The Future of CSS
The Future of CSS
...or at least, some of it.
- Images!
- Lists!
- Flexbox Layout!
- Grid Layout!
- Values!
- Selectors!
- Maybe more?
- Q&A
Image Values
Defines several useful image-related features.
Should enter Last Call next week, and CR by the end of the year!
Gradients have changed over time...
- Linear gradients now use bearing angles (0deg is N, 90deg is E)
- Linear gradient keywords are now "
to <side-or-corner>"
- Corner-to-corner gradients are now "magic".
- Radial gradients can be explicitly sized.
Use an element as an image!
The image() function
Basically a souped-up url()
background: image("foo.webp", "foo.svg", "foo.png", blue);
background: image("arrow.png" ltr);
background: image(rgba(0,0,255,.2)), url(foo.jpg);
A few other bits
image-resolution- Specify the resolution of the image, so you can use high-res images (for printing) that are sized properly.
image-orientation- Rotate an image by 90deg increments. This affects layout, unlike
rotate() transforms.
object-fit, object-position- Size and position an image within its content box.
Lists!
Revival of an old 2003 spec
- Defines the
::marker pseudo-element
- Lets you directly style/position/etc the marker
- Defines 100+ new list styles
- Lets authors define their own list style
Defining your own list-style
@counter-style leaves {
type: repeating;
glyphs: url(leaf1.jpg) url(leaf2.jpg) url(leaf3.jpg);
}
@counter-style binary {
type: numeric;
glyphs: "0" "1";
}
Defining your own list-style
@counter-style dice {
type: additive;
additive-glyphs: 6 ’⚅‘, 5 ’⚄‘, 4 ’⚃‘, 3 ’⚂‘, 2 ’⚁‘, 1 ’⚀‘;
suffix: ’‘;
}
⚀ One
⚁ Two
⚂ Three
...
⚅⚄ Eleven
⚅⚅ Twelve
⚅⚅⚀ Thirteen
Flexbox!
Basically, display:block for applications.
Dumps much of the text-related complication in favor of simpler, more useful abilities.
Is nearly done being rewritten right now, and is currently being re-implemented in Chrome (other browsers should follow shortly).
Thousands of household uses!
Combining an input and a button
<div style="display: flexbox;">
<input style="width: flex(); display: block;">
<button>foo</button>
</div>
Thousands of household uses!
Horizontal navigation bar
<style>
ul { display: flexbox; }
li { width: flex(); }
</style>
<ul>
<li><a>Products</a></li>
...
<li><a>Training</a></li>
</ul>
Thousands of household uses!
Accordions
<div class=accordion>
<h1>First section</h1>
<section>Cool stuff to show in this section</section>
<h1>Second section</h1>
<section>More cool stuff for the second section</section>
...
</div>
<style>
.accordion {
display: flexbox;
flex-flow: column;
flex-pack: start;
}
.accordion > section {
height: 0;
overflow: hidden;
}
.accordion > section.active {
height: flex(1);
}
<style>
Grid Alignment!
Finally, a layout system designed for pages.
Slice the page into cells, and position elements into those cells.
No extraneous markup, no source-order dependence, fully flexible.
Grid Alignment!
grid-template: "a b"
"c b"
"d d"
"e e";
Grid Alignment!
grid-template: "a d"
"b d"
"c e";
Values & Units
http://dev.w3.org/csswg/css3-values/
This spec defines all the basic value types that CSS uses across its specs
Also defines the syntax used in property descriptions, if you ever wondered what the hell "&&" meant in a spec.
Some useful new units
rem is the em from the root element
ex is relative to the font's x-height, similar to the em
ch is the width of the "0" (an 'average character')
vw, vh units are relative to the size of the window
The calc() function
Lets you do math in CSS, combining things that are comparable
calc(50% + 20px)
calc(100% / 7)
The attr(), cycle() functions
attr() lets you pull values from attributes on the element
Useful for implementing the UA stylesheet, or for styling based on data-* attributes
width: attr(data-size as px, 100px);
cycle() takes several values, and "cycles" between them with each nested use
em { font-style: cycle(italic, normal); }ul { list-style-type: cycle(circle, square, dot); }
Column pseudos
In HTML, the column of a cell is indicated implicitly, rather than directlly through nesting. This makes it impossible to style an element based on its column, except for the 4 properties that the spec allows <col> to have.
td:col(col.foo) selects the cells within the column that matches "col.foo"
td:nth-col(n) and td:nth-last-col(n) work in the expected way
Link pseudos
:any-link is :link done right - matches both visited and unvisited links
:local-link matches links to elsewhere in the same page
:local-link(n) matches based on subsets of the path - :local-link(0) looks only at the domain, :local-link(1) looks at the domain and the first segment of the path, etc.
Time pseudos
Only useful for presentation formats that are time-based, like karaoke captions in an HTML <video> or a screen reader
:current matches the current active element
:past and :future matches elements that have already been passed, or haven't been hit yet, respectively
video::cue(:past) { color: red; }
video::cue(:future) { color: white; }
/* Bouncing ball left as an exercise for the reader */
The Reference Combinator
Lets you follow IDREF attributes in the selector, like <label for=foo>
label:hover /for/ input { outline: thick dotted red; }
CSS Variables!
Variables! In CSS! OMG!
A common request for literally over a decade.
Why so long?
Previously, discussion was paralyzed by indecision and argument.
Now we have very rough agreement on the solution, and are starting experimental implementations.
Var Example
html {
data-header-color: #006;
data-main-color: #06c;
data-accent-color: #c06;
}
a { color: data(main-color); }
a:visited { color: data(accent-color); }
h1 {
color: data(header-color);
background: linear-gradient(data(main-color), transparent 25%);
}
CSS Nesting!
Stylesheets often have tons of repetition in the selectors.
"#main > header > h1", "#main > header > h1 > a",
"#main > header > h1 > a:visited", etc.
Verbose, hard to read, prone to hard-to-see errors
Old and Busted
#main > header > h1 {
font-size: 2em;
background: blue;
color: white;
}
#main > header > h1 > a {
color: #ddf;
}
#main > header > h1 > a:visited {
color: #fdf;
}
Nesting Example
#main > header > h1 {
font-size: 2em;
background: blue;
color: white;
& > a {
color: #ddf;
&:visited {
color: #fdf;
}
}
}
Just syntax sugar for the long-form stuff.
Again, CSS preprocessors led the way.
Shorter stylesheets, better organization mean faster app development.
Explicitly indicates scoping opportunities, which might be useful for browser
perf