[OpenJDK 2D-Dev] [9] RFR JDK-8147002:[macosx] Arabic character cannot be rendered on MacOS X

[Phil Race]

I think that so long as we are using JRS* in some places and CoreText's 
cascading list
in others there is the likelihood of some inconsistency where JRS 
introduces some magic
that we don't know about

So canDisplay() needs to be fixed to be consistent and perhaps we also 
need to see
if we are always getting the glyphs from the same fonts for the cases 
where there
is no missing glyph.

I do agree that getting away from JRS* support is the way to go so we 
are in control.
However not at this time in JDK 9.

Yes "." fonts are not enumerated by OS X but if you can find them they work.
This is how the UI fonts are handled.

Yes, we are aware this fixed it only for Oracle JDK.
The bit I missed is that GeezaProInterface was then used on OpenJDK by JRS.
So we could add that as well.
If you have any other fonts you think should be added to the tail of 
that list we
can add them too.

-phil.

On 02/10/2017 07:59 AM, Dmitry Batrak wrote:
> Hi,
>
> I've tried to build OpenJDK from 'client' repository with the fix, and the
> issue is still reproducible for me. Are you fixing it only for Oracle JDK
> (including Lucida Sans Regular font), and not for OpenJDK? The problem 
> is not
> that some character cannot be rendered using a particular font, it's that
> rendering behaviour doesn't match what 'canDisplay' returns.
>
> If you're interested I can share the way we've fixed this issue in our
> OpenJDK-based runtime.
>
> As you've mentioned, the problem is that
> JRSFontCreateFallbackFontForCharacters returns fallback font, which is 
> not on
> the cascaded font list, and it can be absent even in the whole list of 
> fonts
> reported by the system. On my machine, with OpenJDK, it's 
> .GeezaProInterface
> (with name starting with dot). I guess such fonts are treated by macOS as
> 'hidden' (just like files with names starting with dots), still they 
> seem to be
> usable from application if requested by their name.
>
> As JRSFontCreateFallbackFontForCharacters is a 'black box', it's hard 
> to make
> sure cascade list we're building matches its internal logic, so we've 
> chosen to
> build the list dynamically based on the output of
> JRSFontCreateFallbackFontForCharacters itself. I can try to prepare
> corresponding webrev, if you think that can be useful.
>
> Alternative solution (and, probably, a better one strategically), 
> would be not
> using JRSFontCreateFallbackFontForCharacters at all. The cascade list, 
> that is
> built currently, can probably be used to perform font fallback in all 
> cases.
>
> Best regards,
> Dmitry Batrak
>
>
> > Hi All,
> >
> > Please review a fix for an issue which causes arabic character "alef" to
> > be not rendered in osx for menlo font in italic style.
> >
> > Bug: https://bugs.openjdk.java.net/browse/JDK-8147002
> >
> > The issue was actually a regression caused by the fix to JDK-7162125:
> > [macosx] A font has different behaviour for ligatures depending on its
> > creation mode
> > in which we have added cascaded font list to find the real fonts that
> > CFont uses, so that there is no need to use "negative" glyph code for
> > finding the fallback fonts
> > using the "subsititution"/"fallback" mechanism used by osx code.
> >
> > However, the above logic of using cascaded font list in CFont does not
> > take into account of using JRE provided fonts like all those Lucida* ttf
> > in jdk/lib/fonts/, so
> > when a glyph (in this intance, arabic 'alef' character) is intended to
> > be rendered in Menlo font in italic style, osx will not be able to find
> > the glyph in Menlo-Italic font
> > and neither in all the cascaded system fonts provided by CoreText, so it
> > results in empty box.
> >
> > Before 7162125 fix, the fallback code in
> > CoreTextSupport.m#CTS_CopyCTFallbackFontAndGlyphForJavaGlyphCode() uses
> > JRSFontCreateFallbackFontForCharacters()
> > was adding jre/lib/fonts to the fallback list which was causing the
> > glyph to be found in "LucidaBrightRegular.ttf" font and the glyph was
> > rendered.
> >
> > So, the proposed fix is to add jre provided font "Lucida Sans Regular"
> > to the cascaded list so that we get the "alef" glyph.
> > The reason for choosing "Lucida Sans Regular" over "Lucida Bright
> > Regular" is, because it is the largest font file in jre and has all the
> > glyph codepoints that no other font in the jre has,
> > so we will not lose out on any codepoints and will help us in not
> > getting missing glyph.
> >
> > webrev: http://cr.openjdk.java.net/~psadhukhan/8147002/webrev.00/ 
> <http://cr.openjdk.java.net/%7Epsadhukhan/8147002/webrev.00/>
> >
> > Regards
> > Prasanta
>