[OpenJDK 2D-Dev] freetypescaler fix for fonts that start with a control point

Phil Race philip.race at oracle.com
Tue Sep 9 21:47:45 UTC 2014


Although I have yet to test it, the fix looks reasonable to me.
Probably this decompose outline function supporting
the callbacks was overlooked when this code was written.
A jtreg test is tricky as you need to have font data available that 
the buggy case and then use the resulting Path2D. But there is no way
to rely on a particular font with a known property being available
without creating one and checking it in .. that might be overkill.

Plus how do you test this in an automated way ?
You can't compare the freetype glyph rasterisation with the pisces 
rasterisation (that done using fill(..))
as they are highly likely to differ in some tiny ways and knowing how 
much difference to
allow is fraught too, leading to a fragile test.

So noreg-hard and some alternative testing which likely involves a manual
run through Font2DTest to make sure everything seems good.
I think SQE have some image comparison testing but even if they cover much
outline font rendering which I doubt, I don't think they run it on the 
open builds very often

FWIW the test code could have been simpler as in :-

    public static void writeImage(File fontFile, File outputFile, String 
value) throws Exception {
         BufferedImage image = new BufferedImage(200, 200, 
         Graphics2D g = image.createGraphics();
         g.fillRect(0, 0, image.getWidth(), image.getHeight());

         Font font = Font.createFont(Font.TRUETYPE_FONT, fontFile);
         font = font.deriveFont(Font.PLAIN, 72f);
         FontRenderContext frc = new FontRenderContext(null, false, false);
         GlyphVector gv = font.createGlyphVector(frc, value);
         g.drawGlyphVector(gv, 10, 80);
         g.fill(gv.getOutline(10, 180));
         ImageIO.write(image, "png", outputFile);

and then you don't need that G2D subclass.

There should of course be a client-libs/2d bug on this.
I submitted https://bugs.openjdk.java.net/browse/JDK-8057986

Next thing to do is test the fix on an openjdk build using Font2DTest.


On 9/5/2014 6:57 PM, Martin Buchholz wrote:
> Hi font friends!
> I'm trying to share a font rendering bug fix contributed by my 
> colleagues Behdad and Igor.
> http://cr.openjdk.java.net/~martin/webrevs/openjdk9/freetypeScaler-outline/ 
> <http://cr.openjdk.java.net/%7Emartin/webrevs/openjdk9/freetypeScaler-outline/>
> Repro recipe:
> (cd test/java/awt/font/GlyphVector/ && javac GlyphVectorOutline.java 
> && wget -q -O/tmp/msgothic.ttc 
> https://browserlinux-jp.googlecode.com/files/msgothic.ttc && java 
> GlyphVectorOutline /tmp/msgothic.ttc /tmp/katakana.png)
> After successfully running that, examine the two rendered Japanese 
> characters.
> Without our fix, the lower one is misrendered.
> I don't know how the fix works, and whether/how the manual test case 
> can be turned into a real jtreg test.

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