User agent refs

From 12d67454323295b1bf984190555cc8aa1ce9eeca Mon Sep 17 00:00:00 2001 From: Peter Bernard West Date: Tue, 4 Jun 2002 13:30:23 +0000 Subject: User agent references in XSL git-svn-id: https://svn.apache.org/repos/asf/xmlgraphics/fop/trunk@194852 13f79535-47bb-0310-9956-ffa450edef68 --- docs/design/alt.design/user-agent-refs.xml | 806 +++++++++++++++++++++++++++++ 1 file changed, 806 insertions(+) create mode 100644 docs/design/alt.design/user-agent-refs.xml (limited to 'docs') 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 @@ + + + + + +

+ User agent refs + + + +

+ + + +

+ 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 + user agent. Otherwise, both are zero. +

+ + +

+ 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 user + agent 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. +

+ + +

+ There is no XSL mechanism to specify a particular font; + instead, a selected font is chosen from the fonts available + to the User Agent 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. +

+ + +

+ If the User Agent chooses a measurement for + a 'px' that does not match an integer number of device dots + in each axis it may produce undesirable effects... +

+ + + +

+ 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 User + Agent state. If there is no such value, the + computed value of the parent fo:multi-properties is + returned... +

+ The test for applicability of a User + Agent state is specified using the "active-state" + property. +

+ + + + +

+ The fo:multi-property-set is used to specify an + alternative set of formatting properties that, dependent + on a User Agent state, are applied to the + content. +

+ + +

+ The fo:title formatting object is used to associate a + title with a given page-sequence. This title may be used + by an interactive User Agent 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". +

+ + + +

+ ... When pages are used with a User Agent + 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. +

+ + + +

+ ... This title may be used by an interactive User + Agent to identify the pages. +

+ + + + +

+ The dimensions of the areas are determined by the font + metrics for the glyph. +

+ When formatting an fo:character with a + "treat-as-word-space" value of "true", the User + Agent may use a different method for determining + the inline-progression-dimension of the area. +

+ + + + +

+ Dynamic effects, whereby user actions (including + User Agent 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: +

One-directional single-target links.
+ 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. +
+ The ability to switch between different property values, + such as color or font-weight, depending on a + User Agent state, such as "hover". +

+ + + + +

+ ... There may be limits on how much space conditionally + generated areas can borrow from the + region-reference-area. It is left to the user + agent to decide these limits. +

+ ... An interactive user agent 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. +

+ + + + +

+ ... The user agent 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 user + agent 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. +

+ The user agent 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. +

+ + + + +

+ ... 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 user agent + must use the region-master of the last page that did + contain a region-body to hold the additional block-areas. +

+ + + +

...

+ +

+ 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 user agent. +

+ + + +

Initial: depends on user agent

+ + + +

+ ... User agents 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. +

+ + + + +

+ ... 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 User + Agent dependent length. +

+ + + + +

+ ... If an element's border color is not specified with a + "border" property, user agents must use + the value of the element's "color" property as the + computed value for the border color. +

+ + + +

+ Conforming HTML user agents may interpret + 'dotted', 'dashed', 'double', 'groove', 'ridge', 'inset', + and 'outset' to be 'solid'. +

+ + + +

+ ... The interpretation of the first three values depends + on the user agent. +

+ + + +

Initial: depends on user agent

+ + +

+ ... This fallback may be to seek a match using a + User Agent default "font-family", or it may + be a more elaborate fallback strategy where, for example, + "Helvetica" would be used as a fallback for "Univers". +

+ If no match has been found for a particular character, there + is no selected font and the User Agent + should provide a visual indication that a character is not + being displayed (for example, using the 'missing character' + glyph). +

+ + + +

+ + +

+ A <relative-size> keyword is interpreted relative to + the table of font sizes and the font size of the parent + element. Possible values are:
[ larger | smaller + ]
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 user + agent is free to interpolate between table + entries or round off to the closest one. The user + agent may have to extrapolate table values if the + numerical value goes beyond the keywords. +

+ + +

+ A length value specifies an absolute font size (that is + independent of the user agent's font + table). +

+ + + + +

+ ... If a genuine small-caps font is not available, + user agents should simulate a small-caps + font... +

+ + + + +

+ ... 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. User + agents 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 user agent will map + fonts within a family to weight values. However, the + following heuristics... +

+ + + + +

+ ... If the baseline-identifier does not exist in the + baseline-table for the glyph or other inline-area, then + the User Agent may either use heuristics + to determine where that missing baseline would be or may + use the dominant-baseline as a fallback. +

+ + + + +

+ ... Because in most fonts the subscript position is + normally given relative to the "alphabetic" baseline, the + User Agent may compute the effective + position for sub/superscripts [sub: spec typo!] + when some other baseline is dominant. ... If there is no + applicable font data the User Agent may + use heuristics to determine the offset. +

+ + + +

+ ... If there is no baseline-table in the nominal font or if + the baseline-table lacks an entry for the desired baseline, + then the User Agent may use heuristics to + determine the position of the desired baseline. +

+ + + +

+ The User Agent is free to choose either + resampling, integer scaling, or any other scaling method. +

+ + +

+ The User Agent 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. +

+ + +

+ The User Agent should resample the + supplied image to provide an image that fills the size + derived from the content-height, content-width, and + scaling properties. The user agent may + use any sampling method. +

+ +

+ ... This is defined as a preference to allow the + user agent the flexibility to adapt to + device limitations and to accommodate over-constrained + situations involving min/max dimensions and scale factors. +

+ + +

+ ... The width of a replaced element's box is intrinsic and + may be scaled by the user agent if the + value of this property is different than 'auto'. +

+ + + +

+ Tells user agents to set the computed + value to a "reasonable" value based on the font size of + the element. +

+ +

+ ... When an element contains text that is rendered in more + than one font, user agents should determine + the "line-height" value according to the largest font size. +

+ + +

+ ... The actual justification algorithm used is user + agent and written language dependent.
+ Conforming user agents 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. +

+ + +

+ ... User agents should render this + indentation as blank space. +

+ + + +

+ The spacing is the normal spacing for the current + font. This value allows the user agent to + alter the space between characters in order to justify + text. +

+ + +

+ 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. User agents may not further + increase or decrease the inter-character space in order to + justify text. +

+ +

+ Character-spacing algorithms are user agent + dependent. Character spacing may also be influenced by + justification (see the "text-align" property).
When the + resultant space between two characters is not the same as + the default space, user agents should not + use ligatures.
Conforming user agents + may consider the value of the 'letter-spacing' property to + be 'normal'. +

+ +

+ ... 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 + User Agent specific. +

+ ... The CSS statement that "Conforming user + agents may consider the value of the + 'letter-spacing' property to be 'normal'." does not apply + in XSL, if the User Agent implements the + "Extended" property set. +

+ ... The algorithm for resolving the adjusted values + between word spacing and letter spacing is User + Agent dependent. +

+ + + +

+ ... If the element has no content or no text content (e.g., + the IMG element in HTML), user agents must + ignore this property. +

+ +

+ ... Conforming user agents are not + required to support this value. +

+ + + +

+ ... Conforming user agents 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. +

+ + +

+ ... Word spacing algorithms are user + agent-dependent. +

+ +

+ ... The algorithm for resolving the adjusted values + between word spacing and letter spacing is User + Agent dependent. +

+ + + +

Initial: depends on user agent

+ + + +

+ This is the default behavior. The User + Agent 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 + user agent shall use the current profile + and force the intent, overriding any intent that might be + stored in the profile itself. +

+ + + + +

+ This value indicates that the content is clipped and that + if the user agent 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. +

+ + +

+ The behavior of the "auto" value is user + agent dependent, but should cause a scrolling + mechanism to be provided for overflowing boxes. +

+ + + + +

+ ... The choice of dot character is dependent on the + user agent. +

+ + + +

+ ... User agents 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. +

+ + + +

+ The User Agent determines which value of + "media-usage" (other than the "auto" value) is used. The + User Agent may consider the type of media + on which the presentation is to be placed in making this + determination.
NOTE:
For example, the + User Agent 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. +

+ + +

+ ... 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 User Agent + may recover as follows:... +

+ + +

+ 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 User Agent may recover by ignoring the + specified value. ... +

+ + + + +

+ The "page-height" shall be determined, in the case of + continuous media, from the size of the User + Agent window... +

+ + +

+ A User Agent 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 User Agent + 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. +

+ + + + +

+ The "page-width" shall be determined, in the case of + continuous media, from the size of the User + Agent window... +

+ + + + +

+ ... Rows, columns, row groups, and column groups cannot + have borders (i.e., user agents must + ignore the border properties for those elements). +

+ + + +

+ ... 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 + user agent to chose a "reasonable width". +

+ + + +

+ ... The User Agent shall round the value + of the angle to the closest of the permitted values. +

+ + + + +

+ ... The determination of which characters should be + auto-rotated may vary across User Agents. +

+ + +

+ ... The User Agent shall round the value + of the angle to the closest of the permitted values. +

+ + + + +

+ ... Fallback:
If it is not possible to present the + characters in the correct order, then the + UserAgent should display either a + 'missing character' glyph or display some indication that + the content cannot be correctly rendered. +

+ + + +

+ ... This property specifies the content-type and may be used + by a User Agent to select a rendering + processor for the object. +

+ +

+ No identification of the content-type. The User + Agent may determine it by "sniffing" or by other + means. +

+ + + +

+ ... If an element's border color is not specified with a + "border" property, user agents must use the + value of the element's "color" property as the computed + value for the border color. +

+ + +

+ ... Rows, columns, row groups, and column groups cannot have + borders (i.e., user agents must ignore the + border properties for those elements). +

+ + +

+ ... If no font with the indicated characteristics exists on + a given platform, the user agent should + either intelligently substitute (e.g., a smaller version of + the "caption" font might be used for the "small-caption" + font), or substitute a user agent default + font. +

+ + +

Initial: depends on user agent

+ + +

+ ... Relative page boxes allow user agents + to scale a document and make optimal use of the target size. +

+ ... User agents 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). +

+ Rendering page boxes that do not fit a target sheet
+ If a page box does not fit the target sheet dimensions, + the user agent may choose to: +
- + Rotate the page box 90 degrees if this will make the + page box fit. +
- Scale the page to fit the target.
+ The user agent should consult the user + before performing these operations. +
+ Positioning the page box on the sheet
When the page + box is smaller than the target size, the user + agent is free to place the page box anywhere on + the sheet. +

+ + + +

+ This value directs user agents to + collapse sequences of whitespace, and break lines as + necessary to fill line boxes. ... +

+ + +

+ This value prevents user agents from + collapsing sequences of whitespace. ... +

+ +

+ ... Conforming user agents may ignore the + 'white-space' property in author and user style sheets but + must specify a value for it in the default style sheet. +

+ + + + -- cgit v1.2.3