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Re: [css4-ui] ::tooltip

From: Brad Kemper <brad.kemper@gmail.com>
Date: Fri, 13 Apr 2012 10:18:34 -0700
Message-Id: <F3319912-C24E-40C1-9472-2EEF50DAFE7C@gmail.com>
Cc: Divya Manian <manian@adobe.com>, Andrew Fedoniouk <news@terrainformatica.com>, Lea Verou <leaverou@gmail.com>, "www-style@w3.org" <www-style@w3.org>
To: "Tab Atkins Jr." <jackalmage@gmail.com>
On Apr 13, 2012, at 9:18 AM, "Tab Atkins Jr." <jackalmage@gmail.com> wrote:

> On Fri, Apr 13, 2012 at 8:28 AM, Brad Kemper <brad.kemper@gmail.com> wrote:
>> On Apr 13, 2012, at 8:14 AM, "Tab Atkins Jr." <jackalmage@gmail.com> wrote:
>>> On Fri, Apr 13, 2012 at 6:32 AM, Brad Kemper <brad.kemper@gmail.com> wrote:
>>>> For some pseudo-elements, you can grab content from elsewhere. We have 'content' and 'flow-from' (regions) that could provide that content for '::tooltip'. 'Content' could grab it from the 'title' attribute, like this:
>>>> 
>>>> div::tooltip { content: attr(title); background: gold; font-size: x-large;  }
>>>> 
>>>> In this case, if no title attribute exists, then there is no content. If there is no content, then the pseudo-element does not appear (just as with '::before' and '::after'). So we don't actually need '[title]' in the selector.
>>> 
>>> Actually, you do, as attr() will return the empty string in that case,
>>> and the empty string is a valid value for 'content' that should cause
>>> it to be generated.
>> 
>> Is that considered useful? Why not null if the attribute doesn't exist, and empty string it exists with no value or empty value?
> 
> Because attr() needs to have a specific type, and in that expression
> the type is "string".  If attr() could return multiple types we can't
> detect syntax errors with it.
> 
> Also, null isn't a CSS value. ^_^

OK, but it could just make it invalid if the attribute didn't exist, couldn't it?

> (You could, of course, instead do "content: attr(title, none);".  The
> default value doesn't need to be of the declared type.)

And that is useful?
Received on Friday, 13 April 2012 17:19:11 GMT

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