As CSS browser assist will increase, together with spectacular strides by the IE9 staff, increasingly more authors are plunging into CSS3. As they achieve this, they’re dealing with vendor prefixes—the -*- properties like -moz-border-radius, -webkit-animation, and so forth.
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Maybe inevitably, there’s been some grumbling about these prefixes. There have been calls to drop them, or to break down all of the vendor-specific prefixes right into a single prefix like -beta-. The first pushback is that no one actually desires to jot down the identical factor 4 or 5 occasions in a row simply to get, say, rounded corners on a component.
Whereas such grousing is comprehensible, it’s precisely the inverse of what must be taking place. We must reward distributors for utilizing prefixes, and certainly encourage them to proceed. Past that, I maintain that prefixes ought to turn out to be a central a part of the CSS standardization course of. I do that not for the love of repetition, however out of a want to see CSS evolve persistently. I consider that prefixes can really speed up the development and refinement of CSS.
Look again in horror#section2
To know why we now have vendor prefixes in any respect, it’s instructive to look again on the field mannequin, which just about killed CSS earlier than the flip of the millennium. Inconsistent field mannequin implementations created a disaster. To flee the hazard, we needed to construct a completely new habits on high of a markup function and invent a complete class of hacks.
For the younger whippersnappers within the viewers who missed all of the enjoyable, what occurred was this: Within the first spherical of browsers that supported CSS, Netscape applied the field mannequin discovered within the CSS specification. That meant that width and peak referred to the width and peak of the content material space. However Web Explorer applied the intuitive field mannequin, which meant that width and peak declared the size of the field’s outer border edge.
Whichever of the 2 you assume higher, the very fact remained that there have been two main browsers with massive consumer bases that had been utterly incompatible with one another. It was the late Nineteen Nineties, we had been preventing like hell to go away behind the morass of “this website greatest considered in…” badges, and right here we had a state of affairs the place a structure that labored high quality in a single browser may utterly crumble in one other.
Compounding the issue was that neither browser may change its habits to reflect the opposite. Assume for a second that the IE staff determined to alter their CSS assist to mirror the specification. To take action would imply that tens, even lots of of hundreds of websites that labored in IE would break—would fairly actually crumble, visually talking—within the “fastened” model. Whereas the requirements neighborhood would have applauded the transfer, the remainder of the world would have written off the browser as unusable. And even when the Working Group determined to alter the specification to match IE’s habits, Netscape would then have confronted precisely the identical drawback.
Thus DOCTYPE switching was created. The complete regime of “requirements mode” and “quirks mode” was born of this drawback. The options to different issues had been rolled into DOCTYPE switching, however the field mannequin triggered it. Give it some thought: as a result of two distributors did issues in a different way, browsers now have to take care of two totally different major rendering fashions and select which to make use of based mostly on an SGML declaration that claims nothing about rendering.
Moreover, the primary wave of CSS hacks had been devised to handle precisely the identical drawback. The basic instance of the style provides it away within the title: The Field Mannequin Hack. The truth is, the hack itself was based mostly on flaws in syntactical parsing of voice-family values, however no one ever known as it “the voice-family hack.”
The humorous half is that this wasn’t the one occasion the place a field mannequin inconsistency led to bother. Not lengthy after DOCTYPE switching saved CSS, the Explorer staff applied some options of CSS positioning. One of many properties they applied was clip. Having discovered their lesson with the field mannequin brouhaha, the engineers at Microsoft paid very shut consideration to the specification and did what it stated.
Shortly after they shipped it publicly, the CSS Working Group massively modified the best way clip labored. The syntax appeared precisely the identical, however yielded very totally different outcomes.
As soon as extra, the specification clashed with the habits of a publicly out there browser (or, should you choose, vice versa). The eventual decision was to revert to the sooner habits and drop the brand new habits solely. That renders clip successfully ineffective on any factor with unpredictable peak and width—which is to say, any normal-flow, non-replaced factor comparable to a div or a paragraph. Though different options had been proposed, they by no means got here to move, and clip withered away.
Think about a distinct consequence#section3
Suppose that as an alternative of implementing clip, the IE staff had applied -ms-clip. In that case, a habits change in a later specification wouldn’t have been so tough to beat. As a result of a vendor prefix marks a property as “in progress,” it’s a lot simpler for a vendor to return and alter it. Thus the IE staff may have modified the best way -ms-clip labored of their subsequent launch, explaining to builders that they had been updating their experimental implementation to match modifications to the specification.
Even when they’d determined that that was unattainable to do, the harm of the “dangerous” implementation would have been quarantined within the prefixed model of the property. Different distributors may have applied the brand new model of clip (utilizing their very own prefixes), unaffected by what the IE staff had achieved. A single vendor couldn’t pin the specification and different distributors in place by their actions.
That is the promise that prefixes present: A strategy to mark properties as “in progress,” and so not essentially assured to all the time act the identical in future releases; an out for distributors who must make these modifications; and a protection in opposition to dangerous or untimely implementations that occur to ship first. They add sorely wanted flexibility to the development of CSS.
After all, we may simply say: “When a browser is flawed in accordance with the specification, then they’ve to alter even when it breaks the structure of internet sites.” With prefixes, that’s quite a bit simpler to perform, because of the warning that prefixes embody. With out prefixes, it’s very tough and even unattainable. Microsoft by no means did change the best way it dealt with width and peak in legacy pages—as an alternative, it used DOCTYPE switching to behave in a different way on new (theoretically extra “requirements compliant”) pages. It was a helpful and needed trick, however that form of trick solely works as soon as.
Lest you assume that each one this silliness is an artifact of historical past, listed here are two circumstances of inconsistency taking place proper now:
-
Mozilla and WebKit browsers render
box-shadowblurring very in a different way, and neither absolutely conforms to the specification. As I write this paragraph, a prolonged and heated debate is raging on the www-style mailing listing. No less than one, and presumably each, implementations should change the best way they deal with shadow blurring to attain interoperability. The identical holds true for any Microsoft or Opera implementations. -
Mozilla and WebKit browsers each assist gradients, however they use radically totally different syntaxes to attain the identical fundamental end result. Now think about a world the place the distributors had applied gradients with out the prefixes. You’d have three decisions:
- Decide which browser will get a gradient and which one doesn’t.
- Use CSS hacks or browser sniffing to serve up totally different types to totally different browsers.
- Stroll away from utilizing gradients solely.
And there are three decisions right here solely as a result of the gradients use wildly totally different worth syntaxes, thus opening the door to choice primary. In a case the place two implementations use the identical worth syntax however have very totally different results—as was true with
clip—then there are actually solely the final two choices: hack and sniff to ship completely totally different types, or simply stroll away.
We’ve seen this film performed out many occasions over the historical past of CSS. There’s no purpose to need to see it once more. It was dangerous sufficient the primary dozen occasions.
However are prefixes actually any higher? In any case, it’s been stated that vendor prefixes are the brand new CSS hacks. As Aaron Gustafson identified in a latest article, this:
-moz-border-radius: 10px 5px;
-webkit-border-top-left-radius: 10px;
-webkit-border-top-right-radius: 5px;
-webkit-border-bottom-right-radius: 10px;
-webkit-border-bottom-left-radius: 5px;
border-radius: 10px 5px;
…is paying homage to this:
padding: 10px;
width: 200px;
width: 180px;
peak: 200px;
peak: 180px;
When it comes to repetition and annoyance, sure, the 2 are very a lot alike. However they’re essentially totally different on this approach: Prefixes give us management of our hacking future. Previously, we needed to invent a bunch of parser exploits simply to get inconsistent implementations to behave the identical as soon as we discovered they had been inconsistent. It was an entirely reactive strategy. Prefixes are a proactive strategy.
Moreover, prefixes are a short lived hack. As time goes on and implementations turn out to be constant, browsers will drop the prefixes. From then on, authors will be capable of write one line for border-radius as an alternative of six-plus strains of CSS. With out them, we’re simply ready for the subsequent botched implementation that forces us to assist it by way of hacks for years upon years.
That’s why making a unified prefix, comparable to -beta- or -w3c-, is at the very least half a step backwards. It might protect distributors’ means to mark properties as “in progress” and make modifications as wanted. Sadly, it could utterly rob authors of the power to excise, and even feed a distinct worth to, one specific browser if it has a botched implementation. From an creator’s perspective, a unified prefix isn’t any higher than a world with out prefixes.
I typically really feel the identical approach about pre-processor strategies to deal with prefixes, whether or not on the server aspect (utilizing instruments like Much less) or shopper aspect (any variety of JS frameworks). When utilizing these instruments, it’s potential to only write border-radius declarations and have the device develop that into the requisite listing of prefixed declarations. On the one hand, they’re a really helpful strategy to cut back typing and maintain the authoring neat and clear. On the opposite, they’re similar to a unified-prefixed or unprefixed world: one dangerous browser implementation away from breaking pages.
The benefit is that if one thing goes haywire, any creator can return, disable the pre-processor, and write out the prefixes by hand. Alternatively, the pre-processor will be up to date to deal with the issue. Both approach it’s a bit of extra cognitive overhead for the creator, however not an excessive amount of.
The draw back is extra philosophical, however it’s no much less essential for that: By hiding the prefixed properties behind a processor, authors might overlook that what they’re utilizing is experimental and topic to alter. Cognitively, they might begin to deal with what they’re utilizing as settled and secure when it might be nothing of the type.
Make prefixes actually matter#section6
I consider so firmly that vendor prefixes are a very good factor that I’m ready to take the subsequent logical step: Vendor prefixes must be made extra central to the requirements course of. They need to be required of newly applied properties and must be the mechanism by which interoperability is said.
Right here’s what I imply: Suppose somebody invents a brand new property known as text-curl. Instantly, three distributors implement it. Every of them must be required so as to add a vendor prefix to their implementation. Thus, we’d see issues like this:
h1 {
-webkit-text-curl: minor;
-moz-text-curl: minor;
-o-text-curl: minor;
text-curl: minor;
}
Over time, the distributors refine their implementations in response to bug studies and clarifications by the Working Group. Finally, the Working Group decides that two of the three are absolutely interoperable. These implementations then get to assist the naked text-curl. The third doesn’t.
At that time, authors would possibly determine to simplify their types like so:
h1 {
-webkit-text-curl: minor;
text-curl: minor;
}
As a substitute of hacks proliferating over time, they’re peeling away. Finally, we’ll solely want a single text-curl line.
So what occurs when a brand new implementation debuts? It makes use of the prefix in its first launch, regardless of what number of interoperable implementations exist already. Which may imply that we’d have to return and alter the CSS to say:
h1 {
-ms-text-curl: minor;
text-curl: minor;
}
Then, as quickly because the Working Group deems the implementation of -ms-text-curl interoperable, the prefix will be dropped within the subsequent launch of IE. At that time the CSS will be lowered to a single, unprefixed line. Once more, the variety of hacks dwindles over time.
After all, every of these distributors will proceed to assist the prefixed properties, so even when we don’t prune the prefixed strains, every supporting browser will acknowledge the unprefixed property and use it (because it comes after the prefixed declaration). For any browser that implements a prefixed model that doesn’t handle to get to an unprefixed state, its personal prefixed property will nonetheless work. Even when the CSS is rarely touched once more, it’ll proceed to operate.
Having stated that, return for a second to the time when the Working Group stated that two implementations had been interoperable and will thus drop the prefixes. That serves two functions. First, as I stated earlier than, it marks a property as having sufficient interoperability to permit progress within the requirements course of.
However the different factor it does—and that is arguably extra essential—is pressure the distributors and the Working Group to work collectively to plan the exams needed to find out interoperability. These exams can then information those that observe, serving to them to attain interoperable standing a lot quicker. They may actually ship the prefixed implementation in a single public beta and drop the prefix within the subsequent.
This reverses the best way issues are achieved now. Because it stands, the method is ready up in order that when any CSS module reaches the Candidate Suggestion stage, distributors can drop the prefixes from properties in that module. However that simply opens us as much as the opportunity of one other botched implementation and a way forward for hacks to work across the error.
As proposed right here, a module could be permitted to succeed in Candidate Suggestion as soon as all of its properties had at the very least two unprefixed implementations within the wild. Any implementations that got here after would begin prefixed and drop the prefix as soon as they’d confirmed, within the wild, that their prefixed implementation matched the present unprefixed implementations. As a substitute of being a minor gamble, unprefixed properties would come as near a assure as something we’ve seen so far.
If the historical past of net requirements has proven us something, it’s that hacks shall be needed. By front-loading the hacks utilizing vendor prefixes and enshrining them within the requirements course of, we are able to really repair a few of the potential issues with the method and presumably speed up CSS improvement.
So the subsequent time you end up grumbling about declaring the identical factor 4 occasions, as soon as for every browser, keep in mind that the ache is momentary. It’s a bit of like a vaccine—the shot hurts now, true, however it’s actually not that dangerous compared to the illness it prevents. And on this case, you’re being vaccinated in opposition to a nasty case of multi-year parser hacking and browser sniffing. We suffered by way of that lengthy plague as soon as already. Prefixes will, if used correctly, keep at bay one other outbreak for a very long time to come back.
