# CSS Gap Decorations

Editor’s Draft, 18 December 2021

Specification Metadata

This version:
  https://matspalmgren.github.io/css-gap-decorations/Overview.html
Issue Tracking:
  CSSWG Issues Repository
  CSSWG github issue #6748
  Inline In Spec
Editor:
  Mats Palmgren (Mozilla Corporation)
Suggest an Edit for this Spec:
  GitHub Editor

Copyright © 2021 W3C® (MIT, ERCIM, Keio, Beihang). W3C liability, trademark and permissive document license rules apply.

## Abstract

This is a proposal to extend CSS Box Alignment to support gap decorations.

CSS is a language for describing the rendering of structured documents (such as HTML and XML) on screen, on paper, etc.

## Status of this document

This is a public copy of the editors’ draft. It is provided for discussion only and may change at any moment. Its publication here does not imply endorsement of its contents by W3C. Don’t cite this document other than as work in progress.

Please send feedback by filing issues in GitHub (preferred), including the spec code “css-gap-decorations” in the title, like this: “[css-gap-decorations] …summary of comment…”. All issues and comments are archived. Alternately, feedback can be sent to the (archived) public mailing list www-style@w3.org.

This document is governed by the 2 November 2021 W3C Process Document.

## 1. Introduction

This section is not normative.

### 1.1. Overview

This is a proposal to add CSS features for decorating gaps. (Some use cases and background discussion can be found in issue #2748.) We propose to extend the column-rule-width property with new values. Add properties to support images and gradients. Add properties for aligning the rule to specific anchor points, specifying its extent area, and to control its position and length within that area. We add support for row rules by adding the corresponding row-* properties. We also widen the scope of these properties so that they can be used in flex containers, grid containers, table and table-row-group containers, as well as multi-column containers.

### 1.2. Module Interactions

This module extends the definition of the column-rule-width property, adding <percentage> and auto values. We also generalize the existing column-rule-* properties to apply to other types of containers. Accordingly, we propose to move the existing column-rule properties from the Multi-column spec to the Box Alignment spec. Additionally, all new properties and shorthands in this proposal are intended as additions to the Box Alignment spec.

### 1.3. Definitions

In this specification, we will use the term lateral axis to refer to the axis in which the rule’s thickness grows (i.e. the axis column-rule-width use). The other axis is the rule’s longitudinal axis and its size in this axis is the rule length. These definitions are relative to the rule itself and does not depend on if the rule is a row or column rule, or what the writing-mode is.

## 2. Rule Images and Gradients

Authors may specify an image or gradient to be used in place of the column-rule-style. These properties are loosely modeled after the corresponding border-image-* properties. Rules are one-dimensional though, as opposed to borders which have four sides around an area. A rule is like a border with just one side rendered with the other sides having border-style: none.

### 2.1. The column-rule-image-source and row-rule-image-source Properties

Name: | column-rule-image-source, row-rule-image-source
Value: | none | <image>
Initial: | none
Applies to: | multi-column containers, flex containers, grid containers, table and table-row-group containers
Inherited: | no
Percentages: | N/A
Computed value: | the keyword none or the computed <image>
Canonical order: | per grammar
Animation type: | discrete

These properties specify an <image> to use in place of the rendering specified by the column-rule-style/row-rule-style properties.

As for borders, a rule image is not rendered when the corresponding column-rule-style/row-rule-style is none.

### 2.2. The column-rule-image-slice and row-rule-image-slice Properties

Name: | column-rule-image-slice, row-rule-image-slice
Value: | [<number [0,∞]> | <percentage [0,∞]>]{1,2}
Initial: | 0
Applies to: | multi-column containers, flex containers, grid containers, table and table-row-group containers
Inherited: | no
Percentages: | refer to image size in the rule’s longitudinal axis
Computed value: | one or two values, each either a number or percentage
Canonical order: | per grammar
Animation type: | discrete

column-rule-image-slice specify inward offsets from the start and end edges of the image in the rule’s longitudinal axis, dividing it into three regions: two edge areas and one middle area.

When two values are specified, they set the offsets on the start and end sides in that order. If the end value is missing, it is the same as the start value.

<percentage [0,∞]>
  Percentages are relative to the image size in the rule’s longitudinal axis
<number [0,∞]>
  Numbers represent pixels in the image (if the image is a raster image) or vector coordinates (if the image is a vector image).

Negative values are not allowed. Computed values larger than the size of the image are interpreted as 100%.

If the image must be sized to determine the slices (for example, for SVG images with no intrinsic size), then it is sized using the CSS Images 3 § 4.3.1 Default Sizing Algorithm with no specified size and the rule containing rectangle as the default object size.

The regions given by the column-rule-image-slice values may overlap. However if the sum of the start and end values is equal to or greater than the size of the image, the middle part becomes empty.

### 2.3. The column-rule-image-repeat and row-rule-image-repeat Properties

Name: | column-rule-image-repeat, row-rule-image-repeat
Value: | stretch | repeat | round | space
Initial: | stretch
Applies to: | multi-column containers, flex containers, grid containers, table and table-row-group containers
Inherited: | no
Percentages: | N/A
Computed value: | the specified keyword
Canonical order: | per grammar
Animation type: | discrete

These properties specify how the middle part of a sliced rule image is scaled and tiled. Values have the following meanings:

stretch
  The image is stretched to fill the area.
repeat
  The image is tiled (repeated) to fill the area.
round
  The image is tiled (repeated) to fill the area. If it does not fill the area with a whole number of tiles, the image is rescaled so that it does.
space
  The image is tiled (repeated) to fill the area. If it does not fill the area with a whole number of tiles, the extra space is distributed around the tiles.

The exact process for scaling and tiling the image parts is defined by drawing the equivalent border-image with the top and bottom border-image-slice values set from the corresponding column-rule-image-slice values, and the border-image-slice left value set to 100% and the right value set to 0. The border-image-width top value set to the column-rule-image-slice top value. The border-image-width top value set to the column-rule-image-slice bottom value. The border-image-width top value set to zero.

### 2.4. The column-rule-image and row-rule-image Shorthands

Name: | column-rule-image, row-rule-image
Value: | <'column-rule-image-source'> || <'column-rule-image-slice'> || <'column-rule-image-repeat'>
Initial: | see individual properties
Applies to: | multi-column containers, flex containers, grid containers, table and table-row-group containers
Inherited: | see individual properties
Percentages: | see individual properties
Computed value: | see individual properties
Animation type: | see individual properties
Canonical order: | per grammar

This example demonstrates the new rule image properties presented above in a grid layout with spanning elements.
Example of image rules.
Here’s a variation of the example above that animates the container’s size and stretch the middle part of the images.
Example of stretching image rules when the container is resized.
This is a similar example using gradients.
Example of gradient rules.
Here’s an example demonstrating support for a use case mentioned in issue #2748. It’s a coupon with a perforation rendered by a semi-transparent rule image between two flex items.
An example of a semi-transparent column rule image.

## 3. Rule Positioning and Sizing

### 3.1. The column-rule-width and row-rule-width Properties

Name: | column-rule-width
New values: | <percentage> | auto
Initial: | medium
Applies to: | multi-column containers, flex containers, grid containers, table and table-row-group containers
Inherited: | no
Percentages: | refer to the rule containing rectangle’s size in the rule’s lateral axis
Computed value: | absolute length if the specified value is <line-width>; 0px if the column rule style is none or hidden. Otherwise, the specified value.
Animation type: | by computed value type

Name: | row-rule-width
Value: | <line-width> | <percentage> | auto
Initial: | medium
Applies to: | multi-column containers, flex containers, grid containers, table and table-row-group containers
Inherited: | no
Percentages: | refer to the rule containing rectangle’s size in the rule’s lateral axis
Computed value: | absolute length if the specified value is <line-width>; 0px if the column rule style is none or hidden. Otherwise, the specified value.
Canonical order: | per grammar
Animation type: | by computed value type

These properties sets the thickness (lateral size) of a rule in the column and row axis, respectively. Negative specified values are not allowed. The used value is floored at zero (in case a 'calc()' expression evaluates to a negative value for example).

See § 3.4 Resolving a rule’s position and size below for how auto is resolved.

### 3.2. The column-rule-length and row-rule-length Properties

Name: | column-rule-length, row-rule-length
Value: | <length-percentage> | auto
Initial: | auto
Applies to: | multi-column containers, flex containers, grid containers, table and table-row-group containers
Inherited: | no
Percentages: | refer to the rule containing rectangle’s size in the rule’s longitudinal axis
Computed value: | the specified value
Canonical order: | per grammar
Animation type: | by computed value type

These properties sets the rule length (longitudinal size) of a rule in the column and row axis, respectively. Negative specified values are not allowed. The used value is floored at zero (in case a 'calc()' expression evaluates to a negative value for example).

See § 3.4 Resolving a rule’s position and size below for how auto is resolved.

Note: These properties work the same as the *-rule-width properties in the lateral axis, except that they have a different initial value.

### 3.3. The Rule Lateral Inset Properties

Name: | column-rule-lateral-inset-start, column-rule-lateral-inset-end, row-rule-lateral-inset-start, row-rule-lateral-inset-end
Value: | <length-percentage> | auto
Initial: | auto
Applies to: | multi-column containers, flex containers, grid containers, table and table-row-group containers
Inherited: | no
Percentages: | refer to the rule containing rectangle’s size in the rule’s lateral axis
Computed value: | the specified value
Canonical order: | per grammar
Animation type: | by computed value type

These properties sets the lateral start/end offset of the rule in the column and row axis, respectively. A positive value moves the position inward and a negative value outward from the corresponding rule containing rectangle’s edge.

This example demonstrates aligning a rule at the start of the gap.
Examples of aligning a rule at the start of the gap with a lateral start offset.
This example demonstrates aligning a rule at the end of the gap.
Examples of aligning a rule at the end of the gap with a lateral end offset.

NOTE: The column-rule-lateral-inset and column-rule-width used values are calculated in a similar way to how left/right and width are calculated for an absolutely positioned box. The precise algorithm is described next.

### 3.4. Resolving a rule’s position and size

Given a triplet of values: inset-start/end and a size for an axis, auto values are resolved so that the sum of the three values equals the rule containing rectangle size in the same axis. These are the rules for resolving them:

1. if all the values are auto then set both inset values to zero and solve for size
2. if none of the values are auto then the situation is over-constrained: solve by treating the end inset value as auto
3. if both inset properties are auto, but the size is not, then solve with the additional constraint that the inset values must have equal values (resulting in the rule being centered)
4. if the size is auto and only one of the inset values is auto then set the auto inset value to zero and solve for size, if that makes size negative then set the size to zero and solve for the auto inset value instead (i.e. the rule is sized to fill the remaining space, until it becomes zero in which case its positioned at the non-auto inset edge)
5. if the size is auto and both inset values are non-auto then solve for size, if that makes the size negative then set the size to zero and solve again by treating the end inset value as auto

These rules resolves the column-rule-width, column-rule-lateral-inset-start, and column-rule-lateral-inset-end triplet of values in a rule’s lateral axis.

The same rules are also used to resolve column-rule-length, column-rule-longitudinal-[edge-]inset-start, and column-rule-longitudinal-[edge-]inset-end triplet of values in a rule’s longitudinal axis (see the longitudinal property descriptions below for which of the "edge" or non-"edge" values is used).

Ditto for the corresponding row-rule-* properties.

This example demonstrates the rules above. Note in particular the latter two grids, which shows what happens when the sum of the insets are greater than the rule containing rectangle’s size. There’s still a zero-sized column rule there, which the row rule (purple) aligns to.
Examples of lateral rule sizing with various inset values.

### 3.5. The column-rule-lateral-inset and row-rule-lateral-inset Shorthands

Name: | column-rule-lateral-inset
Value: | <'column-rule-lateral-inset-start'> <'column-rule-lateral-inset-end'>?
Initial: | see individual properties
Applies to: | see individual properties
Inherited: | see individual properties
Percentages: | see individual properties
Computed value: | see individual properties
Animation type: | see individual properties
Canonical order: | per grammar

Name: | row-rule-lateral-inset
Value: | <'row-rule-lateral-inset-start'> <'row-rule-lateral-inset-end'>?
Initial: | see individual properties
Applies to: | see individual properties
Inherited: | see individual properties
Percentages: | see individual properties
Computed value: | see individual properties
Animation type: | see individual properties
Canonical order: | per grammar

These are shortands for specifying the corresponding start/end values. If one value is specified it is used for both start and end.

### 3.6. The Rule Longitudinal Inset Properties

Name: | column-rule-longitudinal-inset-start, column-rule-longitudinal-inset-end, row-rule-longitudinal-inset-start, row-rule-longitudinal-inset-end
Value: | <length-percentage> | auto
Initial: | 0
Applies to: | multi-column containers, flex containers, grid containers, table and table-row-group containers
Inherited: | no
Percentages: | refer to the rule containing rectangle’s size in the rule’s longitudinal axis
Computed value: | the specified value
Canonical order: | per grammar
Animation type: | by computed value type

These properties sets the longitudinal start/end inset of the rule in the column and row axis, respectively. They are only used on a rule’s edges that are interior. The *-rule-longitudinal-edge-inset properties are used for rule edges that are on the outer edges of an axis. The used values are calculated the same as for the lateral properties above.

This example shows the default rule alignment and size in both axes.
Example of a rule with default rule alignment and size in both axes.

Note: These have a different initial value than the lateral inset properties, meaning the rule will stretch to fill the rule containing rectangle in this axis. The initial values as specified above are backward compatible with how column rules are sized and positioned in legacy multi-column layout.

Here’s a few simple examples of the rule sizing and inset properties. Note that the grid items have opacity: 0.5 to show any rules underneath them.
Examples of rule sizing and inset values.
This example demonstrates that the inset properties can be animated and that they are relative the rule containing rectangle, which itself depends on the rule’s alignment in its longitudinal axis. Note that the longitudinal insets in this example are definite and not animated. The reason they follow the animated lateral position of the rule in the orthogonal axis is that they have rule alignment.
Example of rule alignment and animated inset values.

### 3.7. The column-rule-longitudinal-inset and row-rule-longitudinal-inset Shorthands

Name: | column-rule-longitudinal-inset
Value: | <'column-rule-longitudinal-inset-start'> <'column-rule-longitudinal-inset-end'>?
Initial: | see individual properties
Applies to: | see individual properties
Inherited: | see individual properties
Percentages: | see individual properties
Computed value: | see individual properties
Animation type: | see individual properties
Canonical order: | per grammar

Name: | row-rule-longitudinal-inset
Value: | <'row-rule-longitudinal-inset-start'> <'row-rule-longitudinal-inset-end'>?
Initial: | see individual properties
Applies to: | see individual properties
Inherited: | see individual properties
Percentages: | see individual properties
Computed value: | see individual properties
Animation type: | see individual properties
Canonical order: | per grammar

These shortands specify the corresponding start/end values. If one value is specified it is used for both start/end.

### 3.8. The Rule Longitudinal Edge Inset Properties

Name: | column-rule-longitudinal-edge-inset-start, column-rule-longitudinal-edge-inset-end, row-rule-longitudinal-edge-inset-start, row-rule-longitudinal-edge-inset-end
Value: | <length-percentage> | auto
Initial: | 0
Applies to: | multi-column containers, flex containers, grid containers, table and table-row-group containers
Inherited: | no
Percentages: | refer to the rule containing rectangle’s size in the rule’s longitudinal axis
Computed value: | the specified value
Canonical order: | per grammar
Animation type: | by computed value type

These properties are identical to their non-"edge" counter-parts. These properties are used on the start edge of the first rule that on the container’s start edge in its longitudinal axis, and the end edge of the last rule at the end of the container. For interior rule edges, the non-"edge" properties are used. In other words, these properties are used together with the *-rule-edge-align properties (defined below) and the *-rule-longitudinal-inset properties are used together with *-rule-align.

### 3.9. The column-rule-longitudinal-edge-inset and row-rule-longitudinal-edge-inset Shorthands

Name: | column-rule-longitudinal-edge-inset
Value: | <'column-rule-longitudinal-edge-inset-start'> <'column-rule-longitudinal-edge-inset-end'>?
Initial: | see individual properties
Applies to: | see individual properties
Inherited: | see individual properties
Percentages: | see individual properties
Computed value: | see individual properties
Animation type: | see individual properties
Canonical order: | per grammar

Name: | row-rule-longitudinal-edge-inset
Value: | <'row-rule-longitudinal-edge-inset-start'> <'row-rule-longitudinal-edge-inset-end'>?
Initial: | see individual properties
Applies to: | see individual properties
Inherited: | see individual properties
Percentages: | see individual properties
Computed value: | see individual properties
Animation type: | see individual properties
Canonical order: | per grammar

These shortands specify the corresponding start/end values. If one value is specified it is used for both start/end.

## 4. Row Rule Style and Color

### 4.1. The row-rule-style and row-rule-color Properties

Name: | row-rule-style
Value: | <line-style>
Initial: | none
Applies to: | multi-column containers, flex containers, grid containers, table and table-row-group containers
Inherited: | no
Percentages: | N/A
Computed value: | specified keyword
Canonical order: | per grammar
Animation type: | discrete

Name: | row-rule-color
Value: | <color>
Initial: | currentcolor
Applies to: | multi-column containers, flex containers, grid containers, table and table-row-group containers
Inherited: | no
Percentages: | N/A
Computed value: | computed color
Canonical order: | per grammar
Animation type: | by computed value type

These properties are the same as the column- properties but for the row rules.

### 4.2. The row-rule Shorthand

This shorthand works the same as column-rule.

Name: | row-rule
Value: | <'row-rule-width'> || <'row-rule-style'> || <'row-rule-color'>
Initial: | see individual properties
Applies to: | see individual properties
Inherited: | see individual properties
Percentages: | see individual properties
Computed value: | see individual properties
Animation type: | see individual properties
Canonical order: | per grammar

lots of new possible shorthands... we now have many properties (and shorthands) with a column-rule and row-rule prefix. Should we add shorthands for some of those with a rule prefix to specify both axes, like so: 'rule-foo: <row-rule-foo> <column-rule-foo>?'. As usual, we have to be careful with the separator though, to make it forward-compatible with any changes we might want to make...

## 5. Rule Alignment

### 5.1. The column-rule-align and row-rule-align Properties

Name: | column-rule-align, row-rule-align
Value: | [gap | gap-center | gap-over | rule | rule-center | rule-over]{1,2}
Initial: | gap
Applies to: | multi-column containers, flex containers, grid containers, table and table-row-group containers
Inherited: | no
Percentages: | N/A
Computed value: | the specified value
Canonical order: | per grammar
Animation type: | discrete

These properties specify the start/end attachment point of the rule containing rectangle in the longitudinal axis. The start value is specified first, the end value second. If only one value is specified it is used for both start and end. These properties are only used for interior edges. The *-rule-edge-align properties described below specify the alignment on the outer edges. The initial value, gap, means that, by default, a rule will stretch its longitudinal size to fill the space from the end of the gap "above" to the start of the gap "below" ("above" meaning the gap in the orthogonal axis on the rule’s start side).

This example illustrates a few alignment options. Note that the row rules all have a 1px longitudinal inset to separate the individual rule segments. (rule-center, for example, would otherwise look like one long rule)

Note also that the column rule is intentionally not centered in the gap (to separate the rule-center position from the gap-center position)

Example of row-rule-align in a grid container.

You might be wondering if there’s a bug in the bottom-right example. Why is the gap-over not honored there? That’s a non-interior rule edge and it’s controlled separately with row-rule-edge-align, see below.

### 5.2. The column-rule-edge-align and row-rule-edge-align Properties

Name: | column-rule-edge-align, row-rule-edge-align
Value: | [gap | gap-center | gap-over]{1,2}
Initial: | gap
Applies to: | multi-column containers, flex containers, grid containers, table and table-row-group containers
Inherited: | no
Percentages: | N/A
Computed value: | the specified value
Canonical order: | per grammar
Animation type: | discrete

These properties specify the start/end attachment point of the rule containing rectangle in the longitudinal axis for the outer edges only. That is, the start edge of the first rule and the end edge of the last rule (which may be the same rule). The start value is specified first, the end value second. If only one value is specified it is used for both start and end. (Attachment points for the interior rule edges are specified with the *-rule-align properties above.)

Note: The rule/rule-center/rule-over keywords are omitted here (compared with column-rule-align) since there are no rules in the edge gutters.

The figure below illustrates the alignment values. The red values are used for the top column rule’s start edge and the yellow values are used for its end edge. The yellow values are also used for the bottom column rule’s start edge. However, in this case the roles of gap / gap-over and rule / rule-over are swapped. It’s only the center values that are shared. Also note that gap-center isn’t necessarily aligned with rule-center. In this case they aren’t aligned because the row rule (purple) is using a lateral start inset. The cyan colored values are used for the bottom column border’s end edge. (If the top border were to stretch over the entire grid, then they would be used for its end edge.)

column-rule-edge-align controls which of the red and cyan colored attachment points should be used. column-rule-edge-align the yellow colored ones (and all other interior edges if there were more rows).

Illustration of rule alignment values.

Here’s the rule styling used for the above example:

        column-rule: 14px solid blue;
        column-rule-align: rule-center rule;
        column-rule-edge-align: gap-center gap-over;

        row-rule: 16px solid #7000ff;
        row-rule-lateral-inset-start: 30px;

The alignment points follow the same pattern in the other axis for the row rules. In this case the row rule is using the initial values (gap) so they align with the inline axis gap edges.

Are there use cases for other box-related edge attachment points? e.g. 'padding | padding-center | padding-over | border...'

## 6. Rule Extent

### 6.1. The column-rule-extent and row-rule-extent Properties

Name: | column-rule-extent, row-rule-extent
Value: | [segment | start | end | short | long | all-start | all-end | all-short | all-long ] allow-overlap?
Initial: | long
Applies to: | multi-column containers, flex containers, grid containers, table and table-row-group containers
Inherited: | no
Percentages: | N/A
Computed value: | the specified value
Canonical order: | per grammar
Animation type: | discrete

perhaps make all a separate keyword? like so: [segment | [[start | end | short | long] all?] ] allow-overlap?

These properties specify the extent of the rule in its longitudinal axis. segment is an abstract term to describe the distance between two consecutive gaps. An extent can cover one or more segments and the extent size is the distance between the start position of the first of those segments and the end position of the last segment. We’ll define segment in more detail in the container-specific sub-sections that follow.

The allow-overlap only affects rules in grid and table layout with spanning items/cells. It controls whether a rule should continue through such a span.

Note: It’s only an item’s grid span that are considered when determining if an item is spanning or not, not its layout position or size.

The all-* values makes a rule extend over all segments in an axis, subject to not being interrupted by a span. In grid and table layout, where the tracks/table groups/rows all have the same length in a rule’s longitudinal axis, all the all-* have the same behavior. They are intended for flexbox and masonry layout, where the gaps may fall at different positions in adjacent flex lines and masonry tracks.

The lateral position of a rule is determined by its first segment.

The following sub-sections will describe the rule extent for each type of layout container in more detail.

#### 6.1.1. Grid Containers

In a grid container, gaps are placed between tracks, so the segment value maps to the extent of a grid cell.

This example illustrates segment rules. Note that rules are generated in all gaps, whether there are items in a grid cell or not.

Example of column and row rules with segment extent in a grid container.

Collapsed tracks don’t count -- they don’t generate gaps and thus don’t have gap rules. They generally behave as if they don’t exist as far as rules are concerned. The example below also illustrates that the position and size of the items don’t affect the rules; it’s only the position and size of the grid cells that count.

Example of column and row rules with in a grid container with collapsed tracks.

Rules behave symmetrically in the grid axes, but a masonry axis in a masonry grid layout behaves differently; we’ll cover that case in a separate section later.

In a grid axis, rules are created between adjacent (non-collapsed) tracks and their extent sizes are controlled by the column-rule-extent/row-rule-extent values as follows:

segment
  the extent size is the size of grid cell in the relevant axis
start
  the extent size is the size of the next grid cell span in the start-most of the two adjacent tracks
end
  the extent size is the size of the next grid cell span in the end-most of the two adjacent tracks
short
  the extent size is the smaller of the next grid cell span sizes of the two adjacent tracks
long
  the extent size is the larger of the next grid cell span sizes of the two adjacent tracks
all-start, all-end, all-short, all-long
  the extent size is the length of the track in the relevant axis (they all behave the same because all tracks in a grid axis have the same size)
allow-overlap
  controls whether the next grid cell span stops short of a cell which has an item spanning over the gap (see the algorithm below)

The following algorithm determines the rule segments to create in an axis and their extent sizes. For each pair of adjacent tracks, we first find the next grid cell span for each track. Then select one of those per the property values above.

For each pair of adjacent tracks, start by setting each track’s current cell to be its first cell in the implicit grid, then:

1. if allow-overlap was not specified, and the current cell in the start-most of the pair of tracks contains an item that spans into the end-most of the tracks, then skip this cell and let the current cell of each track be the cell after it, then go to step 1 or exit if there are no more cells
2. if the *-rule-extent is one of the all-* values, then the next grid cell span is the span of cells from the current cell to last cell in the track (inclusive); if allow-overlap was not specified, then stop before the first (opposite axis) track that contains an item spanning between this pair of tracks
3. otherwise, if the current cell is empty, or *-rule-extent is segment, then the next grid cell span of that track is the current cell
4. otherwise, if the current cell contains items that are spanning in the same axis, then that track’s next grid cell span is the longest of those spans; if allow-overlap was not specified, then stop before the first (opposite axis) track that contains an item spanning between this pair of tracks
5. create a rule segment with the following extent size:
   1. for short(long), the extent size is the length of the shortest(longest) of the two next grid cell spans
   2. for start(end), the extent size is the length of the next grid cell span of the start-most(end-most) track
   3. for all-*, the extent size is the length of the next grid cell span (which is always the same for the two tracks)
6. set the current cell to the next cell, in each track, that is after the last cell of the next grid cell span that we picked in the steps above; exit if there are no more cells; otherwise, go to step 1.

This example demonstrates the difference between the row-rule-extent values in a grid with spanning items. The grid has seven columns. The grid items are semi-transparent to show any rules or overlapping items under them. Item 7 for example has grid-column: 2 / span 3 and item 3 has grid-row: 1 / span 2. They are both forced to span into the cell in row 2, column 4 to illustrate what happens when items span like this.
Examples of row-rule-extent in a grid container.

##### 6.1.1.1. Subgrid

A subgrid creates its own set of gap rules. It uses its own gaps, which are centered with, but may have a different size than the ancestor grid(s), as described in subgrids. Other than that, rules are created inside a subgrid in the same way as in a regular grid.

A grid item that is a subgrid affects its parent grid’s rule formation exactly as a regular non-subgrid item would (whether the parent is also a subgrid or not), i.e. its span (if any) affects the algorithm above in the same way.

allow-overlap can be used in the parent to extend its rules under the subgrid. The subgrid’s rules, if any, are rendered by the subgrid and thus render on top of the parent, as usual.

When the subgrid determines its rule extents, it does not consider any items that aren’t its own grid items, i.e. any items in an ancestor grid that have been placed into the same grid cell that the subgrid occupies are not considered. Furthermore, it only uses its own local gap and rule metrics for positioning and sizing its rules. It doesn’t consider any gaps or rules that originate outside of the subgrid.

This example illustrates that a subgrid uses its own local gap and rule metrics for positioning and sizing its rules. It also shows what happens when a parent rule crosses a subgrid item.

Note that the parent’s column rule passing through the subgrid is not used for the row-rule-align: rule in the subgrid. The subgrid is in fact completely unaware of any parent rules.

Example of gap rules in a subgrid.

##### 6.1.1.2. Masonry

Masonry layout has one grid axis (which may be subgridded) and one masonry axis. The grid axis works the same as has been described above. The masonry axis is special since an item is placed into a grid track based on the layout size of the items before it, so they are typically not aligned over the tracks. Furthermore, the grid tracks may have a different start position (due to masonry axis alignment) and size.

This example illustrates a few variations of rules in a masonry grid layout. All the grids have column-rule-edge-align: gap-over to extend the edge rules out to the content-box edge.
Example of gap rules in a masonry grid.
This example illustrates some of the column-rule-extent: all-* values.
Example of gap rules in a masonry grid.

TODO: add definition list and algorithm here...

is it useful to be able to create a rule extent for the intersection or union between two tracks, like so: It’s pretty easy to implement, fwiw... (I accidently implemented short/long like that before I realized it was inconsistent with how they work elsewhere). I think it’s a case that is unique to a masonry axis though, at least currently...

#### 6.1.2. Flex Containers

In a row-oriented flex container, the row-rule-* properties creates rules between flex lines, and the column-rule-* properties creates rules between flex items within a flex line.

In column-oriented flex container, the roles of row-rule-extent and column-rule-extent are swapped. For the rest of this sub-section we will describe the row-oriented case (just swap column/row in the text below to get the column-oriented case).

Flex items can’t span multiple lines so there are no collisions possible for the main axis rules, hence the allow-overlap keyword is ignored in flex layout in the main axis. A subsequent flex line is considered as a collision for the cross axis rules, i.e. a cross axis rule has the extent of one flex line, unless allow-overlap is used (together with one the all-* values). The reason is that items in different lines typically don’t line up in a way that the gaps between items are aligned across the lines (unless an author is very careful to arrange that), so this is to have a safe default behavior.

all-long allow-overlap can be used to override that and the extent size is then from the cross axis start edge of the first flex line to the cross axis end edge of the last flex line (all the all-* behave the same). Only the first flex line creates column rules in this case, and the rule’s lateral position is taken from the gap in the first line.

Authors are advised to not use the allow-overlap value in the main axis of a multi-line flex container since it’s likely to make items on subsequent lines overlap the rules. It may be used when all flex items are guaranteed to have the exact same main axis outer size and align such that the gaps are aligned between all the lines.

Rules are created between adjacent flex lines, and their extent sizes are controlled by the row-rule-extent values defined as follows:

segment
  behaves as short
start
  use the outer size of the items in the flex line on the block axis start side
end
  use the outer size of the items in the flex line on the block axis end side
short
  use the outer size of the next flex line item which has the smaller size (see detailed algorithm below)
long
  use the outer size of the next flex line item which has the larger size (see detailed algorithm below)
all-start
  the distance between the start position of the first item to the end position of the last item on the start side flex line
all-end
  the distance between the start position of the first item to the end position of the last item on the end side flex line
all-short
  the distance between the end-most start position of the first item on each flex line to the start-most end position of the last item on each flex line
all-long
  the distance between the start-most start position of the first item on each flex line to the end-most end position of the last item on each flex line
allow-overlap
  is ignored in this axis since flex items can’t span between flex lines so there are no collisions (as defined in this spec)

The next flex line item is assigned by the following algorithm. For each pair of adjacent flex lines, start with assigning the next flex line item to the first item (in order-modified document order) on the respective line, then:

0. exit if neither line has a next flex line item
1. 1. if only one line has a next flex line item then pick that item and go to 2
   2. if either of the two next flex line items has a start position that is beyond the other item’s end position, then pick the start-most item and go to 2.
   3. otherwise, pick the item with the smallest(largest) outer size for short(long)
2. use the picked item’s outer size as this rule segment’s extent size, then change the next flex line item for the picked item’s line to the next item on its line
3. assign the next flex line item for the other line to the next item on this line that has an inline start position that is greater than the end position of the picked item

(start/end position and sizes above are referring to the item’s margin-box in the rule’s longitudinal axis; the phrase "next item" refers to the next item in order-modified document order)

Here are a few examples to illustrate the row-rule-extent values.
A row-rule-extent: start example.
A row-rule-extent: end example.
A row-rule-extent: long example.
A row-rule-extent: all-short example.
A row-rule-extent: all-long example.
This is an example to illustrate what happens when an column-rule-extent: all-long allow-overlap rule is used and the gaps aren’t aligned. (The flex items are semi-transparent to show the column rules underneath).
A column-rule-extent: all-long allow-overlap example.

#### 6.1.3. Table Containers

A table container creates rules between its table-column-groups and table-row-groups. Collapsed column-groups and row-groups are treated as if they don’t exist. Column rules (between table-column-groups) collide with table-row-groups. Row rules (between table-row-groups) collide with table-column-groups. The allow-overlap can be used to create rules that extend over the entire column/row length. Given that all table-column-groups have the same block axis size and all table-row-groups have same the inline axis size, the short/long/start/end keywords behave the same. Ditto for the all-* keywords.

Note, column 2 is collapsed in this example.
An example of table rules.

sort out if non-collapsed column-groups that only contain collapsed columns should generate rules, ditto row-groups/rows

#### 6.1.4. Table Row Group Containers

A table-row-group container creates rules between its table-rows and between each table-cell in a row. Collapsed table-rows are treated as if they don’t exist. Collapsed table-columns are treated as if they don’t exist.

Row rules (between table-rows) collide with cells that have a row span crossing it. Column rules (between table-cells) collide with cells that have a column span crossing it. allow-overlap can be used to create rules that extend over such spanning cells.

This example illustrates rules between table rows and cells. And also what happens when the table rules from the last example is also applied.
Example of table row and cell rules.

visibility:collapse on table-cells does not affect the rules in any way.

#### 6.1.5. Multi-Column Containers

Multi-column containers already support rendering column rules between their columns. That’s now extended with all the new features described above. The changes described above are backwards-compatible with existing web content that use valid column-rule style values. Some previously invalid column-rule values are now valid though, which could cause problems. For example, column-rule-width: 100%, which previously would not parse, will now start doing something.

The row-rule-* properties apply to multi-column containers, and create row rules between multicol lines and spanners, separating them in the block axis.

The segments are the columns and the margin-box of spanners.

this proposal makes the assumption that the related proposal that row-gap should apply to multi-column containers is also adopted (issue #6746).

This example illustrates rules in a multi-column container.
Example of column and row rules in a multi-column.
If multi-column containers add support for 'column-span: <integer>' some time in the future, this is how row rules will work:
Example of column-span: 2 in a multi-column with column and row rules.

## 7. The Rule Containing Rectangle

The rule containing rectangle is formed by the rule extent and alignment in the longitudinal axis, and by the size of the gutter in the lateral axis. (For clarity, the size of the gutter is calculated from the gap properties plus any extra space contributed by alignment distribution but does not include any item margins.)

It is important to note that the rule containing rectangle’s size in an axis isn’t affected by any of the inset properties in the same axis as that would lead to a circular dependency when resolving inset percentage values. (The rule containing rectangle is the percentage basis for all the rule properties which take percentage values.) However, a rule that uses column-rule-align: rule | rule-center | rule-over is affected by the lateral inset properties of the rule it aligns to in the opposite axis.

Here’s an illustration of the rule containing rectangle (the dashed green rectangle) for the top blue rule. This is a 2x2 grid using the default extent, so the extent size is the row’s block size. It has the following non-default rule properties:

          column-rule: 14px solid blue;
          column-rule-align: rule;
          column-rule-edge-align: gap-center;
          column-rule-longitudinal-inset-end: 8px;

          row-rule: 6px solid black;
          row-rule-lateral-inset-start: 20px;

The Rule Containing Rectangle

Note that the rule containing rectangle extends to the start of the black horizontal rule, which has a 20px lateral inset (making it non-centered). We align to its start with column-rule-align: rule. From there, we move the bottom edge of the blue rule up by 8px with column-rule-longitudinal-inset-end: 8px. The default column-rule-length: auto then fills the resulting area. If we were to use column-rule-length: 100% here instead, then the rule would fill the rule containing rectangle vertically, since that’s its percentage basis. (The end inset would then be ignored since the start inset is zero by default so the situation is over-constrained, and we resolve by ignoring the end inset, per the sizing rules.)

## 8. Rule Painting Order

Column and row rules are painted in the same layer as the element’s border. They are painted after (on top of) the element’s border. All column rules for an element are painted first, then all of its row rules. The rules for an axis are painted in the order they were generated by the rule extent algorithms described above. Typically from the logical start to the end of the axis.

For table layout, all the table rules (in both axes) are painted before the rules for the row-groups. The painting order between multiple row-groups is whatever the table spec specifies. For an individual row-group, the rules are painted in logical start to end order in both axes.

Again, note that for a specific fragment, all the column rules are painted before all the row rules, the above merely tries to clarify the painting order of the rules for a specific axis.

## 9. Rule Overflow

The column and row rule areas contributes to a fragment’s ink overflow. Note that they can overflow an fragment’s border-box due to negative inset values etc.

Here’s an example showing rules that overflow their container and how they are clipped. Both grids have large negative insets to extend the rules outside of the container. The right grid has overflow: hidden which clips its rules at the padding area edge.
Examples of rule overflow and clipping.

For clarity, none of the properties in this spec affects layout in any way. Column and row rules are purely a painting effect.

## Conformance

### Document conventions

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:

This is an example of an informative example.

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.

Tests

Tests relating to the content of this specification may be documented in “Tests” blocks like this one. Any such block is non-normative.

### Conformance classes

Conformance to this specification is defined for three conformance classes:

style sheet
  A CSS style sheet.
renderer
  A UA that interprets the semantics of a style sheet and renders documents that use them.
authoring tool
  A UA that writes a style sheet.

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.

### Partial implementations

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 component 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.

#### Implementations of Unstable and Proprietary Features

To avoid clashes with future stable CSS features, the CSSWG recommends following best practices for the implementation of unstable features and proprietary extensions to CSS.

### Non-experimental implementations

Once a specification reaches the Candidate Recommendation stage, non-experimental implementations are possible, and implementors should release an unprefixed implementation of any CR-level feature they can demonstrate to be correctly implemented according to spec.

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.

Further information on submitting testcases and implementation reports can be found from on the CSS Working Group’s website at http://www.w3.org/Style/CSS/Test/. Questions should be directed to the public-css-testsuite@w3.org mailing list.

## Index

### Terms defined by this specification

- all-end, in § 6.1.1
- all-long, in § 6.1.1
- allow-overlap, in § 6.1.1
- all-short, in § 6.1.1
- all-start, in § 6.1.1
- column-rule-align, in § 5.1
- column-rule-edge-align, in § 5.2
- column-rule-extent, in § 6.1
- column-rule-image, in § 2.4
- column-rule-image-repeat, in § 2.3
- column-rule-image-slice, in § 2.2
- column-rule-image-source, in § 2.1
- column-rule-lateral-inset, in § 3.5
- column-rule-lateral-inset-end, in § 3.3
- column-rule-lateral-inset-start, in § 3.3
- column-rule-length, in § 3.2
- column-rule-longitudinal-edge-inset, in § 3.9
- column-rule-longitudinal-edge-inset-end, in § 3.8
- column-rule-longitudinal-edge-inset-start, in § 3.8
- column-rule-longitudinal-inset, in § 3.7
- column-rule-longitudinal-inset-end, in § 3.6
- column-rule-longitudinal-inset-start, in § 3.6
- end, in § 6.1.1
- extent size, in § 6.1
- lateral axis, in § 1.3
- long, in § 6.1.1
- longitudinal axis, in § 1.3
- next flex line item, in § 6.1.2
- next grid cell span, in § 6.1.1
- <number [0,∞]>, in § 2.2
- <percentage [0,∞]>, in § 2.2
- repeat, in § 2.3
- round, in § 2.3
- row-rule, in § 4.2
- row-rule-align, in § 5.1
- row-rule-color, in § 4.1
- row-rule-edge-align, in § 5.2
- row-rule-extent, in § 6.1
- row-rule-image, in § 2.4
- row-rule-image-repeat, in § 2.3
- row-rule-image-slice, in § 2.2
- row-rule-image-source, in § 2.1
- row-rule-lateral-inset, in § 3.5
- row-rule-lateral-inset-end, in § 3.3
- row-rule-lateral-inset-start, in § 3.3
- row-rule-length, in § 3.2
- row-rule-longitudinal-edge-inset, in § 3.9
- row-rule-longitudinal-edge-inset-end, in § 3.8
- row-rule-longitudinal-edge-inset-start, in § 3.8
- row-rule-longitudinal-inset, in § 3.7
- row-rule-longitudinal-inset-end, in § 3.6
- row-rule-longitudinal-inset-start, in § 3.6
- row-rule-style, in § 4.1
- row-rule-width, in § 3.1
- rule containing rectangle, in § 7
- rule length, in § 1.3
- segment
  - definition of, in § 6.1
  - value for row-rule-extent, in § 6.1.1
- short, in § 6.1.1
- space, in § 2.3
- start, in § 6.1.1
- stretch, in § 2.3

https://drafts.csswg.org/css-backgrounds-3/#typedef-line-style Referenced in:

- 4.1. The row-rule-style and row-rule-color Properties

https://drafts.csswg.org/css-backgrounds-3/#typedef-line-width Referenced in:

- 3.1. The column-rule-width and row-rule-width Properties (2) (3)

https://drafts.csswg.org/css-backgrounds-3/#propdef-border-style Referenced in:

- 2. Rule Images and Gradients

https://drafts.csswg.org/css-box-4/#valdef-margin-trim-all Referenced in:

- 6.1. The column-rule-extent and row-rule-extent Properties

https://drafts.csswg.org/css-box-4/#valdef-box-margin-box Referenced in:

- 6.1.5. Multi-Column Containers

https://drafts.csswg.org/css-cascade-5/#used-value Referenced in:

- 3.1. The column-rule-width and row-rule-width Properties
- 3.2. The column-rule-length and row-rule-length Properties
- 3.3. The Rule Lateral Inset Properties
- 3.6. The Rule Longitudinal Inset Properties

https://drafts.csswg.org/css-color-4/#typedef-color Referenced in:

- 4.1. The row-rule-style and row-rule-color Properties

https://drafts.csswg.org/css-color-4/#propdef-opacity Referenced in:

- 3.6. The Rule Longitudinal Inset Properties

https://drafts.csswg.org/css-display-3/#order-modified-document-order Referenced in:

- 6.1.2. Flex Containers (2)

https://drafts.csswg.org/css-flexbox-1/#flex-container Referenced in:

- 1.1. Overview
- 2.1. The column-rule-image-source and row-rule-image-source Properties
- 2.2. The column-rule-image-slice and row-rule-image-slice Properties
- 2.3. The column-rule-image-repeat and row-rule-image-repeat Properties
- 2.4. The column-rule-image and row-rule-image Shorthands
- 3.1. The column-rule-width and row-rule-width Properties (2)
- 3.2. The column-rule-length and row-rule-length Properties
- 3.3. The Rule Lateral Inset Properties
- 3.6. The Rule Longitudinal Inset Properties
- 3.8. The Rule Longitudinal Edge Inset Properties
- 4.1. The row-rule-style and row-rule-color Properties (2)
- 5.1. The column-rule-align and row-rule-align Properties
- 5.2. The column-rule-edge-align and row-rule-edge-align Properties
- 6.1. The column-rule-extent and row-rule-extent Properties

https://drafts.csswg.org/css-grid-2/#collapsed-track Referenced in:

- 6.1.1. Grid Containers (2)

https://drafts.csswg.org/css-grid-2/#grid Referenced in:

- 6.1.1. Grid Containers

https://drafts.csswg.org/css-grid-2/#grid-cell Referenced in:

- 6.1.1. Grid Containers (2) (3)

https://drafts.csswg.org/css-grid-2/#grid-container Referenced in:

- 1.1. Overview
- 2.1. The column-rule-image-source and row-rule-image-source Properties
- 2.2. The column-rule-image-slice and row-rule-image-slice Properties
- 2.3. The column-rule-image-repeat and row-rule-image-repeat Properties
- 2.4. The column-rule-image and row-rule-image Shorthands
- 3.1. The column-rule-width and row-rule-width Properties (2)
- 3.2. The column-rule-length and row-rule-length Properties
- 3.3. The Rule Lateral Inset Properties
- 3.6. The Rule Longitudinal Inset Properties
- 3.8. The Rule Longitudinal Edge Inset Properties
- 4.1. The row-rule-style and row-rule-color Properties (2)
- 5.1. The column-rule-align and row-rule-align Properties
- 5.2. The column-rule-edge-align and row-rule-edge-align Properties
- 6.1. The column-rule-extent and row-rule-extent Properties
- 6.1.1. Grid Containers

https://drafts.csswg.org/css-grid-2/#propdef-grid-column Referenced in:

- 6.1.1. Grid Containers

https://drafts.csswg.org/css-grid-2/#propdef-grid-row Referenced in:

- 6.1.1. Grid Containers

https://drafts.csswg.org/css-grid-2/#implicit-grid Referenced in:

- 6.1.1. Grid Containers

https://drafts.csswg.org/css-grid-2/#subgrid Referenced in:

- 6.1.1.2. Masonry

https://drafts.csswg.org/css-grid-3/#masonry-axis Referenced in:

- 6.1.1. Grid Containers
- 6.1.1.2. Masonry (2)

https://drafts.csswg.org/css-images-3/#typedef-image Referenced in:

- 2.1. The column-rule-image-source and row-rule-image-source Properties (2) (3)

https://drafts.csswg.org/css-images-3/#default-object-size Referenced in:

- 2.2. The column-rule-image-slice and row-rule-image-slice Properties

https://drafts.csswg.org/css-images-3/#specified-size Referenced in:

- 2.2. The column-rule-image-slice and row-rule-image-slice Properties

https://drafts.csswg.org/css-multicol-1/#propdef-column-rule-width Referenced in:

- 1.1. Overview
- 1.2. Module Interactions
- 3.1. The column-rule-width and row-rule-width Properties (2)
- 6.1.5. Multi-Column Containers

https://drafts.csswg.org/css-multicol-1/#multi-column-container Referenced in:

- 1.1. Overview
- 2.1. The column-rule-image-source and row-rule-image-source Properties
- 2.2. The column-rule-image-slice and row-rule-image-slice Properties
- 2.3. The column-rule-image-repeat and row-rule-image-repeat Properties
- 2.4. The column-rule-image and row-rule-image Shorthands
- 3.1. The column-rule-width and row-rule-width Properties (2)
- 3.2. The column-rule-length and row-rule-length Properties
- 3.3. The Rule Lateral Inset Properties
- 3.6. The Rule Longitudinal Inset Properties
- 3.8. The Rule Longitudinal Edge Inset Properties
- 4.1. The row-rule-style and row-rule-color Properties (2)
- 5.1. The column-rule-align and row-rule-align Properties
- 5.2. The column-rule-edge-align and row-rule-edge-align Properties
- 6.1. The column-rule-extent and row-rule-extent Properties
- 6.1.5. Multi-Column Containers (2) (3)

https://drafts.csswg.org/css-multicol-1/#multi-column-layout Referenced in:

- 3.6. The Rule Longitudinal Inset Properties

https://drafts.csswg.org/css-multicol-1/#spanner Referenced in:

- 6.1.5. Multi-Column Containers (2)

https://drafts.csswg.org/css-multicol-2/#propdef-column-span Referenced in:

- 6.1.5. Multi-Column Containers

https://drafts.csswg.org/css-overflow-3/#ink-overflow Referenced in:

- 9. Rule Overflow

https://drafts.csswg.org/css-overflow-3/#propdef-overflow Referenced in:

- 9. Rule Overflow

https://drafts.csswg.org/css-position-3/#propdef-left Referenced in:

- 3.3. The Rule Lateral Inset Properties

https://drafts.csswg.org/css-position-3/#propdef-right Referenced in:

- 3.3. The Rule Lateral Inset Properties

https://drafts.csswg.org/css-sizing-3/#outer-size Referenced in:

- 6.1.2. Flex Containers (2) (3) (4) (5) (6) (7)

https://drafts.csswg.org/css-sizing-3/#propdef-width Referenced in:

- 3.3. The Rule Lateral Inset Properties

https://drafts.csswg.org/css-tables-3/#span Referenced in:

- 6.1.4. Table Row Group Containers (2)

https://drafts.csswg.org/css-tables-3/#table Referenced in:

- 1.1. Overview
- 2.1. The column-rule-image-source and row-rule-image-source Properties
- 2.2. The column-rule-image-slice and row-rule-image-slice Properties
- 2.3. The column-rule-image-repeat and row-rule-image-repeat Properties
- 2.4. The column-rule-image and row-rule-image Shorthands
- 3.1. The column-rule-width and row-rule-width Properties (2)
- 3.2. The column-rule-length and row-rule-length Properties
- 3.3. The Rule Lateral Inset Properties
- 3.6. The Rule Longitudinal Inset Properties
- 3.8. The Rule Longitudinal Edge Inset Properties
- 4.1. The row-rule-style and row-rule-color Properties (2)
- 5.1. The column-rule-align and row-rule-align Properties
- 5.2. The column-rule-edge-align and row-rule-edge-align Properties
- 6.1. The column-rule-extent and row-rule-extent Properties
- 6.1.3. Table Containers
- 8. Rule Painting Order

https://drafts.csswg.org/css-tables-3/#table-cell Referenced in:

- 6.1.4. Table Row Group Containers (2)

https://drafts.csswg.org/css-tables-3/#table-column Referenced in:

- 6.1.4. Table Row Group Containers

https://drafts.csswg.org/css-tables-3/#table-column-group Referenced in:

- 6.1.3. Table Containers (2) (3) (4)

https://drafts.csswg.org/css-tables-3/#table-row Referenced in:

- 6.1.4. Table Row Group Containers (2) (3)

https://drafts.csswg.org/css-tables-3/#table-row-group Referenced in:

- 1.1. Overview
- 2.1. The column-rule-image-source and row-rule-image-source Properties
- 2.2. The column-rule-image-slice and row-rule-image-slice Properties
- 2.3. The column-rule-image-repeat and row-rule-image-repeat Properties
- 2.4. The column-rule-image and row-rule-image Shorthands
- 3.1. The column-rule-width and row-rule-width Properties (2)
- 3.2. The column-rule-length and row-rule-length Properties
- 3.3. The Rule Lateral Inset Properties
- 3.6. The Rule Longitudinal Inset Properties
- 3.8. The Rule Longitudinal Edge Inset Properties
- 4.1. The row-rule-style and row-rule-color Properties (2)
- 5.1. The column-rule-align and row-rule-align Properties
- 5.2. The column-rule-edge-align and row-rule-edge-align Properties
- 6.1. The column-rule-extent and row-rule-extent Properties
- 6.1.3. Table Containers (2) (3) (4)
- 6.1.4. Table Row Group Containers

https://drafts.csswg.org/css-values-4/#integer-value Referenced in:

- 6.1.5. Multi-Column Containers

https://drafts.csswg.org/css-values-4/#typedef-length-percentage Referenced in:

- 3.2. The column-rule-length and row-rule-length Properties
- 3.3. The Rule Lateral Inset Properties
- 3.6. The Rule Longitudinal Inset Properties
- 3.8. The Rule Longitudinal Edge Inset Properties

https://drafts.csswg.org/css-values-4/#number-value Referenced in:

- 2.2. The column-rule-image-slice and row-rule-image-slice Properties (2)

https://drafts.csswg.org/css-values-4/#percentage-value Referenced in:

- 1.2. Module Interactions
- 2.2. The column-rule-image-slice and row-rule-image-slice Properties (2)
- 3.1. The column-rule-width and row-rule-width Properties (2)

https://drafts.csswg.org/css-values-4/#mult-opt Referenced in:

- 3.5. The column-rule-lateral-inset and row-rule-lateral-inset Shorthands (2)
- 3.7. The column-rule-longitudinal-inset and row-rule-longitudinal-inset Shorthands (2)
- 3.9. The column-rule-longitudinal-edge-inset and row-rule-longitudinal-edge-inset Shorthands (2)
- 6.1. The column-rule-extent and row-rule-extent Properties

https://drafts.csswg.org/css-values-4/#mult-num-range Referenced in:

- 2.2. The column-rule-image-slice and row-rule-image-slice Properties
- 5.1. The column-rule-align and row-rule-align Properties
- 5.2. The column-rule-edge-align and row-rule-edge-align Properties

https://drafts.csswg.org/css-values-4/#comb-one Referenced in:

- 2.1. The column-rule-image-source and row-rule-image-source Properties
- 2.2. The column-rule-image-slice and row-rule-image-slice Properties
- 2.3. The column-rule-image-repeat and row-rule-image-repeat Properties (2) (3)
- 3.1. The column-rule-width and row-rule-width Properties (2) (3)
- 3.2. The column-rule-length and row-rule-length Properties
- 3.3. The Rule Lateral Inset Properties
- 3.6. The Rule Longitudinal Inset Properties
- 3.8. The Rule Longitudinal Edge Inset Properties
- 5.1. The column-rule-align and row-rule-align Properties (2) (3) (4) (5)
- 5.2. The column-rule-edge-align and row-rule-edge-align Properties (2)
- 6.1. The column-rule-extent and row-rule-extent Properties (2) (3) (4) (5) (6) (7) (8)

https://drafts.csswg.org/css-values-4/#comb-any Referenced in:

- 2.4. The column-rule-image and row-rule-image Shorthands (2)
- 4.2. The row-rule Shorthand (2)

https://drafts.csswg.org/css-writing-modes-4/#propdef-writing-mode Referenced in:

- 1.3. Definitions

### Terms defined by reference

- [css-backgrounds-3] defines the following terms:
  - <line-style>
  - <line-width>
  - border-style
- [css-box-4] defines the following terms:
  - all
  - margin-box
- [css-cascade-5] defines the following terms:
  - used value
- [css-color-4] defines the following terms:
  - <color>
  - opacity
- [css-display-3] defines the following terms:
  - order-modified document order
- [css-flexbox-1] defines the following terms:
  - flex container
- [css-grid-2] defines the following terms:
  - collapsed track
  - grid
  - grid cell
  - grid container
  - grid-column
  - grid-row
  - implicit grid
  - subgrid
- [css-grid-3] defines the following terms:
  - masonry axis
- [css-images-3] defines the following terms:
  - <image>
  - default object size
  - specified size
- [css-multicol-1] defines the following terms:
  - column-rule-width
  - multi-column container
  - multi-column layout
  - spanner
- [css-multicol-2] defines the following terms:
  - column-span
- [css-overflow-3] defines the following terms:
  - ink overflow
  - overflow
- [css-position-3] defines the following terms:
  - left
  - right
- [css-sizing-3] defines the following terms:
  - outer size
  - width
- [css-tables-3] defines the following terms:
  - span
  - table
  - table-cell
  - table-column
  - table-column-group
  - table-row
  - table-row-group
- [css-values-4] defines the following terms:
  - <integer>
  - <length-percentage>
  - <number>
  - <percentage>
  - ?
  - {a,b}
  - |
  - ||
- [css-writing-modes-4] defines the following terms:
  - writing-mode

## References

### Normative References

[CSS-BACKGROUNDS-3]
  Bert Bos; Elika Etemad; Brad Kemper. CSS Backgrounds and Borders Module Level 3. 26 July 2021. CR. URL: https://www.w3.org/TR/css-backgrounds-3/
[CSS-BOX-4]
  Elika Etemad. CSS Box Model Module Level 4. 21 April 2020. WD. URL: https://www.w3.org/TR/css-box-4/
[CSS-CASCADE-5]
  Elika Etemad; Miriam Suzanne; Tab Atkins Jr.. CSS Cascading and Inheritance Level 5. 15 October 2021. WD. URL: https://www.w3.org/TR/css-cascade-5/
[CSS-COLOR-4]
  Tab Atkins Jr.; Chris Lilley. CSS Color Module Level 4. 1 June 2021. WD. URL: https://www.w3.org/TR/css-color-4/
[CSS-DISPLAY-3]
  Tab Atkins Jr.; Elika Etemad. CSS Display Module Level 3. 3 September 2021. CR. URL: https://www.w3.org/TR/css-display-3/
[CSS-FLEXBOX-1]
  Tab Atkins Jr.; et al. CSS Flexible Box Layout Module Level 1. 19 November 2018. CR. URL: https://www.w3.org/TR/css-flexbox-1/
[CSS-GRID-2]
  Tab Atkins Jr.; Elika Etemad; Rossen Atanassov. CSS Grid Layout Module Level 2. 18 December 2020. CR. URL: https://www.w3.org/TR/css-grid-2/
[CSS-GRID-3]
  CSS Grid Layout Level 3 URL: https://drafts.csswg.org/css-grid-3/
[CSS-IMAGES-3]
  Tab Atkins Jr.; Elika Etemad; Lea Verou. CSS Images Module Level 3. 17 December 2020. CR. URL: https://www.w3.org/TR/css-images-3/
[CSS-MULTICOL-1]
  Florian Rivoal; Rachel Andrew. CSS Multi-column Layout Module Level 1. 12 October 2021. CR. URL: https://www.w3.org/TR/css-multicol-1/
[CSS-OVERFLOW-3]
  David Baron; Elika Etemad; Florian Rivoal. CSS Overflow Module Level 3. 3 June 2020. WD. URL: https://www.w3.org/TR/css-overflow-3/
[CSS-SIZING-3]
  Tab Atkins Jr.; Elika Etemad. CSS Box Sizing Module Level 3. 17 March 2021. WD. URL: https://www.w3.org/TR/css-sizing-3/
[CSS-TABLES-3]
  François Remy; Greg Whitworth; David Baron. CSS Table Module Level 3. 27 July 2019. WD. URL: https://www.w3.org/TR/css-tables-3/
[CSS-VALUES-4]
  Tab Atkins Jr.; Elika Etemad. CSS Values and Units Module Level 4. 16 October 2021. WD. URL: https://www.w3.org/TR/css-values-4/
[CSS-WRITING-MODES-4]
  Elika Etemad; Koji Ishii. CSS Writing Modes Level 4. 30 July 2019. CR. URL: https://www.w3.org/TR/css-writing-modes-4/
[RFC2119]
  S. Bradner. Key words for use in RFCs to Indicate Requirement Levels. March 1997. Best Current Practice. URL: https://datatracker.ietf.org/doc/html/rfc2119

### Informative References

[CSS-MULTICOL-2]
  CSS Multi-column Layout Module Level 2 URL: https://drafts.csswg.org/css-multicol-2/
[CSS-POSITION-3]
  Elika Etemad; et al. CSS Positioned Layout Module Level 3. 19 May 2020. WD. URL: https://www.w3.org/TR/css-position-3/

## Property Index

Name | Value | Initial | Applies to | Inh. | %ages | Animation type | Canonical order | Computed value
--- | --- | --- | --- | --- | --- | --- | --- | ---
column-rule-align | [gap | gap-center | gap-over | rule | rule-center | rule-over]{1,2} | gap | multi-column containers, flex containers, grid containers, table and table-row-group containers | no | N/A | discrete | per grammar | the specified value
column-rule-edge-align | [gap | gap-center | gap-over]{1,2} | gap | multi-column containers, flex containers, grid containers, table and table-row-group containers | no | N/A | discrete | per grammar | the specified value
column-rule-extent | [segment | start | end | short | long | all-start | all-end | all-short | all-long ] allow-overlap? | long | multi-column containers, flex containers, grid containers, table and table-row-group containers | no | N/A | discrete | per grammar | the specified value
column-rule-image | <'column-rule-image-source'> || <'column-rule-image-slice'> || <'column-rule-image-repeat'> | see individual properties | multi-column containers, flex containers, grid containers, table and table-row-group containers | see individual properties | see individual properties | see individual properties | per grammar | see individual properties
column-rule-image-repeat | stretch | repeat | round | space | stretch | multi-column containers, flex containers, grid containers, table and table-row-group containers | no | N/A | discrete | per grammar | the specified keyword
column-rule-image-slice | [<number [0,∞]> | <percentage [0,∞]>]{1,2} | 0 | multi-column containers, flex containers, grid containers, table and table-row-group containers | no | refer to image size in the rule’s longitudinal axis | discrete | per grammar | one or two values, each either a number or percentage
column-rule-image-source | none | <image> | none | multi-column containers, flex containers, grid containers, table and table-row-group containers | no | N/A | discrete | per grammar | the keyword none or the computed <image>
column-rule-lateral-inset | <'column-rule-lateral-inset-start'> <'column-rule-lateral-inset-end'>? | see individual properties | see individual properties | see individual properties | see individual properties | see individual properties | per grammar | see individual properties
column-rule-lateral-inset-end | <length-percentage> | auto | auto | multi-column containers, flex containers, grid containers, table and table-row-group containers | no | refer to the rule containing rectangle’s size in the rule’s lateral axis | by computed value type | per grammar | the specified value
column-rule-lateral-inset-start | <length-percentage> | auto | auto | multi-column containers, flex containers, grid containers, table and table-row-group containers | no | refer to the rule containing rectangle’s size in the rule’s lateral axis | by computed value type | per grammar | the specified value
column-rule-length | <length-percentage> | auto | auto | multi-column containers, flex containers, grid containers, table and table-row-group containers | no | refer to the rule containing rectangle’s size in the rule’s longitudinal axis | by computed value type | per grammar | the specified value
column-rule-longitudinal-edge-inset | <'column-rule-longitudinal-edge-inset-start'> <'column-rule-longitudinal-edge-inset-end'>? | see individual properties | see individual properties | see individual properties | see individual properties | see individual properties | per grammar | see individual properties
column-rule-longitudinal-edge-inset-end | <length-percentage> | auto | 0 | multi-column containers, flex containers, grid containers, table and table-row-group containers | no | refer to the rule containing rectangle’s size in the rule’s longitudinal axis | by computed value type | per grammar | the specified value
column-rule-longitudinal-edge-inset-start | <length-percentage> | auto | 0 | multi-column containers, flex containers, grid containers, table and table-row-group containers | no | refer to the rule containing rectangle’s size in the rule’s longitudinal axis | by computed value type | per grammar | the specified value
column-rule-longitudinal-inset | <'column-rule-longitudinal-inset-start'> <'column-rule-longitudinal-inset-end'>? | see individual properties | see individual properties | see individual properties | see individual properties | see individual properties | per grammar | see individual properties
column-rule-longitudinal-inset-end | <length-percentage> | auto | 0 | multi-column containers, flex containers, grid containers, table and table-row-group containers | no | refer to the rule containing rectangle’s size in the rule’s longitudinal axis | by computed value type | per grammar | the specified value
column-rule-longitudinal-inset-start | <length-percentage> | auto | 0 | multi-column containers, flex containers, grid containers, table and table-row-group containers | no | refer to the rule containing rectangle’s size in the rule’s longitudinal axis | by computed value type | per grammar | the specified value
row-rule | <'row-rule-width'> || <'row-rule-style'> || <'row-rule-color'> | see individual properties | see individual properties | see individual properties | see individual properties | see individual properties | per grammar | see individual properties
row-rule-align | [gap | gap-center | gap-over | rule | rule-center | rule-over]{1,2} | gap | multi-column containers, flex containers, grid containers, table and table-row-group containers | no | N/A | discrete | per grammar | the specified value
row-rule-color | <color> | currentcolor | multi-column containers, flex containers, grid containers, table and table-row-group containers | no | N/A | by computed value type | per grammar | computed color
row-rule-edge-align | [gap | gap-center | gap-over]{1,2} | gap | multi-column containers, flex containers, grid containers, table and table-row-group containers | no | N/A | discrete | per grammar | the specified value
row-rule-extent | [segment | start | end | short | long | all-start | all-end | all-short | all-long ] allow-overlap? | long | multi-column containers, flex containers, grid containers, table and table-row-group containers | no | N/A | discrete | per grammar | the specified value
row-rule-image | <'column-rule-image-source'> || <'column-rule-image-slice'> || <'column-rule-image-repeat'> | see individual properties | multi-column containers, flex containers, grid containers, table and table-row-group containers | see individual properties | see individual properties | see individual properties | per grammar | see individual properties
row-rule-image-repeat | stretch | repeat | round | space | stretch | multi-column containers, flex containers, grid containers, table and table-row-group containers | no | N/A | discrete | per grammar | the specified keyword
row-rule-image-slice | [<number [0,∞]> | <percentage [0,∞]>]{1,2} | 0 | multi-column containers, flex containers, grid containers, table and table-row-group containers | no | refer to image size in the rule’s longitudinal axis | discrete | per grammar | one or two values, each either a number or percentage
row-rule-image-source | none | <image> | none | multi-column containers, flex containers, grid containers, table and table-row-group containers | no | N/A | discrete | per grammar | the keyword none or the computed <image>
row-rule-lateral-inset | <'row-rule-lateral-inset-start'> <'row-rule-lateral-inset-end'>? | see individual properties | see individual properties | see individual properties | see individual properties | see individual properties | per grammar | see individual properties
row-rule-lateral-inset-end | <length-percentage> | auto | auto | multi-column containers, flex containers, grid containers, table and table-row-group containers | no | refer to the rule containing rectangle’s size in the rule’s lateral axis | by computed value type | per grammar | the specified value
row-rule-lateral-inset-start | <length-percentage> | auto | auto | multi-column containers, flex containers, grid containers, table and table-row-group containers | no | refer to the rule containing rectangle’s size in the rule’s lateral axis | by computed value type | per grammar | the specified value
row-rule-length | <length-percentage> | auto | auto | multi-column containers, flex containers, grid containers, table and table-row-group containers | no | refer to the rule containing rectangle’s size in the rule’s longitudinal axis | by computed value type | per grammar | the specified value
row-rule-longitudinal-edge-inset | <'row-rule-longitudinal-edge-inset-start'> <'row-rule-longitudinal-edge-inset-end'>? | see individual properties | see individual properties | see individual properties | see individual properties | see individual properties | per grammar | see individual properties
row-rule-longitudinal-edge-inset-end | <length-percentage> | auto | 0 | multi-column containers, flex containers, grid containers, table and table-row-group containers | no | refer to the rule containing rectangle’s size in the rule’s longitudinal axis | by computed value type | per grammar | the specified value
row-rule-longitudinal-edge-inset-start | <length-percentage> | auto | 0 | multi-column containers, flex containers, grid containers, table and table-row-group containers | no | refer to the rule containing rectangle’s size in the rule’s longitudinal axis | by computed value type | per grammar | the specified value
row-rule-longitudinal-inset | <'row-rule-longitudinal-inset-start'> <'row-rule-longitudinal-inset-end'>? | see individual properties | see individual properties | see individual properties | see individual properties | see individual properties | per grammar | see individual properties
row-rule-longitudinal-inset-end | <length-percentage> | auto | 0 | multi-column containers, flex containers, grid containers, table and table-row-group containers | no | refer to the rule containing rectangle’s size in the rule’s longitudinal axis | by computed value type | per grammar | the specified value
row-rule-longitudinal-inset-start | <length-percentage> | auto | 0 | multi-column containers, flex containers, grid containers, table and table-row-group containers | no | refer to the rule containing rectangle’s size in the rule’s longitudinal axis | by computed value type | per grammar | the specified value
row-rule-style | <line-style> | none | multi-column containers, flex containers, grid containers, table and table-row-group containers | no | N/A | discrete | per grammar | specified keyword
row-rule-width | <line-width> | <percentage> | auto | medium | multi-column containers, flex containers, grid containers, table and table-row-group containers | no | refer to the rule containing rectangle’s size in the rule’s lateral axis | by computed value type | per grammar | absolute length if the specified value is <line-width>; 0px if the column rule style is none or hidden. Otherwise, the specified value.

## Issues Index

lots of new possible shorthands... we now have many properties (and shorthands) with a column-rule and row-rule prefix. Should we add shorthands for some of those with a rule prefix to specify both axes, like so: 'rule-foo: <row-rule-foo> <column-rule-foo>?'. As usual, we have to be careful with the separator though, to make it forward-compatible with any changes we might want to make... ↵
Are there use cases for other box-related edge attachment points? e.g. 'padding | padding-center | padding-over | border...' ↵
perhaps make all a separate keyword? like so: [segment | [[start | end | short | long] all?] ] allow-overlap? ↵
TODO: add definition list and algorithm here... ↵
is it useful to be able to create a rule extent for the intersection or union between two tracks, like so: It’s pretty easy to implement, fwiw... (I accidently implemented short/long like that before I realized it was inconsistent with how they work elsewhere). I think it’s a case that is unique to a masonry axis though, at least currently... ↵
sort out if non-collapsed column-groups that only contain collapsed columns should generate rules, ditto row-groups/rows ↵
this proposal makes the assumption that the related proposal that row-gap should apply to multi-column containers is also adopted (issue #6746). ↵
#lateral-axis Referenced in:

- 3.1. The column-rule-width and row-rule-width Properties (2)
- 3.2. The column-rule-length and row-rule-length Properties
- 3.3. The Rule Lateral Inset Properties
- 7. The Rule Containing Rectangle

#longitudinal-axis Referenced in:

- 3.2. The column-rule-length and row-rule-length Properties
- 3.6. The Rule Longitudinal Inset Properties
- 3.8. The Rule Longitudinal Edge Inset Properties (2)
- 5.1. The column-rule-align and row-rule-align Properties
- 5.2. The column-rule-edge-align and row-rule-edge-align Properties
- 6.1. The column-rule-extent and row-rule-extent Properties
- 7. The Rule Containing Rectangle

#rule-length Referenced in:

- 3.2. The column-rule-length and row-rule-length Properties

#propdef-column-rule-image-source Referenced in:

- 2.1. The column-rule-image-source and row-rule-image-source Properties
- 2.4. The column-rule-image and row-rule-image Shorthands

#propdef-row-rule-image-source Referenced in:

- 2.1. The column-rule-image-source and row-rule-image-source Properties

#propdef-column-rule-image-slice Referenced in:

- 2.2. The column-rule-image-slice and row-rule-image-slice Properties (2) (3)
- 2.4. The column-rule-image and row-rule-image Shorthands

#propdef-row-rule-image-slice Referenced in:

- 2.2. The column-rule-image-slice and row-rule-image-slice Properties

#propdef-column-rule-image-repeat Referenced in:

- 2.3. The column-rule-image-repeat and row-rule-image-repeat Properties
- 2.4. The column-rule-image and row-rule-image Shorthands

#propdef-row-rule-image-repeat Referenced in:

- 2.3. The column-rule-image-repeat and row-rule-image-repeat Properties

#propdef-column-rule-image Referenced in:

- 2.4. The column-rule-image and row-rule-image Shorthands

#propdef-row-rule-image Referenced in:

- 2.4. The column-rule-image and row-rule-image Shorthands

#propdef-row-rule-width Referenced in:

- 3.1. The column-rule-width and row-rule-width Properties
- 4.2. The row-rule Shorthand

#propdef-column-rule-length Referenced in:

- 3.2. The column-rule-length and row-rule-length Properties
- 7. The Rule Containing Rectangle (2)

#propdef-row-rule-length Referenced in:

- 3.2. The column-rule-length and row-rule-length Properties

#propdef-column-rule-lateral-inset-start Referenced in:

- 3.5. The column-rule-lateral-inset and row-rule-lateral-inset Shorthands

#propdef-column-rule-lateral-inset-end Referenced in:

- 3.5. The column-rule-lateral-inset and row-rule-lateral-inset Shorthands

#propdef-row-rule-lateral-inset-start Referenced in:

- 3.5. The column-rule-lateral-inset and row-rule-lateral-inset Shorthands

#propdef-row-rule-lateral-inset-end Referenced in:

- 3.5. The column-rule-lateral-inset and row-rule-lateral-inset Shorthands

#propdef-column-rule-lateral-inset Referenced in:

- 3.5. The column-rule-lateral-inset and row-rule-lateral-inset Shorthands

#propdef-row-rule-lateral-inset Referenced in:

- 3.5. The column-rule-lateral-inset and row-rule-lateral-inset Shorthands

#propdef-column-rule-longitudinal-inset-start Referenced in:

- 3.7. The column-rule-longitudinal-inset and row-rule-longitudinal-inset Shorthands

#propdef-column-rule-longitudinal-inset-end Referenced in:

- 3.7. The column-rule-longitudinal-inset and row-rule-longitudinal-inset Shorthands
- 7. The Rule Containing Rectangle

#propdef-row-rule-longitudinal-inset-start Referenced in:

- 3.7. The column-rule-longitudinal-inset and row-rule-longitudinal-inset Shorthands

#propdef-row-rule-longitudinal-inset-end Referenced in:

- 3.7. The column-rule-longitudinal-inset and row-rule-longitudinal-inset Shorthands

#propdef-column-rule-longitudinal-inset Referenced in:

- 3.7. The column-rule-longitudinal-inset and row-rule-longitudinal-inset Shorthands

#propdef-row-rule-longitudinal-inset Referenced in:

- 3.7. The column-rule-longitudinal-inset and row-rule-longitudinal-inset Shorthands

#propdef-column-rule-longitudinal-edge-inset-start Referenced in:

- 3.9. The column-rule-longitudinal-edge-inset and row-rule-longitudinal-edge-inset Shorthands

#propdef-column-rule-longitudinal-edge-inset-end Referenced in:

- 3.9. The column-rule-longitudinal-edge-inset and row-rule-longitudinal-edge-inset Shorthands

#propdef-row-rule-longitudinal-edge-inset-start Referenced in:

- 3.9. The column-rule-longitudinal-edge-inset and row-rule-longitudinal-edge-inset Shorthands

#propdef-row-rule-longitudinal-edge-inset-end Referenced in:

- 3.9. The column-rule-longitudinal-edge-inset and row-rule-longitudinal-edge-inset Shorthands

#propdef-column-rule-longitudinal-edge-inset Referenced in:

- 3.9. The column-rule-longitudinal-edge-inset and row-rule-longitudinal-edge-inset Shorthands

#propdef-row-rule-longitudinal-edge-inset Referenced in:

- 3.9. The column-rule-longitudinal-edge-inset and row-rule-longitudinal-edge-inset Shorthands

#propdef-row-rule-style Referenced in:

- 4.1. The row-rule-style and row-rule-color Properties
- 4.2. The row-rule Shorthand

#propdef-row-rule-color Referenced in:

- 4.1. The row-rule-style and row-rule-color Properties
- 4.2. The row-rule Shorthand

#propdef-row-rule Referenced in:

- 4.2. The row-rule Shorthand

#propdef-column-rule-align Referenced in:

- 5.1. The column-rule-align and row-rule-align Properties
- 7. The Rule Containing Rectangle (2)

#propdef-row-rule-align Referenced in:

- 5.1. The column-rule-align and row-rule-align Properties (2)
- 6.1.1.1. Subgrid

#propdef-column-rule-edge-align Referenced in:

- 5.2. The column-rule-edge-align and row-rule-edge-align Properties
- 6.1.1.2. Masonry

#propdef-row-rule-edge-align Referenced in:

- 5.2. The column-rule-edge-align and row-rule-edge-align Properties

#propdef-column-rule-extent Referenced in:

- 6.1. The column-rule-extent and row-rule-extent Properties
- 6.1.1.2. Masonry
- 6.1.2. Flex Containers (2)

#propdef-row-rule-extent Referenced in:

- 6.1. The column-rule-extent and row-rule-extent Properties
- 6.1.2. Flex Containers (2) (3) (4) (5)

#segment Referenced in:

- 6.1.5. Multi-Column Containers

#extent-size Referenced in:

- 6.1.1. Grid Containers (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12)
- 6.1.2. Flex Containers (2) (3)
- 7. The Rule Containing Rectangle

#valdef-row-rule-extent-short Referenced in:

- 6.1.2. Flex Containers (2)

#valdef-row-rule-extent-long Referenced in:

- 6.1.2. Flex Containers

#next-grid-cell-span Referenced in:

- 6.1.1. Grid Containers (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12)

#next-flex-line-item Referenced in:

- 6.1.2. Flex Containers (2) (3) (4) (5) (6) (7) (8)

#rule-containing-rectangle① Referenced in:

- 2.2. The column-rule-image-slice and row-rule-image-slice Properties
- 3.1. The column-rule-width and row-rule-width Properties (2)
- 3.2. The column-rule-length and row-rule-length Properties
- 3.3. The Rule Lateral Inset Properties (2)
- 3.4. Resolving a rule’s position and size (2)
- 3.6. The Rule Longitudinal Inset Properties (2) (3)
- 3.8. The Rule Longitudinal Edge Inset Properties
- 5.1. The column-rule-align and row-rule-align Properties
- 5.2. The column-rule-edge-align and row-rule-edge-align Properties
- 7. The Rule Containing Rectangle (2) (3) (4) (5)