Shortname: css-sizing Level: 3 Status: ED Work Status: Exploring Group: csswg ED: http://dev.w3.org/csswg/css-sizing TR: http://www.w3.org/TR/css3-sizing/ Editor: Tab Atkins, Google, http://xanthir.com/contact/ Editor: Elika J. Etemad / fantasai, Invited Expert, http://fantasai.inkedblade.net/contact/ !Issue Tracking: W3C Bugzilla Previous version: http://www.w3.org/TR/2012/WD-css3-sizing-20120927/ Abstract: This module extends the CSS sizing properties with keywords that represent content-based "intrinsic" sizes and context-based "extrinsic" sizes, allowing CSS to more easily describe boxes that fit their content or fit into a particular layout context. Link Defaults: css21 (property) min-width/min-height/max-width/max-height, css21 (dfn) initial containing block/block container box Ignored Terms: block-level box
url: http://dev.w3.org/csswg/css2/visuren.html#x3; type: dfn; text: containing block
This section is not normative.
CSS layout has several different concepts of automatic sizing that are used in various layout calculations. This section defines some more precise terminology to help connect the layout behaviors of this spec to the calculations used in other modules, and some new keywords for the 'width' and 'height' properties to allow authors to assign elements the dimensions resulting from these size calculations.
This module extends the 'width', 'height', 'min-width', 'min-height', 'max-width', 'max-height', and 'column-width' features defined in [[!CSS21]] chapter 10 and in [[!CSS3COL]]
This specification follows the CSS property definition conventions from [[!CSS21]]. Value types not defined in this specification are defined in CSS Level 2 Revision 1 [[!CSS21]]. Other CSS modules may expand the definitions of these value types: for example [[CSS3COLOR]], when combined with this module, expands the definition of the <color> value type as used in this specification.
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.
Note: This is the formula used to calculate the ''width/auto'' widths of non-replaced blocks in normal flow in CSS2.1§10.3.3.
min(max-content size, max(min-content size, fill-available size)). Otherwise, equal to the max-content size in that axis. Note: This is called the “shrink-to-fit” width in CSS2.1§10.3.5 and CSS Multi-column Layout § 3.4.
Name: width, min-width, max-width, height, min-height, max-height New values: fill | max-content | min-content | fit-content
There are four types of automatically-determined sizes in CSS (which are represented in the width and height properties by the keywords defined above):
Does this value work? Is it needed? Feedback from dbaron
Right now all of these except ''width/fill'' mean the same thing for block-sizes. This may or may not be ideal.
If the inline-size is ''width/auto'', we could have min-content block-size imply a max-content inline-size, and vice versa.
Note that percentages resolved against the intrinsic sizes (''width/max-content'', ''width/min-content'', ''width/fit-content'', ''width/repudiate-floats'') will compute to ''width/auto'', as defined by CSS 2.1. [[!CSS21]]
Name: min-width, min-height New values: contain-floats
Name: column-width New values: fill | max-content | min-content | fit-content
When used as values for 'column-width', the new keywords specify the optimal column width:
min(max-content inline size, max(min-content inline size, fill-available inline size)).
Intrinsic sizing determines sizes based on the contents of an element, without regard for its context.
For replaced elements, the min-content size and max-content size are equivalent and correspond to the appropriate dimension of the concrete object size returned by the default sizing algorithm [[!CSS3-IMAGES]] of the element, calculated with an unconstrained specified size. The min-content contribution and max-content contribution in each axis is the element's specified outer size in that axis, if definite; otherwise, they are the min-content size, as specified above, plus the element's margin/border/padding in that axis, clamped by the element's min and max size properties in that axis.
The min-content inline size of an inline box is the length of the largest unbreakable sequence of inline content. The min-content inline-size contribution of an inline box is its min-content inline size, plus any inline-axis margin, border, and padding adjacent to that sequence.
The max-content inline size of an inline box is the length of the largest sequence of inline content on a single line when only forced line breaks are taken. The max-content inline-size contribution of an inline box is its max-content inline size, plus any inline-axis margin, border, and padding adjacent to that sequence.
The min-content block size, max-content block size, min-content block-size contribution, and max-content block-size contribution of an inline box are the distance from the head edge of the first line box to the foot edge of the last line box on which the inline appears.
The min-content inline size of a block container box is the largest min-content inline-size contribution of its in-flow or floated children.
The max-content inline size of a block container box is the inline-size of the box after layout, if all children are sized under a max-content constraint.
If the computed inline-size of a block-level box is ''width/min-content'', ''width/max-content'', or a definite size, its min-content inline-size contribution is that size plus any inline-axis margin, border, and padding. Otherwise, if the computed inline-size of the block is ''width/fit-content'', ''width/auto'', or ''width/fill'', its min-content inline-size contribution is its min-content inline size plus any inline-axis margin, border, and padding.
If the computed inline-size of a block-level box is ''width/min-content'', ''width/max-content'', or a definite size, its max-content inline-size contribution is that size plus any inline-axis margin, border, and padding. Otherwise, if the computed inline-size of the block is ''width/fit-content'', ''width/auto'', or ''width/fill'', its max-content inline-size contribution is its max-content inline size plus any inline-axis margin, border, and padding.
The min-content block size and max-content block size of a block container box is the content block-size as defined (for horizontal writing modes) in CSS2.1§10.6.3 and CSS2.1§17.5.3 for elements with ''height: auto'', and analogously for vertical writing modes.
The min-content block-size contribution and max-content block-size contribution of a block-level box is the block-size of the block after layout, plus any block-axis margin, border, and padding. Issue: Need to handle floats. See Greg's issue and dbaron's response.
The min-content inline size of a multi-column element with a computed 'column-width' not ''column-width/auto'' is the smaller of its 'column-width' and the largest min-content inline-size contribution of its contents.
The min-content inline size of a multi-column element with a computed 'column-width' of ''column-width/auto'' is the largest min-content inline-size contribution of its contents multiplied by its 'column-count' (treating ''column-count/auto'' as ''1'').
The max-content inline size of a multi-column element with unrestrained column heights and a computed 'column-count' not ''column-count/auto'' is its 'column-count' multiplied by the larger of its 'column-width' (treating ''column-width/auto'' as zero) and the largest min-content inline-size contribution of its contents.
Note that the contents of the multi-column element can still grow to be wider and shorter if the resulting column width is still smaller than the largest max-content inline-size contribution of its contents.
The max-content inline size of a multi-column element with unrestrained column heights and a computed 'column-count' of ''column-count/auto'' is its 'column-width' multiplied by the number of columns obtained by taking all allowed column breaks [[CSS3-BREAK]].
The max-content inline size of a multi-column element with restrained-height columns (i.e. a specified 'height' or 'max-height', or whichever properties map to the block size of the element) is the inline size that would exactly include all of its columns. It may be approximated by:
or by some more accurate method.
This approximation can result in some slack, but avoids overflow in the most common cases, where the balanced height of the columns above spanning elements are approximately equal.
In the common case of no column-spanning elements, this approximation collapses to simply doing a layout, and measuring the resulting columns.
Extrinsic sizing determines sizes based on the context of an element, without regard for its contents.
The inner fill-available inline size of a box is…
max(min-content inline size|0, min(max-content inline size|infinity, inline size|fill-available inline size))where the sizes are inner inline-sizes of the element establishing the box's containing block, and where the first value is used if it is definite and the second value otherwise.
…less the box's inline-axis margins (after any margin collapsing, and treating ''margin/auto'' margins as zero), borders, and padding.
The fill-available block size of a box is defined analogously, but in the other dimension.
This definition might end up skipping further up the ancestor chain than we'd like in some cases. Example. Maybe it should stop at each formatting root, or something similar?
Changes since the September 2012 Working Draft include:
Special thanks go to Aaron Gustafson, L. David Baron for their contributions to this module.