Home - News ( United States | United Kingdom | Italy | Germany ) - Football scores

Showing content from https://www.w3.org/TR/2017/WD-css-align-3-20170407/ below:

CSS Box Alignment Module Level 3

This section is not normative.

CSS Levels 1 and 2 allowed for the alignment of text via text-align and the alignment of blocks by balancing auto margins. However, except in table cells, vertical alignment was not possible. As CSS adds further capabilities, the ability to align boxes in various dimensions becomes more critical. This module attempts to create a cohesive and common box alignment model to share among all of CSS.

Note: The alignment of text and inline-level content is defined in [CSS-TEXT-3] and [CSS-INLINE-3].

This module adds some new alignment capabilities to the block layout model described in [CSS2] chapters 9 and 10 and defines the interaction of these properties with the alignment of table cell content using vertical-align, as defined in [CSS2] chapter 17.

The interaction of these properties with Grid Layout [CSS-GRID-1] and Flexible Box Layout [CSS-FLEXBOX-1] is defined in their respective modules. The property definitions here supersede those in [CSS-FLEXBOX-1] (which have a smaller, earlier subset of permissible values).

No properties in this module apply to the ::first-line or ::first-letter pseudo-elements.

This specification follows the CSS property definition conventions from [CSS2]. Value types not defined in this specification are defined in CSS Level 2 Revision 1 [CSS2]. Other CSS modules may expand the definitions of these value types: for example [CSS3VAL], when combined with this module, adds the initial keyword as a possible property value.

In addition to the property-specific values listed in their definitions, all properties defined in this specification also accept the inherit keyword as their property value. For readability it has not been repeated explicitly.

The box alignment properties in CSS are a set of 6 properties that control alignment of boxes within other boxes. They can be described along two axises:

• which dimension they apply to (main/inline vs. cross/block), and
• whether they control the position of the box within its parent, or the box’s content within itself.

Note: This specification uses the terms “justify” and “align” to distinguish between alignment in the main/inline and cross/block dimensions, respectively. The choice is somewhat arbitrary, but having the two terms allows for a consistent naming scheme that works across all of CSS’s layout models (including CSS Flexbox 1 §2 Flex Layout Box Model and Terminology)

The following table summarizes the box alignment properties and the display types they can apply to.

Note: The *-items properties don’t affect the element itself. When set on a container, they specify the interpretation of any *-self: auto used on children of the container element.

Since this module defines alignment properties for all layout modes in CSS, some abstract terminology is introduced:

alignment subject

The alignment subject is the thing or things being aligned by the property. For justify-self and align-self, the alignment subject is the margin box of the box the property is set on. For justify-content and align-content, the alignment subject is defined by the layout mode and refers to some aspect of its contents.

alignment container

The alignment container is the rectangle that the alignment subject is aligned within. This is defined by the layout mode, but is usually the alignment subject’s containing block.

fallback alignment

Some alignments can only be fulfilled in certain situations or are limited in how much space they can consume; for example, space-between can only operate when there is more than one alignment subject, and baseline alignment, once fulfilled, might not be enough to absorb all the excess space. In these cases a fallback alignment takes effect (as defined below) to fully consume the excess space.

All of the alignment properties use a common set of keyword values, which are defined in this section. Keywords fall into three categories:

positional alignment

These keywords define alignment as an absolute position within the alignment container.

baseline alignment

These keywords define alignment as a relationship among the baselines of multiple alignment subjects within an .

distributed alignment

These keywords define alignment as a distribution of space among alignment subjects.

The positional alignment keywords specify a position for an alignment subject with respect to its alignment container.

Values have the following meanings:

center (self, content)

Centers the alignment subject within its alignment container.

start (self, content)

Aligns the alignment subject to be flush with the alignment container’s start edge in the appropriate axis.

end (self, content)

Aligns the alignment subject to be flush with the alignment container’s end edge in the appropriate axis.

self-start (self)

Aligns the alignment subject to be flush with the edge of the alignment container corresponding to the alignment subject’s start side in the appropriate axis.

self-end (self)

Aligns the alignment subject to be flush with the edge of the alignment container corresponding to the alignment subject’s end side in the appropriate axis.

flex-start (self, content)

Only used in flex layout. [CSS-FLEXBOX-1] Aligns the alignment subject to be flush with the edge of the alignment container corresponding to the flex container’s main-start or cross-start side, as appropriate. When used on boxes that are not children of a flex container, this value behaves as start.

flex-end (self, content)

Only used in flex layout. Aligns the alignment subject to be flush with the edge of the alignment container corresponding to the flex container’s main-end or cross-end side, as appropriate. When used on boxes that are not children of a flex container, this value behaves as end.

left (self, content)

Aligns the alignment subject to be flush with the alignment container’s line-left edge. If the property’s axis is not parallel with the inline axis, this value behaves as start.

right (self, content)

Aligns the alignment subject to be flush with the alignment container’s line-right edge. If the property’s axis is not parallel with the inline axis, this value behaves as start.

Two grammar terms are used to denote this collection of values:

<self-position>

This set is used by justify-self and align-self to align the box within its alignment container, and also by justify-items and align-items (to specify default values for justify-self and align-self).

<self-position> = center | start | end | self-start | self-end |
        flex-start | flex-end | left | right;

<content-position>

This set is used by justify-content and align-content to align the box’s contents within itself.

<content-position> = center | start | end | flex-start | flex-end | left | right;

Add example images.

Make it easier to understand the dual-axis nature of "start" and "end" wrt orthogonal flows.

See CSS Writing Modes 3 §4.1 Introduction to Baselines.

Baseline alignment is a form of positional alignment that aligns multiple alignment subjects within a (such as cells within a row or column) by matching up their alignment baselines. If an alignment subject’s position is not fully determined by baseline alignment it and the other participants in its baseline-sharing group are fallback-aligned insofar as possible while preserving their baseline alignment.

The baseline alignment keywords are represented with the <baseline-position> grammar term:

<baseline-position> = [ first | last ]? baseline

The first and last values give a box a baseline alignment preference: either “first” or “last”, respectively, defaulting to “first”.

Values have the following meanings:

baseline

Computes to first baseline, defined below.

first baseline

Specifies participation in first-baseline alignment: aligns the alignment baseline of the box’s first baseline set with the corresponding baseline of its . See §8.3 Aligning Boxes by Baseline for more details.

The fallback alignment for first baseline is start.

last baseline

Specifies participation in last-baseline alignment: aligns the alignment baseline of the box’s last baseline set with the corresponding baseline of its . See §8.3 Aligning Boxes by Baseline for more details.

The fallback alignment for last baseline is end.

Should this end fallback be safe or unsafe?

When specified for align-content/justify-content, these values trigger baseline content-alignment, shifting the content of the box within its content box, and may also affect the sizing of the box itself. See §5.2 Baseline Content-Alignment.

When specified for align-self/justify-self, these values trigger baseline self-alignment, shifting the entire box within its container, which may affect the sizing of its container. See §6.4 Baseline Self-Alignment.

If both baseline content-alignment and baseline self-alignment are specified in the same axis on the same box, only baseline self-alignment is honored in that axis; the content-alignment in that axis must be treated as start.

Add example images here.

If a box does not belong to a , then the fallback alignment is used. For example, align-content: baseline on a block box falls back to start alignment. The fallback alignment is also used to align the aligned subtree within its alignment container.

Note: Because they are equivalent, and baseline is shorter, the CSSOM serializes first baseline as baseline.

Note: For the somewhat-related vertical-align property, due to inconsistent design decisions in CSS2.1, baseline is not equivalent to first baseline as an inline-level box’s baseline alignment preference depends on display. (E.g., inline-block uses its last baseline by default, while inline-table uses its first baseline by default.)

The distributed alignment values are used by justify-content and align-content to disperse a container’s extra space among its alignment subjects.

When space cannot be distributed in this way, these values behave as their fallback alignment. Each distribution value has a default fallback alignment, but one can alternatively be specified explicitly in the property.

space-between

The alignment subjects are evenly distributed in the alignment container. The first alignment subject is placed flush with the start edge of the alignment container, the last alignment subject is placed flush with the end edge of the alignment container, and the remaining alignment subjects are distributed so that the spacing between any two adjacent alignment subjects is the same.

The default fallback alignment for this value is start.

space-around

The alignment subjects are evenly distributed in the alignment container, with a half-size space on either end. The alignment subjects are distributed so that the spacing between any two adjacent alignment subjects is the same, and the spacing before the first and after the last alignment subject is half the size of the other spacing.

The default fallback alignment for this value is center.

space-evenly

The alignment subjects are evenly distributed in the alignment container, with a full-size space on either end. The alignment subjects are distributed so that the spacing between any two adjacent alignment subjects, before the first alignment subject, and after the last alignment subject is the same.

The default fallback alignment for this value is center.

stretch

If the combined size of the alignment subjects is less than the size of the alignment container, any auto-sized alignment subjects have their size increased equally (not proportionally), while still respecting the constraints imposed by max-height/max-width (or equivalent functionality), so that the combined size exactly fills the alignment container.

The default fallback alignment for this value is flex-start. (For layout modes other than flex layout, flex-start is identical to start.)

These values are represented with the <content-distribution> grammar term:

<content-distribution> = space-between | space-around | space-evenly | stretch

When the alignment subject is larger than the alignment container, it will overflow. Some alignment modes, if honored in this situation, may cause data loss: for example, if the contents of a sidebar are centered, when they overflow they may send part of their boxes past the viewport’s start edge, which can’t be scrolled to.

To help combat this problem, an overflow alignment mode can be explicitly specified. “Unsafe” alignment honors the specified alignment mode in overflow situations, even if it causes data loss, while “safe” alignment changes the alignment mode in overflow situations in an attempt to avoid data loss.

<overflow-position> = unsafe | safe

safe

If the size of the alignment subject overflows the alignment container, the alignment subject is instead aligned as if the alignment mode were start.

unsafe

Regardless of the relative sizes of the alignment subject and alignment container, the given alignment value is honored.

If the overflow alignment isn’t explicitly specified, the default overflow alignment is similar to unsafe in that an overflowing alignment subject is allowed to overflow its alignment container; however if this would cause it to also overflow the scrollable overflow region of its nearest ancestor scroll container, then its overflow in that direction is limited by biasing any remaining overflow to the end side. In other words, it is similar to safe alignment except that the limit for switching to start is triggered by overflowing the scrollable area, rather than merely overflowing the alignment container.

The figure below illustrates the difference in "safe" versus "unsafe" centering, using a column flexbox as an example:

About

Authoritarianism

Blog

About

Authoritarianism

Blog

It may not be Web-compatible to implement the “smart” default behavior (though we hope so, and believe it to be likely), so UAs should pass any feedback on this point to the WG. UAs that have not implemented the “smart” default behavior must behave as unsafe.

The content distribution properties align-content and justify-content (and their place-content shorthand) control alignment of the box’s content within its content box.

Aligns the contents of the box as a whole. Values other than normal are defined in §4 Alignment Keywords, above. If both a <content-distribution> and <content-position> are given, the <content-position> provides an explicit fallback alignment.

This shorthand property sets both the align-content and justify-content properties in one declaration. The first value is assigned to align-content. The second value is assigned to justify-content; if omitted, it is copied from the first value.

See [CSS-FLEXBOX-1] for details.

See [CSS-GRID-1] for details.

The content of boxes participating in row-like layout contexts () can be baseline-aligned to each other. This effectively increases the padding on the box to align the alignment baseline of its contents with that of other baseline-aligned boxes in its baseline-sharing group.

The set of boxes that participate in baseline content-alignment depends on the layout model:

Table Cells:

A table cell participates in first (last) baseline content-alignment in either its row or column (whichever matches its inline axis) if its computed align-content is first baseline (last baseline).

Flex Items:

A flex item participates in first (last) baseline content-alignment in its flex line if its computed align-content is first baseline (last baseline), its inline axis is parallel to the main axis, and its computed align-self is stretch or self-start (self-end). For this purpose, the start, end, flex-start, and flex-end values of align-self are treated as either self-start or self-end, whichever they end up equivalent to.

Grid Items:

A grid item participates in first (last) baseline content-alignment in either its row or column (whichever matches its inline axis) if its computed align-content is first baseline (last baseline), and its computed align-self or justify-self (whichever affects its block axis) is stretch or self-start (self-end). For this purpose, the start, end, flex-start, and flex-end values of align-self are treated as either self-start or self-end, whichever they end up equivalent to.

If a box spans multiple , it participates in first (last) baseline content-alignment within its start-most (end-most) along that axis.

When a box participates in first (last) baseline content-alignment it effectively aligns its start (end) edge with the other boxes in its baseline-sharing group, then gains additional start (end) padding to align its alignment subject’s (i.e. content’s) baseline with those of its baseline-sharing group. See §8.3 Aligning Boxes by Baseline for exact details. This can increase the intrinsic size of the box.

The content distribution properties also affect the initial scroll position, setting it to display the appropriate portion of the scrollable area. In other words, the scrollable overflow region is aligned relative to the viewport as specified by the content distribution properties. Additionally, so that the content remains in the scrollable overflow region in order to be scrollable, the scroll and auto values of overflow trigger safe content alignment always.

The align-self and justify-self properties (and their place-self shorthand) control alignment of the box within its containing block.

Justifies the box (as the alignment subject) within its containing block (as the alignment container) along the inline/row/main axis: the box’s outer edges are aligned within its alignment container as described by its alignment value. Values have the following meanings:

auto

Behaves as normal if the box has no parent, or when determining the actual position of an absolutely positioned box. It behaves as the computed justify-items value of the parent box (minus any legacy keywords) otherwise (including when determining the static position of an absolutely positioned box).

normal

Represents the “default” alignment for the layout mode. Its behavior depends on the layout mode, as described below.

stretch

When the box’s computed width/height (as appropriate to the axis) is auto and neither of its margins (in the appropriate axis) are auto, sets the box’s used size to the length necessary to make its outer size as close to filling the alignment container as possible while still respecting the constraints imposed by min-height/min-width/max-height/max-width. Unless otherwise specified, this value falls back to flex-start.

Should stretch allow a fallback alignment, like it does on align-content and justify-content?

Note: The stretch keyword can cause elements to shrink, to fit their container.

<baseline-position>

Indicates baseline content-alignment, as defined in §4.2 Baseline Alignment: the baseline keyword and first/last modifiers, §6.4 Baseline Self-Alignment, and §8 Baseline Alignment Details.

<overflow-position>? && <self-position>

Defined in §4 Alignment Keywords, above.

Values other than stretch cause a width/height of auto to be treated as fit-content.

Note: auto margins, because they effectively adjust the size of the margin area, take precedence over justify-self.

This is the legacy behavior of HTML align. Do we want to still do this, or should we do the centering behavior of margins, which center while ignoring floats, then shift if necessary to avoid overlapping?

This property does not apply to floats.

The effect of these rules is that an auto-sized block-level table, for example, can be aligned while still having side margins. If the table’s max-content size is narrower than its containing block, then it is shrink-wrapped to that size and aligned as specified. If the table’s max-content size is wider, then it fills its containing block, and the margins provide appropriate spacing from the containing block edges.

If neither offset in thix axis is auto, but width (height, for vertical writing modes) is auto, the width (height) is treated as stretch and auto margins are treated as zero. (Otherwise, when justify-self is not normal, width: auto (height: auto) is treated as fit-content and auto margins are used for alignment as in in-flow block-level layout.)

Values other than stretch cause non-replaced absolutely-positioned boxes to use fit-content sizing for calculating auto inline sizes.

Note that stretch does cause replaced absolutely-positioned boxes to fill their containing block just as non-replaced ones do.

If either offset property in this dimension is auto, justify-self has no effect.

This property does not apply to table cells, because their position and size is fully constrained by table layout.

This property does not apply to flex items, because there is more than one item in the main axis. See flex for stretching and justify-content for main-axis alignment. [CSS-FLEXBOX-1]

See [CSS-GRID-1] for details.

Aligns the box within its containing block along the block/column/cross axis: the box’s outer edges are aligned within its alignment container as described by its alignment value. Values have the following meanings:

auto

Behaves as normal if the box has no parent, or when determining the actual position of an absolutely positioned box. It behaves as the computed align-items value of the parent box (minus any legacy keywords) otherwise (including when determining the static position of an absolutely positioned box).

normal

Represents the “default” alignment for the layout mode, as defined below.

stretch

As defined for justify-self in §6.1 Inline/Main-Axis Alignment: the justify-self property.

<baseline-position>

Indicates baseline content-alignment, as defined in §4.2 Baseline Alignment: the baseline keyword and first/last modifiers, §6.4 Baseline Self-Alignment, and §8 Baseline Alignment Details.

<overflow-position>? && <self-position>

Defined in §4 Alignment Keywords, above.

Note: auto margins, because they effectively adjust the size of the margin area, take precedence over align-self.

The align-self property does not apply to block-level boxes (including floats), because there is more than one item in the block axis.

If neither offset in thix axis is auto, but height (width, for vertical writing modes) is auto, the height (width) is treated as stretch and auto margins are treated as zero. (Otherwise, when align-self is not normal, height: auto (width: auto) is treated as fit-content and auto margins are used for alignment as in in-flow block-level layout.)

Values other than stretch cause non-replaced absolutely-positioned boxes to use shrink-to-fit sizing for calculating auto block sizes.

Note that stretch does cause replaced absolutely-positioned boxes to fill their containing block just as non-replaced ones do.

If either offset property in this dimension is auto, align-self has no effect.

This property does not apply to table cells, because their position and size is fully constrained by table layout.

See [CSS-FLEXBOX-1] for details.

This shorthand property sets both the align-self and justify-self properties in a single declaration. The first value is assigned to align-self. The second value is assigned to justify-self; if omitted, it is copied from the first value.

Boxes participating in row-like layout contexts () can be baseline-aligned to each other. This effectively increases the margins on the box to align its alignment baseline with that of other baseline-aligned boxes in its baseline-sharing group.

The set of boxes that participate in baseline self-alignment depends on the layout model:

Flex Items:

A flex item participates in first (last) baseline self-alignment in its flex line if its computed align-self is first baseline (last baseline). See [CSS-FLEXBOX-1] for details.

Grid Items:

A grid item participates in first (last) baseline self-alignment in its row or column if its align-self or justify-self property (respectively) computes to first baseline (last baseline).

If a box spans multiple , it participates in first (last) baseline self-alignment within its start-most (end-most) along that axis.

When a box participates in first (last) baseline self-alignment it effectively first aligns its start (end) edge with the other boxes in its baseline-sharing group, then gains additional start (end) margin to align its baseline with those of its baseline-sharing group. See §8.3 Aligning Boxes by Baseline for exact details. This can increase the intrinsic size of the box.

The align-items and justify-items properties (and their place-items shorthand) set the default align-self and justify-self behavior of the element’s child boxes.

This property specifies the default justify-self for all of the child boxes (including anonymous boxes) participating in this box’s formatting context. Values have the following meanings:

auto

If the inherited value of justify-items includes the legacy keyword, auto computes to the inherited value.

Otherwise, auto computes to normal.

legacy

This keyword causes the value to effectively inherit into descendants. It can only be combined with the center, left, and right positions. When justify-self:auto retrieves the value of justify-items, only the alignment keyword, not the legacy keyword, is passed to it. It exists to implement the legacy alignment behavior of HTML’s <center> element and align attribute.

Other values have no special handling and are merely passed to justify-self.

The auto keyword exists solely to implement the legacy inheritance property. We could just rename it to legacy, since it computes away to normal unless you’re using legacy anyway.

The legacy keyword acts weird, to make it behave like an inherited value even though this property is not inherited. We don’t mix inheritance and non-inheritance anywhere else, because it’s a bad code smell. Should we remove legacy and make a separate inheriting property for it? Or just drop the behavior entirely and let it remain special HTML magic?

This property specifies the default align-self for all of the child boxes (including anonymous boxes) participating in this box’s formatting context.

Values have no special handling and are merely passed to align-self.

This shorthand property sets both the align-items and justify-items properties in a single declaration. The first value is assigned to align-items. The second value is assigned to justify-items; if omitted, it is copied from the first value.

Boxes in a baseline-sharing group are aligned to each other using their alignment baselines. For example, in horizontal writing modes, specifying align-content: baseline on table cells in the same row will align the baselines of their first formatted lines. This section defines exactly how baseline alignment is performed in consideration of the myriad baselines and writing modes that exist in internationalized modern CSS.

A baseline set is a set of baselines (alphabetic, central, etc.) associated with a common baseline table. Typically, a typesetting tradition will use only one of these, but different writing systems use different baselines, and mixing writing systems can result in using more than one within a single line. Refer to CSS Writing Modes 3 §4.1 Introduction to Baselines for more information on baselines and writing modes.

The first baseline set (and last baseline set) of a box for a given axis is the baseline set nominally associated with the first (last) line of text within the box. The alignment baseline is one of these, usually the dominant baseline associated with the . (See the dominant-baseline and alignment-baseline properties in [CSS-INLINE-3].)

The first and last baseline sets of a box are determined differently based on the layout model, as follows:

block containers

The first (last) baseline set of a block container is generated from the dominant first (last) baseline of the first (last) in-flow line box in the block container, or is taken from the first (last) in-flow block-level child in the block container that contributes a set of first (last) baselines, whichever comes first (last). If there is no such line box or child, then the block container has no baseline set.

tables

The first (last) baseline set of a table box is the first (last) baseline set of its first (last) row.

When finding the first (last) baseline set of an inline-block, any baselines contributed by table boxes must be skipped. (This quirk is a legacy behavior from [CSS2].)

table rows

If any cells in the row participate in first baseline (last baseline) alignment along the row axis, the first (last) baseline set of the row is generated from their shared alignment baseline and the row’s first available font, after alignment has been performed. Otherwise, the first (last) baseline set of the row is synthesized from the lowest and highest content edges of the cells in the row. [CSS2]

flex containers

See Flex Baselines in [CSS-FLEXBOX-1].

grid containers

See Grid Baselines in [CSS-GRID-1].

To generate baselines for a box from a single baseline, use the baseline table from the font settings and first available font of that box, and align that baseline set to the given single baseline.

To synthesize baselines from a rectangle (or two parallel lines), synthesize the alphabetic baseline from the lower line, and the central baseline by averaging the positions of the two edges or lines. See CSS Inline Layout 3 § Synthesizing Baselines for rules on synthesizing additional baselines.

Note: The edges used to synthesize baselines from a box depend on their formatting context: inline-level boxes synthesize from their margin edges [CSS-INLINE-3], table cells synthesize from their content edges [CSS2], and grid and flex items synthesize from their border edges [CSS-GRID-1] [CSS-FLEXBOX-1].

Maybe these things are wrong? CSS 2.1 is really weird about baseline alignment.

For the purposes of finding the baselines of a box, it and all its in-flow descendants with a scrolling mechanism (see the overflow property) must be considered as if scrolled to their origin. Furthermore, if, in the case of a box with non-visible overflow, the resulting position of a first (last) baseline is past a box’s end (start) margin edge, its position is clamped to that margin edge.

This reflects the latest CSS2.1 errata, however see also discussion of an alternate solution that was previously drafted here.

A baseline-sharing group is composed of boxes that participate in baseline alignment together. This is possible only if they

• Share an along an axis perpendicular to their baseline alignment axis.
• Have compatible baseline alignment preferences (i.e., the baselines that want to align are on the same side of the alignment context).

Boxes share an , along a particular axis, and established by a particular box, .when they are:

• table cells in the same row, along the table’s row (inline) axis, established by the row box
• table cells in the same column, along the table’s column (block) axis, established by the column box
• grid items in the same row, along the grid’s row (inline) axis, established by the grid container
• grid items in the same column, along the grid’s colum (block) axis, established by the grid container
• flex items in the same flex line, along the flex container’s main axis, established by the flex container

Note: Conceptually, the inline-level boxes in a line box also share a self-alignment context and participate in a baseline-sharing group; however they only baseline-align in response to the vertical-align property, not any of the properties defined in this module. See [CSS-INLINE-3].

The baseline alignment preferences of two boxes in a baseline-sharing group are compatible if they have:

• the same block flow direction and baseline alignment preference

• opposite block flow direction and opposite baseline alignment preference

For this purpose, boxes whose block flow direction is parallel to the ’s axis are treated as having a block flow direction orthogonal to the axis and directed end-ward relative to the box that establishes the , and their baselines are synthesized accordingly.

Given a set of alignment subjects and their baselines that all belong to a single baseline-sharing group, the alignment subjects are baseline-aligned as follows:

First, generate the baseline table from its first available font and overlay also the mirror of this baseline table by aligning their central baselines. These are the baseline “grids” to which the alignment subjects will align.

Next, align each alignment subject by its specified alignment baseline to the baseline table or its mirror, whichever matches the alignment subject’s line orientation. Unless otherwise specified (e.g. via the alignment-baseline property), the alignment baseline is the dominant baseline of the .

Position this aligned subtree within the alignment container according to the fallback alignment associated with the specified baseline alignment preference. For first (last) baseline content-alignment, then add the minimum necessary extra space between the alignment container’s start (end) content edge and the alignment subject’s edge to align the start (end) margin edges of all the alignment containers in the while maintaining baseline alignment within the aligned subtee.

Changes since the previous Working Draft are a handful of clarifications.

As a simple layout spec, this introduces no new privacy or security considerations.

Special thanks goes to Javier Fernandez, Markus Mielke, Alex Mogilevsky, and the participants in the CSSWG’s March 2008 F2F alignment discussions.

Conformance requirements are expressed with a combination of descriptive assertions and RFC 2119 terminology. The key words “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “MAY”, and “OPTIONAL” in the normative parts of this document are to be interpreted as described in RFC 2119. However, for readability, these words do not appear in all uppercase letters in this specification.

All of the text of this specification is normative except sections explicitly marked as non-normative, examples, and notes. [RFC2119]

Examples in this specification are introduced with the words “for example” or are set apart from the normative text with class="example", like this:

Informative notes begin with the word “Note” and are set apart from the normative text with class="note", like this:

Note, this is an informative note.

Advisements are normative sections styled to evoke special attention and are set apart from other normative text with <strong class="advisement">, like this: UAs MUST provide an accessible alternative.

A style sheet is conformant to this specification if all of its statements that use syntax defined in this module are valid according to the generic CSS grammar and the individual grammars of each feature defined in this module.

A renderer is conformant to this specification if, in addition to interpreting the style sheet as defined by the appropriate specifications, it supports all the features defined by this specification by parsing them correctly and rendering the document accordingly. However, the inability of a UA to correctly render a document due to limitations of the device does not make the UA non-conformant. (For example, a UA is not required to render color on a monochrome monitor.)

An authoring tool is conformant to this specification if it writes style sheets that are syntactically correct according to the generic CSS grammar and the individual grammars of each feature in this module, and meet all other conformance requirements of style sheets as described in this module.

The following sections define several conformance requirements for implementing CSS responsibly, in a way that promotes interoperability in the present and future.

So that authors can exploit the forward-compatible parsing rules to assign fallback values, CSS renderers must treat as invalid (and ignore as appropriate) any at-rules, properties, property values, keywords, and other syntactic constructs for which they have no usable level of support. In particular, user agents must not selectively ignore unsupported property values and honor supported values in a single multi-value property declaration: if any value is considered invalid (as unsupported values must be), CSS requires that the entire declaration be ignored.

Once a specification reaches the Candidate Recommendation stage, implementers should release an unprefixed implementation of any CR-level feature they can demonstrate to be correctly implemented according to spec, and should avoid exposing a prefixed variant of that feature.

To establish and maintain the interoperability of CSS across implementations, the CSS Working Group requests that non-experimental CSS renderers submit an implementation report (and, if necessary, the testcases used for that implementation report) to the W3C before releasing an unprefixed implementation of any CSS features. Testcases submitted to W3C are subject to review and correction by the CSS Working Group.

RetroSearch is an open source project built by @garambo | Open a GitHub Issue

Search and Browse the WWW like it's 1997 | Search results from DuckDuckGo

HTML: 3.2 | Encoding: UTF-8 | Version: 0.7.3