reasonable width".
</p>
</s2>
<s2 title='7.27.2 "glyph-orientation-horizontal"'>
<s3 title="<angle>">
<p>
... The <strong>User Agent</strong> shall round the value
of the angle to the closest of the permitted values.
</p>
</s3>
</s2>
<s2 title='7.27.3 "glyph-orientation-vertical"'>
<s3 title="auto">
<p>
... The determination of which characters should be
auto-rotated may vary across <strong>User Agents</strong>.
</p>
</s3>
<s3 title="<angle>">
<p>
... The <strong>User Agent</strong> shall round the value
of the angle to the closest of the permitted values.
</p>
</s3>
</s2>
<s2 title='7.27.6 "unicode-bidi"'>
<s3 title="XSL modifications to the CSS definition:">
<p>
... Fallback:<br/> If it is not possible to present the
characters in the correct order, then the
<strong>UserAgent </strong> should display either a
'missing character' glyph or display some indication that
the content cannot be correctly rendered.
</p>
</s3>
</s2>
<s2 title='7.28.1 "content-type"'>
<p>
... This property specifies the content-type and may be used
by a <strong>User Agent</strong> to select a rendering
processor for the object.
</p>
<s3 title="auto">
<p>
No identification of the content-type. The <strong>User
Agent</strong> may determine it by "sniffing" or by other
means.
</p>
</s3>
</s2>
<s2 title='7.29.5 "border-color"'>
<p>
... If an element's border color is not specified with a
"border" property, <strong>user agents</strong> must use the
value of the element's "color" property as the computed
value for the border color.
</p>
</s2>
<s2 title='7.29.9 "border-spacing"'>
<p>
... Rows, columns, row groups, and column groups cannot have
borders (i.e., <strong>user agents</strong> must ignore the
border properties for those elements).
</p>
</s2>
<s2 title='7.29.13 "font"'>
<p>
... If no font with the indicated characteristics exists on
a given platform, the <strong>user agent</strong> should
either intelligently substitute (e.g., a smaller version of
the "caption" font might be used for the "small-caption"
font), or substitute a <strong>user agent</strong> default
font.
</p>
</s2>
<s2 title='7.29.19 "pause"'>
<p>Initial: depends on <strong>user agent</strong></p>
</s2>
<s2 title='7.29.21 "size"'>
<p>
... Relative page boxes allow <strong>user agents</strong>
to scale a document and make optimal use of the target size.
</p>
<p>
... <strong>User agents</strong> may allow users to control
the transfer of the page box to the sheet (e.g., rotating an
absolute page box that's being printed).
</p>
<ul>
<li>
Rendering page boxes that do not fit a target sheet<br/>
If a page box does not fit the target sheet dimensions,
the <strong>user agent</strong> may choose to:
<ul>
<li>
Rotate the page box 90 degrees if this will make the
page box fit.
</li>
<li>Scale the page to fit the target.</li>
</ul>
The <strong>user agent</strong> should consult the user
before performing these operations.
</li>
<li>
Positioning the page box on the sheet<br/> When the page
box is smaller than the target size, the <strong>user
agent</strong> is free to place the page box anywhere on
the sheet.
</li>
</ul>
</s2>
<s2 title='7.29.23 "white-space"'>
<s3 title="normal">
<p>
This value directs <strong>user agents</strong> to
collapse sequences of whitespace, and break lines as
necessary to fill line boxes. ...
</p>
</s3>
<s3 title="pre">
<p>
This value prevents <strong>user agents</strong> from
collapsing sequences of whitespace. ...
</p>
</s3>
<p>
... Conforming <strong>user agents</strong> may ignore the
'white-space' property in author and user style sheets but
must specify a value for it in the default style sheet.
</p>
</s2>
</s1>
</body>
</document>
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