[OpenJDK 2D-Dev] RFR: 8169202: [macos] Font substitution does not work for supplementary characters

[Phil Race]

   29 import java.awt.*;

We avoid wild card imports - even in tests.

Can you provide a pointer to any Apple docs on UnicodeScalarValue.
I can't find it .. I presume its a typedef of int so it can hold a composed
unicode code point outside the BMP ..

By already existing support I guess you refer to this :-

  592 CGGI_CreateImageForUnicode
  593     (CGGI_GlyphCanvas *canvas, const AWTStrike *strike,
  594      const CGGI_RenderingMode *mode, const UnicodeScalarValue uniChar)
...
  602     if (uniChar > 0xFFFF) {
  603         UTF16Char charRef[2];
  604         CTS_BreakupUnicodeIntoSurrogatePairs(uniChar, charRef);
...


This code was a bit more work to review than I was expecting because
of having to follow things around to see if numGlyphs != num16bitChars
was a problem or if the "non-negative" cases where we already have
a glyph were handled properly. And I'm still not entirely sure.
What reg. tests and other general testing has been done with this fix ?

-phil.


On 11/07/2016 06:52 AM, Dmitry Batrak wrote:
> Hello,
>
> I'd like to propose a patch for 
> https://bugs.openjdk.java.net/browse/JDK-8169202.
> I have a Contributor status via agreement signed by JetBrains, hope 
> someone can sponsor the patch.
> This repeats the proposal I've sent earlier to this mailing list,
> adding now a reference to the created OpenJDK issue.
>
> Currently, if requested font cannot render a Unicode character 
> represented by a surrogate pair,
> no substitution is performed - Font.canDisplay will return false, and 
> the character will be
> rendered as a 'missing' glyph. This behaviour doesn't violate any 
> specification, but it looks like
> it can be easily improved, as underlying OS framework used under the 
> hood does support surrogate pairs.
>
> The proposed change consists of two parts. First part is adjusting the 
> code in CoreTextSupport.m
> to handle surrogate pairs while performing char-to-glyph mapping, by 
> encoding non-displayable
> surrogate pairs using negative values of the codepoint, similar to how 
> non-displayable BMP characters
> are encoded. Second part is fixing the rendering code (in 
> CGGlyphImages.m), where wrong type was used
> to pass character values around, so that code for surrogate pairs 
> handling, already present there,
> could work.
>
> Webrev for the fix is available at
> http://cr.openjdk.java.net/~avu/JDK-8169202/webrev.02/ 
> <http://cr.openjdk.java.net/%7Eavu/JDK-8169202/webrev.02/>
> (kindly posted by my colleague, having access to cr.openjdk.java.net 
> <http://cr.openjdk.java.net>).
>
> Best regards,
> Dmitry Batrak

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