[OpenJDK 2D-Dev] [8u] RFR 8201801: RTL language (Hebrew) is presented from left to right

[Dmitry Markov]

Hi Phil,

Thank you for the comments. You are right the invocation of isAAT() method might be too expensive especially on OSX. I have changed the if-statement as you suggested. Please find the new webrev here: http://cr.openjdk.java.net/~dmarkov/8201801/jdk8u/webrev.02/

Also I will be happy to port the fix for JDK-8210384 to 8u once it is ready.

Thanks,
Dmitry

> On 4 Sep 2018, at 20:34, Phil Race <philip.race at oracle.com> wrote:
> 
> I see you noticed the problem with it not necessarily being an AAT font.
> It seems this method is a copy/paste of the method added in JDK 9.
> So this will work but looking at it, I think in JDK 9 I should have made this more efficient.
> Probably it was a detail in the larger work, that I never came back to.
> On MacOS where it calls through the PhysicalFont interface, since CFont is not a TrueTypeFont,
> it will be retrieving all the data in the table from native to Java on every call to layout. That will be expensive.
> 
> You can mitigate this in your case by reversing the order here 
> +        if (isAAT(font) && (typo_flags & 0x80000000) != 0) {
> 
> to
> +        if (((typo_flags & 0x80000000) != 0) && isAAT(font)) {
> 
> So it will only take the hit for RTL text which will save a lot of cases  ...
> I have filed https://bugs.openjdk.java.net/browse/JDK-8210384 <https://bugs.openjdk.java.net/browse/JDK-8210384> which I will fix for 12.
> 
> Up to you whether you also want to wait for that fix, or just update as I have suggested
> and maybe take a follow-on fix later.
> 
> Note that whilst your fix will at least make sure text reads in the correct direction, it
> means it will be using default built-in shaping rules of ICU and so may miss at least
> some features provided by the font.
> 
> -phil.
> 
> On 09/03/2018 05:54 AM, Dmitry Markov wrote:
>> Hi Prasanta,
>> 
>> Thank you for the feedback. I missed the usage of OSX specific class in shared code for some reasons. Please find the updated webrev here: http://cr.openjdk.java.net/~dmarkov/8201801/jdk8u/webrev.01/ <http://cr.openjdk.java.net/%7Edmarkov/8201801/jdk8u/webrev.01/>
>> I replaced the usage of CFont with a new private method which tests either a font is AAT or not.
>> 
>> The issue is jdk8u (ICU) specific. It does not take place on jdk12 because starting from jdk9 we use Harfbuzz as default layout engine.
>> 
>> Thanks,
>> Dmitry 
>> 
>>> On 3 Sep 2018, at 11:33, Prasanta Sadhukhan <prasanta.sadhukhan at oracle.com <mailto:prasanta.sadhukhan at oracle.com>> wrote:
>>> 
>>> Hi Dmitry,
>>> Not going into technicalities of the fix, but it seems it will break non-macos build as you are checking for CFont in a shared class?
>>> Also, if it's the issue still exists, then why you are fixing only in 8u and not in jdk12?
>>> 
>>> Regards
>>> Prasanta
>>> On 9/3/2018 3:20 PM, Dmitry Markov wrote:
>>>> Hello,
>>>> 
>>>> Could you review a fix for jdk8u, please?
>>>> 
>>>> 	bug: https://bugs.openjdk.java.net/browse/JDK-8201801 <https://bugs.openjdk.java.net/browse/JDK-8201801>
>>>> 	webrev: http://cr.openjdk.java.net/~dmarkov/8201801/jdk8u/webrev.00/ <http://cr.openjdk.java.net/%7Edmarkov/8201801/jdk8u/webrev.00/>
>>>> 
>>>> Problem description:
>>>> The fix for 7162125 [1] enabled font tables processing on OSX. However there is a lack of support for RTL languages in ICU layout engine. Quote from ICU guide: “…The AAT processing in the LayoutEngine is relatively basic as it only applies the default features in left-to-right text. This processing has been tested for Devanagari text. Since AAT processing is not script-specific, it might not work for other scripts…”, more details at http://userguide.icu-project.org/layoutengine <http://userguide.icu-project.org/layoutengine>
>>>> As a result all RTL languages on OSX are incorrectly laid out, (i.e. the letters are reversely presented).
>>>> 
>>>> Fix:
>>>> Skip font tables for RTL languages on OSX platform.  
>>>> 
>>>> Thanks,
>>>> Dmitry
>>>> 
>>>> [1] - https://bugs.openjdk.java.net/browse/JDK-7162125 <https://bugs.openjdk.java.net/browse/JDK-7162125>
>> 
> 

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