[OpenJDK 2D-Dev] [PATCH] Make automatic font substitution on macOS work for surrogate pairs

[Phil Race]

I have submitted https://bugs.openjdk.java.net/browse/JDK-8169202

Can you restart this thread with the proper format for a review request
as the subject

"RFR: 8169202: macos] Font substitution does not work for supplementary 
characters"

-phil.

On 11/03/2016 07:23 AM, Dmitry Batrak wrote:
> Added an automated version of the test to the webrev - 
> http://cr.openjdk.java.net/~avu/rfe_surrogates/webrev.01/ 
> <http://cr.openjdk.java.net/%7Eavu/rfe_surrogates/webrev.01/>
>
> Best regards,
> Dmitry Batrak
>
> On Tue, Nov 1, 2016 at 5:40 PM, Sergey Bylokhov 
> <Sergey.Bylokhov at oracle.com <mailto:Sergey.Bylokhov at oracle.com>> wrote:
>
>     Looks fine to me, but the jtreg test will be helpful.
>
>     On 27.10.16 11:56, Dmitry Batrak wrote:
>
>         Sure, here's the simplest test, that can be used for visual
>         inspection:
>
>         import javax.swing.*;
>         import java.awt.*;
>
>         public class SurrogatesFallbackTest {
>             public static void main(String[] args) {
>                 SwingUtilities.invokeLater(() -> {
>                     JFrame frame = new JFrame();
>                     JLabel label = new JLabel(new
>         String(Character.toChars(0x1d400))); // MATHEMATICAL BOLD
>         CAPITAL A
>                     label.setFont(new Font("Menlo", Font.PLAIN, 36)); //
>         expected to fallback to STIXGeneral
>                     frame.add(label);
>                     frame.pack();
>                    
>         frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
>                     frame.setLocationRelativeTo(null);
>                     frame.setVisible(true);
>                 });
>             }
>         }
>
>         I can convert it to an automatic test (rendering to a bitmap and
>         comparing the result to rendering of 'missing' glyph), and add
>         it to the
>         webrev, if that makes sense.
>
>         Best regards,
>         Dmitry Batrak
>
>         On Thu, Oct 27, 2016 at 2:17 AM, Philip Race
>         <philip.race at oracle.com <mailto:philip.race at oracle.com>
>         <mailto:philip.race at oracle.com
>         <mailto:philip.race at oracle.com>>> wrote:
>
>             Hi,
>
>             I can file a bug on this if I can't find one.
>             If you can email me the test it will help even if it is
>         not checked in.
>
>             -phil.
>
>             On 10/26/16, 6:28 AM, Dmitry Batrak wrote:
>
>                 Hello,
>
>                 I'd like to propose a patch to make automatic font
>             substitution on
>                 macOS work for surrogate pairs.
>                 I have a Contributor status via agreement signed by
>             JetBrains,
>                 hope someone can sponsor the patch.
>
>                 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.
>
>                 I didn't include a test for this change, as it would
>             depend on
>                 OS-specific font fallback mechanism
>                 and fonts installed, but I can create one that will
>             work on a
>                 latest version of macOS with default
>                 fonts, if needed.
>
>                 Webrev for the fix is available at
>             http://cr.openjdk.java.net/~avu/rfe_surrogates/webrev.00/
>             <http://cr.openjdk.java.net/%7Eavu/rfe_surrogates/webrev.00/>
>                
>             <http://cr.openjdk.java.net/%7Eavu/rfe_surrogates/webrev.00/
>             <http://cr.openjdk.java.net/%7Eavu/rfe_surrogates/webrev.00/>>
>                 (kindly posted by my colleague, having access to
>             cr.openjdk.java.net <http://cr.openjdk.java.net>
>             <http://cr.openjdk.java.net>).
>
>                 To my knowledge, there's no ticket in OpenJDK issue
>             tracker for
>                 the proposed enhancement.
>                 I can submit it via http://bugs.java.com/, if that's
>             an obstacle.
>
>                 Best regards,
>                 Dmitry Batrak
>
>
>
>
>
>         --
>         Dmitry Batrak
>         Senior Software Developer
>         JetBrains
>         http://www.jetbrains.com
>         The Drive to Develop
>
>
>
>     -- 
>     Best regards, Sergey.
>
>
>
>
> -- 
> Dmitry Batrak
> Senior Software Developer
> JetBrains
> http://www.jetbrains.com
> The Drive to Develop

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