[OpenJDK 2D-Dev] <AWT Dev> [10] Review Request: 8182410, 8183508, 8181289

Jonathan Gibbons jonathan.gibbons at oracle.com
Wed Nov 22 22:53:44 UTC 2017


I have reconstructed a very simple, very artificial example to demo the 
bug.   This example uses lots of filler text, but while that is 
artificial, for sake of recreating a demo,  note that the problem first 
appeared, for real, in real JDK 9 API documentation with extended doc 
comments, and that as a result, we followed the advice I have been 
trying to give you.

See the toy API bundle here:

There are two modules, modA and modB.  Both have huge long doc comments, 
with a heading at the top and a link at the bottom.

In modA, the anchor is of the form <h1 id="head">.  In modB, the anchor 
is of the form <a id="head">.

In each of these files, scroll to the end of the comment, and look for a 
link, called "link", at the bottom of the page.  In both cases, the page 
scrolls so that the heading is near the top of the browser window, but 
in one case it is hidden under the javadoc navbar, and in the other 
case, it is clearly visible, below the javadoc navbar.

This is the difference in behavior that I can been trying to describe to 
you. I'm using Ubuntu 14.04 with Firefox 38, but I'm not the only one to 
have seen this effect.  I don't know whether you will get the same 
effect in your browser, but the fact that there is a reasonable 
OS/browser combo that demonstrates the problem is enough of a reason to 
avoid provoking the problem unnecessarily. If you don't see the problem 
on your browser, but want to see it in mine, I see you are in SCA22, so 
drop by my office for a demo.

I'll leave it to the AWT team to decide what to do about this 
bug/review. I still recommend updating what is necessary to fix issues, 
and not otherwise changing the doc comments unnecessarily, and not 
changing them in a way to provoke this bad behavior.

-- Jon

On 11/22/2017 12:10 PM, Semyon Sadetsky wrote:
> Hi Jon,
> This is not only about HTML5 spec, I also hardly can find resources 
> that follow your "<a id=" rule. And I doubt that cross-browser 
> compatibility is important for Javadoc only and others do not care 
> about their readers. So, I asked you for an examples of such 
> workaround or a reference to a bug filed against any browser. Fragment 
> identifiers is too important functionality to let this issue be 
> unnoticeable.
> You are correct that there is no bug here. But a bug was absent  
> before this fix as well. This bug is about following to the HTML5 
> standards, so let's follow them in full and not to return to this once 
> again. We have a good chance to provide documentation in clean HTML5 
> after the fix without any workarounds.
> --Semyon
> On 11/14/2017 09:16 AM, Jonathan Gibbons wrote:
>> Semyon,
>> I read the HTML 5 spec the same as you, and we (on the Javadoc team) 
>> started using id on other elements, as well as <a> to provide a 
>> target that could be linked to.
>> However, the pragmatic experience was that the scrolling in some 
>> browsers did not completely reveal the element when there was a 
>> layered z component involved: the target element sometimes ended up 
>> under that layered component. Our experience was that the behavior 
>> was fixed when the target identifier was in an <a> element.
>> So, yes, you can follow the rules, and suggest that it is OK to put 
>> id on any element, and use it as a fragment identifier in a link, as 
>> given in the spec. Or you can be nice to your readers, and workaround 
>> what is probably a display bug in some browsers.
>> In the case of this review, you were suggesting additional "cleanup" 
>> on code that worked. Since there was no bug involved, and thus no 
>> inherent need to fix the code, my review feedback is to leave the 
>> code alone.  You may choose to insist differently, and I cannot say 
>> that what you are suggesting is against the spec; I can just say that 
>> we can seen cases where such changes leads to bad visual effects.
>> -- Jon
>> On 10/25/17 6:31 PM, Semyon Sadetsky wrote:
>>> Hi Jonathan,
>>> On 10/24/2017 03:20 PM, Jonathan Gibbons wrote:
>>>> Semyon,
>>>> Although id is a global attribute and can be used to identify any 
>>>> node, some browsers do better navigation/scrolling when the id is 
>>>> in an <a> tag.  We have seen poor autoscrolling behavior when the 
>>>> id is an a header tag, such that the header ends up obscured under 
>>>> the navigation bar at the top of the page.
>>> You probably meant heading elements, because "header tag" is 
>>> something different. Do you have any references those issues 
>>> reports? Because in html5 the fragment identifiers are the only 
>>> correct way to have internal document bookmarks [1] [2]. If some 
>>> browsers do not navigate to fragment identifiers except for <a> 
>>> element there must be bugs reported that  which will be fixed soon.
>>> The html5 specification is very specific about navigating to the 
>>> fragment identifier [3]. So, there should no be difference between 
>>> navigating to "<a id=" or to any other element having id attribute. 
>>> If you just need an extra vertical space above header you could use 
>>> css style or <p>, but usage of <a> as an upper margin seems odd 
>>> since it is a special tag.
>>> --Semyon
>>> [1] https://www.w3schools.com/html/html_links.asp
>>> [2] http://www.html5-tutorials.org/html-basics/links/
>>> [3] https://www.w3.org/TR/html5/browsers.html#scroll-to-fragid
>>>> -- Jon
>>>> On 10/23/2017 10:08 PM, Semyon Sadetsky wrote:
>>>>> Hi Sergey,
>>>>> I see no reason to have an extra empty anchor tag to set a 
>>>>> bookmark. The id attribute works with any element.
>>>>> For example:
>>>>>     <a id="Definitions"></a>
>>>>>     <h3>Definitions</h3>
>>>>> should be
>>>>>     <h3 id="Definitions">Definitions</h3>
>>>>> --Semyon
>>>>> On 10/23/2017 02:42 PM, Sergey Bylokhov wrote:
>>>>>> Hello,
>>>>>> Please review the fix for.
>>>>>> 8182410: missing 'title' in 
>>>>>> api/javax/swing/plaf/synth/doc-files/componentProperties.html
>>>>>> 8183508: multi_tsc.html should be updated
>>>>>> 8181289: Invalid HTML 5 in AWT/Swing docs
>>>>>> Description:
>>>>>>  - Illegal characters were removed.
>>>>>>  - Unsupported tags/properties were removed -like <tt>, <center>, 
>>>>>> font, etc.(except the tags related to tables which I'll fix later).
>>>>>>  - HTML5 doctype is set for all files.
>>>>>>  - The <title> is set for all files.
>>>>>>  - <a name="" is replaced by <a id=""
>>>>> Why you replace
>>>>>>  - Copyrights were added to some files.
>>>>>> Note that I placed a <head> tag before copyright to solve errors 
>>>>>> like:
>>>>>> "A charset attribute on a meta element found after the first 1024 
>>>>>> bytes. Fatal Error: Changing encoding at this point would need 
>>>>>> non-streamable behavior"
>>>>>> specdiff: 
>>>>>> http://cr.openjdk.java.net/~serb/8181289/specdiff/overview-summary.html 
>>>>>> Bugs:
>>>>>> https://bugs.openjdk.java.net/browse/JDK-8182410
>>>>>> https://bugs.openjdk.java.net/browse/JDK-8183508
>>>>>> https://bugs.openjdk.java.net/browse/JDK-8181289
>>>>>> Webrev can be found at: 
>>>>>> http://cr.openjdk.java.net/~serb/8181289/webrev.00

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