Re: Intent to unprefix: ::-moz-selection.

[Emilio Cobos Álvarez]

In the CSSWG April F2F in Berlin this was extensively discussed and the 
CSSWG allowed / recommended us to unprefix this despite changing the spec.


Just landed the change unprefixing this on inbound, let me know if you 
see something broken because of it.


Thanks!

 -- Emilio

On 3/26/18 9:16 AM, Emilio Cobos Álvarez wrote:

Hi,

In bug 509958 I intend to unprefix the ::-moz-selection pseudo-element.

The situation here is not great wrt the spec saying what we do, or what
other implementations do for that matter, see [1].

However other engines have shipped this unprefixed for a long time with
the same semantics that we implement, and we're seeing webcompat
problems due to people forgetting to include ::-moz-selection in their
style sheets, see bug 1427680 or bug 1448670 for some examples.

Given I don't think other engines have any incentive to implement what
the spec says (given it's slower, and has the chance of giving them
webcompat headache), and that we're compatible with them, I proposed to
adapt the spec to reality in that spec issue, and unprefix our
pseudo-element.

Let me know if there's any concerns with this plan. Thanks!

  -- Emilio

[1]: https://github.com/w3c/csswg-drafts/issues/2474
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Re: Intent to unprefix: ::-moz-selection.

[Emilio Cobos Álvarez]

Sorry for not following up on this earlier, Ehsan, somehow this slipped 
through my inbox.


On 4/6/18 1:26 AM, Ehsan Akhgari wrote:

::-moz-selection seems like a fairly popular feature.  PublicWWW claims
it's seen on a million sites:
https://publicwww.com/websites/%22%3A%3A-moz-selection%22/

After this change, is it feasible to detect the usage of the prefixed
pseudo-element so that existing code that uses ::-moz-selection would emit
a helpful console warning?  It would be nice to have a way to communicate
to web developers that they can now remove the Gecko specific rules.


It is feasible, but it's not clear to me how worth it is to land this 
now. In particular, we're going to keep parsing ::-moz-selection for now 
as an alias, since as you mentioned it's a fairly popular feature, and 
people won't be able to remove it for a while if they want to support 
ESR and similar.


If we decide to remove the prefixed version, developers would get a in 
the console automatically if they have the CSS error filter enabled that 
would look like:


  Unknown pseudo-class or pseudo-element ‘-moz-selection’.  Ruleset 
ignored due to bad selector.


Which should be enough to hint them that they can remove it.

 -- Emilio


On Mon, Mar 26, 2018 at 9:21 AM Emilio Cobos Álvarez 
wrote:


Hi,

In bug 509958 I intend to unprefix the ::-moz-selection pseudo-element.

The situation here is not great wrt the spec saying what we do, or what
other implementations do for that matter, see [1].

However other engines have shipped this unprefixed for a long time with
the same semantics that we implement, and we're seeing webcompat
problems due to people forgetting to include ::-moz-selection in their
style sheets, see bug 1427680 or bug 1448670 for some examples.

Given I don't think other engines have any incentive to implement what
the spec says (given it's slower, and has the chance of giving them
webcompat headache), and that we're compatible with them, I proposed to
adapt the spec to reality in that spec issue, and unprefix our
pseudo-element.

Let me know if there's any concerns with this plan. Thanks!

  -- Emilio

[1]: https://github.com/w3c/csswg-drafts/issues/2474
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Re: Intent to unprefix: ::-moz-selection.

[Emilio Cobos Álvarez]

On 03/28/2018 12:09 AM, twisniew...@mozilla.com wrote:
> On Tuesday, March 27, 2018 at 4:38:56 PM UTC-4, Emilio Cobos Álvarez wrote:
>> That looks like an easy fix though, I'll ensure it gets fixed before 
>> landing. Filed bug 1449010.
>  
> If it helps, I had a patchset for this in bug 292563, but ran into an odd 
> reftest failure that I never had time to figure out.

Ah, I see, interesting!

I used negative reftests (!=) to test this, instead of just trying to
overlay the image, which looks a little bit more fragile.

Given my patch just landed, I'll dupe that bug. Thanks!

 -- Emilio

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Re: Intent to unprefix: ::-moz-selection.

[twisniewski]

On Tuesday, March 27, 2018 at 4:38:56 PM UTC-4, Emilio Cobos Álvarez wrote:
> That looks like an easy fix though, I'll ensure it gets fixed before 
> landing. Filed bug 1449010.
 
If it helps, I had a patchset for this in bug 292563, but ran into an odd 
reftest failure that I never had time to figure out.
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Re: Intent to unprefix: ::-moz-selection.

[Emilio Cobos Álvarez]

On 3/26/18 4:13 PM, Boris Zbarsky wrote:

On 3/26/18 3:16 AM, Emilio Cobos Álvarez wrote:

However other engines have shipped this unprefixed for a long time with
the same semantics that we implement


https://bugzilla.mozilla.org/show_bug.cgi?id=509958#c14 claims the 
semantics are not actually quite the same.  Have we done some testing 
here?  Including on Edge?


So, when I went through the bug I didn't know at all what that comment 
was about (and the account that posted it was gone so couldn't ask), but 
it seems we don't respect the ::selection background when selecting images.


That looks like an easy fix though, I'll ensure it gets fixed before 
landing. Filed bug 1449010.


It would be best to just have matching 
semantics, instead of unprefixing with slightly different behavior.


Haven't tested Edge (because I don't have it locally), but will make 
sure that gets done before landing that patch.


 -- Emilio


-Boris
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Re: Intent to unprefix: ::-moz-selection.

[Boris Zbarsky]

On 3/26/18 3:16 AM, Emilio Cobos Álvarez wrote:

However other engines have shipped this unprefixed for a long time with
the same semantics that we implement


https://bugzilla.mozilla.org/show_bug.cgi?id=509958#c14 claims the 
semantics are not actually quite the same.  Have we done some testing 
here?  Including on Edge?  It would be best to just have matching 
semantics, instead of unprefixing with slightly different behavior.


-Boris
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