CSS Variables in Firefox 31 – new syntax

http://jan.rs/blog/css-variables-in-firefox-31-new-syntax/

by reimersjan • 12 years ago

77 53 12 years ago

jan.rs

bshimmin5• 12 years ago

That new syntax is astonishingly ugly and bizarre.

I'm sure it'll be a real joy to use that for anyone who's been using Sass or Less (and who doesn't, these days...).

galvin• 12 years ago

Yeah, obviously they need to avoid conflicts but surely they could have found a single character to use as a prefix instead of "--", like "$" or "@".

The "var()" function is just.. redundant. Or maybe I'm missing something?

colinramsay• 12 years ago

Here's the discussion where they changed from "var-" to "--":

http://lists.w3.org/Archives/Public/www-style/2014Mar/0261.h...

And later on the justification for not using $ or @:

http://lists.w3.org/Archives/Public/www-style/2014Mar/0400.h...

There's also the issue that this needs to be backwards compatible with parsers that don't support the syntax, and apparently because the variables cascade that makes it harder still. I agree it's ugly though.

ibotty• 12 years ago

`--` is a comment in many languages (sql, haskell, ..).

bshimmin5• 12 years ago

And of course it's a decrement operator in many others! It doesn't seem at all intuitive as a sigil to use for this purpose.

est• 12 years ago

I'd rather use reactjs to style everything than this.

joesb• 12 years ago

That doesn't make sense.

peaton2• 12 years ago

So in this article, the author says this is not supported on chrome. But in this stack question [1], chrome is clearly using it. Is the only difference the author is discussing that now firefox uses/supports "--" instead of "var-"?

[1] http://stackoverflow.com/questions/18466569/enable-experimen...

artursapek• 12 years ago

It was removed from Chrome in February. https://groups.google.com/a/chromium.org/forum/#!topic/blink...

peterjmag• 12 years ago

CSS variables were recently removed from Chrome: http://stackoverflow.com/a/23518831/349353

peaton2• 12 years ago

I see, thanks for pointing that out.

rubiquity2• 12 years ago

Woah. CSS variables look like compiler flags. There goes the W3C reinventing the wheel when Sass, Less and others have already laid out how to assign variables just fine for years.

gavinpc• 12 years ago

As other posts have stated, CSS variables are not the same thing as preprocessor variables. Specifically, they cascade.

A preprocessor cannot possibly implement CSS variables with cascading because it the value is resolved against a live context.

In other words, you can actually change the variable at runtime with rules that target different selectors.

As such, the "variables" are in fact functions.

rubiquity2• 12 years ago

Thanks for the break down. I'm not seeing the benefit of variables cascading, though.

arxpoetica• 12 years ago

Can anyone think of a use case for this beyond what a precompiler (Sass, Less, Stylus) can do?

bshimmin5• 12 years ago

I think the idea is you use this rather than a precompiler.

webXL• 12 years ago

Changing bootstrap theme colors on the fly would be one reason to use this, even though you might be compiling bootstrap on each build.

silverbax88• 12 years ago

Because precompilers are sort of a disruption of the point of CSS to begin with. I know, I know, a lot of people use them, but using style sheets that require compilation pretty much defeats the purpose of separation.

DougWebb• 12 years ago

Yes and no. The browser has to parse the CSS, and it's most likely building an abstract symbol tree. So in a sense CSS is compiled too, it just happens in the browser so web developers don't have to be aware of it.

Do you remember the type attribute?

    <style type="text/css">...</style>

That was originally put there so we could have different types of stylesheet languages, instead of everyone having to use CSS all of the time. Maybe browsers should incorporate the most popular LESS and SASS projects so that they can support type="text/less" and type="text/sass" too. Some workaround will be needed for old browsers (a javascript shim that retrieves server-compiled css) during the transition period, but eventually we'd end up with being able to use LESS, SASS, and CSS where needed, interchangably.

epidemian• 12 years ago

I couldn't think of a very good example, but here's something: http://codepen.io/anon/pen/vuyAI

The CSS use a couple of custom properties that define the foreground and background colors. Then, some elements redefine those custom properties (through CSS or JS) and that in turn makes all their children inherit the new custom properties' values and change their styles. This makes the rules that use the custom properties very general, and avoids the need to write more specific rules for the alternative colors. I hope this makes sense :)

I don't think this is possible to do with CSS preprocessors.

lambda2• 12 years ago

For one, it means that you don't need to have a precompiler step in the development process. You can more easily edit the value inline in your browser's developer tools. You can more easily put together simple static sites.

Another is that you can use it in conjunction with calc(), which you can't do in a preprocessor. Take a look at some example use cases for calc, which can't be done in a preprocessor: http://css-tricks.com/a-couple-of-use-cases-for-calc/ Now instead of just using constant values in those, you can use variables. This can be even more powerful for responsive designs, because you can set the variable to different values based on a media query.

pornel2• 12 years ago

These are not like SASS variables. I think calling this variables is causing unnecessary confusion.

This feature adds custom properties. CSS had custom vendor properties like `-webkit-foo`, and now you can have your own properties with vendor == "", so it's `--foo`.

bshimmin5• 12 years ago

I think this is just a problem of nomenclature. In CSS, a statement such as

  font-color : red;

comprises a "property" (left) and a "value" (right). The draft W3C proposal allows you to specify a "custom property" and assign a value to it, thus:

  --header-bg-colour : #ff5533;

You can then reference this elsewhere by saying:

  header { background-color : var(--header-bg-colour); }

Isn't that just how you use a variable (written as $header-bg-colour) in Sass?

pornel2• 12 years ago

The similarity is only superficial. SASS variables are lexically scoped. CSS properties are cascading.

sergiotapia• 12 years ago

Does the W3C not have internet access to learn about existing solutions and least try to emulate the good parts?

LESS and SASS are much better about variables, what the heck were they thinking?

    background-color: var(--best-gray-ever);

Not exactly intuitive or easy to parse at a glance.

ep103• 12 years ago

The w3c has been failing at their job for some 15 years now. Enabling drm in html5 and giving the mpaa a seat on their board should have been the last straw. Ignore them, and start looking to WhatWg

lucian1900• 12 years ago

Most of the members of whatwg also like the DRM bits.

paulrouget• 12 years ago

what the heck were they thinking?

I don't know, maybe about how to design a spec that is compatible with past and future CSS parsers and features?

People think it's so simple to come up with a new feature for CSS/HTML/JS, when actually, they have no idea how difficult it is.

They're smarter than that: http://www.xanthir.com/blog/b4KT0

aikah• 12 years ago

Sure,but when the spec is bad at first place,no new feature can be good.So hell yeah ...

what the heck were they thinking?

...At first place when they wrote CSS.

CSS is a disaster,and one of the worst spec ever written in my book.

People think it's so simple to come up with a new feature for CSS/HTML/JS, when actually, they have no idea how difficult it is.

Aside from HTML,CSS and JS are "defacto" standards since vendors werent able to agree on a better spec when they should have. only developpers can fix these with tools they build.Devs cant rely on these technologies on their own.That's why they have CSS and JS preprocessors.Because while it's crap at the end of the day devs need to build on top of that crap.

ihuman• 12 years ago

Does anyone know if the var() function only work with the variables? For example, can I do something like:

  background-color: var(color);?

ahoge• 12 years ago

Doesn't work.

http://jsfiddle.net/QEJw9/

bouncingsoul• 12 years ago

In case you didn't know, there's already a special version of the `inherit` keyword for using the color value in other properties:

    background-color: currentColor;

Fully supported in all modern browsers. http://devdocs.io/css/color_value#currentColor_keyword

Thiz• 12 years ago

Ugly as hell. Go back to the drawing board.

jasonpriestley2• 12 years ago

Writing your styles in javascript is a better option. You get variables, as well as functions and modules (e.g. with browserify), all with sane syntax and semantics (no "cascade").

Preprocessors are an inferior solution, limited by the semantics of CSS and leading, by the pervasive use of macros, to needlessly large CSS file sizes.

VMG• 12 years ago

What's the best solution for writing styles exclusively in JS and avoiding CSS completely?

jasonpriestley2• 12 years ago

My practice is to build the DOM programmatically with jQuery, and add styles to the elements directly

   $("<div>")
     .css({width: 100, height: 20, color: 'red'})
     .appendTo(container);

Then, since these are just values in normal javascript code, you can refactor as normal. Pull commonly used patterns out into functions (e.g. `importantText(16, "size 16 important text goes here")`).

Most styles in the applications I write tend to be inextricably linked to the layout and function of a component (e.g., tabs should be next to each other); in the rare case that a style needs to be customized in different locations or at different times, it becomes a parameter (e.g. `confirmDialog(textStyle, message, onOk, onCancel)`)

No extra tools are needed, beyond jQuery (building up the DOM without jQuery or something like it is awful).

talmand3• 12 years ago

I've made this argument before, using JS exclusively for styling does not let you avoid CSS. It lets you avoid certain aspects of CSS that may, or may not, be helpful.

kuschku• 12 years ago

And does your styling work in a webbrowser where JS is disabled?

peter_l_downs• 12 years ago

Not trolling, I really don't understand: why would you disable JS when browsing the web?

chenglou• 12 years ago

https://github.com/chenglou/RCSS

nfriedly• 12 years ago

I like it. The syntax actually feels more css-like to me than what most preprocessors use. But never mind the syntax, the killer feature us the cascading - that's what sells me on this vs SASS/LESS/etc. (And, having it native is also nice - this way I can just dump something on Github Pages and skip the compilation step.)

talmand3• 12 years ago

Can you suggest a use-case where the cascading variables is a helpful thing?

AshleysBrain• 12 years ago

Why do you have to use var(--name) when the parser already knows it's a variable from the -- prefix? Surely property: --name; is nicer than property: var(--name); ?

CSS Variables in Firefox 31 – new syntax

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