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<h1>CSS Shapes Module Level 2</h1>
<pre class='metadata'>
Status: ED
Shortname: css-shapes
Level: 2
Group: csswg
TR: http://www.w3.org/TR/css-shapes-2/
ED: http://dev.w3.org/csswg/css-shapes-2/
Editor: Alan Stearns, Adobe Systems, Inc., stearns@adobe.com
!Issues list: <a href="https://www.w3.org/Bugs/Public/buglist.cgi?query_format=advanced&product=CSS&component=Shapes&resolution=---&cmdtype=doit">In Bugzilla</a>
Abstract: This draft contains the features of CSS relating to wrapping content around and inside shapes. It (implicitly for now) includes and extends the functionality of CSS Shapes Level 1 [[CSS-SHAPES]]. The main points of extension compared to level 1 include additional ways of defining shapes, defining an exclusion area using a shape, and restricting an element's content area using a shape.
Link Defaults: css21 (property) margin, css-display-3 (value) table
</pre>
<style type="text/css">
.singleImgExample {
display: block;
margin: auto;
}
.example-table {
table-layout: fixed;
width: 100%;
}
.example-table tr td img {
width: 90%;
}
</style>
<h2 id="intro">
Introduction</h2>
<em>This section is not normative.</em>
Level 1 of this specification
defined properties to control
the geometry of an element's
<span>float area</span>.
This level defines how shapes apply to exclusions.
It also includes a 'shape-inside' property
for applying a shape
to an element's content area.
And finally it defines new ways
of specifying shapes for all
of these applications.
<h2 id="terminology">
Terminology</h2>
<dfn>Exclusion area</dfn>
The area used for excluding
inline flow content
around an exclusion box.
The <span>exclusion area</span>
is equivalent to the
<a href="http://www.w3.org/TR/CSS2/box.html#box-dimensions">border box</a>
for an exclusion box.
This specification's 'shape-outside' property
can be used to define arbitrary,
non-rectangular <span>exclusion areas</span>.
The 'shape-inside' property also defines
an <span>exclusion area</span>,
but in this case it is the area outside the shape
that inline content avoids.
<dfn>Float area</dfn>
The area used for wrapping content
around a float element.
By default,
the float area is
the float element's
<a href="http://www.w3.org/TR/CSS2/box.html#box-dimensions">margin box</a>.
This specification's 'shape-outside' property
can be used to define arbitrary,
non-rectangular float areas.
<dfn>Content area</dfn>
The <a href="http://www.w3.org/TR/CSS2/box.html#box-dimensions">content area</a>
is normally used for layout of the inline flow content of a box.
<div class="issue-marker" data-bug_id="15089" data-bug_status="NEW">
<a href="https://www.w3.org/Bugs/Public/show_bug.cgi?id=15089">Issue-15089</a>
<div class="issue-details">
<p class="short-desc">shrink-to-fit circle / shape</p>
</div>
</div>
<h2 id="shapes">
Shapes</h2>
Shapes define arbitrary geometric contours
around which inline content flows.
The shape-outside property defines
the <span>float area</span> for a float,
and the exclusion area for an exclusion.
<h3 id="basic-shapes-from-svg-syntax">
Basic Shapes</h3>
Add the final
<a href="http://www.w3.org/TR/css-shapes/#basic-shapes-from-svg-syntax">level 1</a>
section with a possible addition of path() and a rejiggered rectangle().
<div class="issue-marker wrapper">
<div class="issue-marker" data-bug_id="16448" data-bug_status="ASSIGNED">
<a href="https://www.w3.org/Bugs/Public/show_bug.cgi?id=16448">Issue-16448</a>
<div class="issue-details">
<p class="short-desc">Should we revisit the decision to not allow SVG path syntax in the shape-inside, shape-outside properties</p>
</div>
</div>
</div>
<h3 id='referencing-svg-shapes'>
Referencing SVG shapes</h4>
An SVG shape can be referenced using the <code>url()</code> syntax.
The shape can be any
of the <a href="http://www.w3.org/TR/SVG/shapes.html">SVG basic shapes</a>
or a <a href="http://www.w3.org/TR/SVG/paths.html">path element</a>.
<div class="example">
<div style="float:right">
<img alt="results of referencing SVG shapes" src="images/svg-shape-reference.png">
</div>
<code class="html"><pre>
<style>
div {
height: 400px;
width: 400px;
}
.in-a-circle {
shape-outside: url(#circle_shape);
}
.in-a-path {
shape-outside: url(#path-shape);
}
</style>
<svg ...>
<circle id="circle_shape" cx="50%" cy="50%" r="50%" />
<path id="path-shape" d="M 100 100 L 300 100 L 200 300 z" />
</svg>
<div class="around-a-circle">...</div>
<div class="around-a-path">...</div>
</pre></code>
</div>
<h3 id="shapes-from-image">
Shapes from Image</h3>
Add the final
<a href="http://www.w3.org/TR/css-shapes/#shapes-from-image">level 1</a>
section.
Issue: One <a href="https://www.w3.org/Bugs/Public/show_bug.cgi?id=16716">suggestion</a>
is to define a shape based on an element's rendered content.
This could have security implications.
Issue: Another <a href="http://lists.w3.org/Archives/Public/www-style/2014Mar/0120.html">s
7440
uggestion</a>
is to add something to an image() function
that determines the relevant pixels to use
(both for defining a shape and for display).
<h3 id="declaring-shapes">
Declaring Shapes</h3>
A shape can be declared with
the 'shape-outside' property,
with possible modifications
from the 'shape-margin' property.
The shape defined by
the 'shape-outside'
and 'shape-margin' properties
changes the geometry
of a float element's
<span>float area</span>
and an exclusion element's
<span>exclusion area</span>.
A shape can be declared with
the 'shape-inside' property,
with possible modifications
from the 'shape-padding' property.
The shape defined by
the 'shape-inside'
and 'shape-padding' properties
defines an <span>exclusion area</span>
that contributes
to the element's <span>wrapping context</span>.
The 'shape-inside' property applies
to all block-level elements.
<div class="example">
The red box illustrates
an exclusion element's content box,
which is unmodified and subject
to normal CSS positioning
(here absolute positioning).
<pre><code class="html">
<style type="text/css">
.exclusion {
wrap-flow: both;
position: absolute;
top: 25%;
left: 25%;
width: 50%;
height: 50%;
shape-outside: circle(50% at 50% 50%);
border: 1px solid red;
}
</style>
<div style=”position: relative;”>
<div class=”exclusion”></div>
Lorem ipsum dolor sit amet...
</div>
</code></pre>
<img class="singleImgExample"
src="images/shapes_CSS2.1_MBP.png"
alt="Example rendering of circle shape and box model."
style="max-width:40%"/>
</div>
<h4 id="shape-outside-property">
The 'shape-outside' Property</h4>
Add the final
<a href="http://www.w3.org/TR/css-shapes/#shape-outside-property">level 1</a>
section with the change that
shape-outside applies
to block-level elements
and has an effect
if the element
is an exclusion.
<h4 id="shape-inside-property">
The 'shape-inside' Property</h4>
The 'shape-inside' property adds
one or more exclusion areas
to the element's wrapping context.
This modifies the normal rectangular shape
of the content area
to a possibly non-rectangular wrapping area.
The exclusion areas
are defined by subtracting the shape
from the element's content area.
Any part of the shape outside
the element's content area
has no effect.
<pre class='propdef'>
Name: shape-inside
Value: auto | outside-shape | [ <<basic-shape>> || shape-box ] | <<image>>
Initial: auto
Applies To: block-level elements
Inherited: no
Computed Value: computed lengths for <<basic-shape>>, the absolute URI for <<uri>>, otherwise as specified</td>
Media: visual
Animatable: as specified for <<basic-shape>>, otherwise no
</pre>
The values of this property have the following meanings:
<dl>
<dt><dfn for=shape-inside>''auto''</dfn></dt>
<dd>
The shape is computed based on the content box of the element.
</dd>
</dl>
<dl>
<dt><dfn><basic-shape></dfn></dt>
<dd>
The shape is computed based
on the values of one of
''inset()'', ''circle()'', ''ellipse()'' or ''polygon()''.
</dd>
</dl>
<dl>
<dt><dfn><uri></dfn></dt>
<dd>
If the <uri> references an SVG shape element,
that element defines the shape.
Otherwise, if the <uri> references an image,
the shape is extracted and computed
based on the alpha channel
of the specified image.
If the <uri> does not reference
an SVG shape element or an image,
the effect is as if the value ''auto'' had been specified.
</dd>
</dl>
The 'shape-inside' property applies to floats.
The 'shape-inside' property may not apply on some elements
such as elements with a computed 'display' value of ''display/table''.
<div class='figure'>
<img alt="Content flowing with and without a shape-inside"
src="images/shape-inside-content.png"/>
<p class="caption">Effect of shape-inside on inline content.</p>
</div>
Overflow content avoids
the exclusion area(s) added
by 'shape-inside' and 'shape-padding'
(as well as any other exclusion areas
in the element's wrapping context).</p>
<div class='figure'>
<img alt="Overflow interacting with rounded rect"
style="display:inline-block;vertical-align:top"
src="images/rounded-rect-overflow.png"/>
<img alt="Overflow interacting with ellipse"
style="display:inline-block;vertical-align:top"
src="images/ellipse-overflow.png"/>
<p class="caption">
Overflow interacting with exclusion areas defined
by 'shape-inside' and 'shape-padding'.
</p>
</div>
When a shape-inside has a definite size
(no percentages used in the shape's definition)
an auto-sized element should use the shape
as a constraint in determining its maximum size.
<h4 id="shape-image-threshold-property">
The shape-image-threshold Property</h4>
Add the final
<a href="http://www.w3.org/TR/css-shapes/#shape-image-threshold-property">level 1</a>
section with the change that
it applies to both <span>shape-inside</span>
and <span>shape-outside</span>.
<h4 id="shape-image-source-type-property">
The shape-image-source-type Property</h4>
Should we add an alpha/luminance switch
to determine which values we use
from the shape-image source?
This could just be a keyword
on the shape-image-threshold property.
Whatever we go with should be compatible
with the alpha/luminance switch from mask sources.
<h4 id="shape-margin-property">
The 'shape-margin' property</h4>
Add the final
<a href="http://www.w3.org/TR/css-shapes/#shape-margin-property">level 1</a>
section with the change that it applies to exclusions.
<h4 id="shape-padding-property">
The 'shape-padding' Property</h4>
The 'shape-padding' property adds padding to a shape-inside.
This defines a new shape where every point
is the specified distance from the shape-inside.
This property takes on positive values only.
<pre class='propdef'>
Name: shape-padding
Value: <<length>>
Initial: none
Applies To: block-level elements
Inherited: no
Computed Value: the absolute length
Media: visual
Animatable: as <a href="http://www.w3.org/TR/css3-transitions/#animtype-lpcalc">length, percentage, or calc</a>
</pre>
<div class="example">
<p>A 'shape-padding' creating an offset
from a circlular shape-inside.
The light blue rectangles represent
inline content affected
by the shape created
by the padding.</p>
<img src="images/shape-padding.png"
alt="Example of a shape-padding offset"/>
</div>
Note: The 'shape-padding' property
only affects layout of content
inside the element it applies to
while the 'shape-margin' property
only affects layout of content
outside the element.