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diff --git a/docs/design/alt.design/user-agent-refs.xml b/docs/design/alt.design/user-agent-refs.xml new file mode 100644 index 000000000..19a199c68 --- /dev/null +++ b/docs/design/alt.design/user-agent-refs.xml @@ -0,0 +1,806 @@ +<?xml version="1.0" encoding="ISO-8859-1"?> +<!-- $Id$ --> +<!-- +<!DOCTYPE document SYSTEM "../../xml-docs/dtd/document-v10.dtd"> +--> + +<document> + <header> + <title>User agent refs</title> + <authors> + <person name="Peter B. West" email="pbwest@powerup.com.au"/> + </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> |