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List:       openjdk-2d-dev
Subject:    Re: [OpenJDK 2D-Dev] RFR: 8203485: [freetype] text rotated on 180 degrees is too narrow
From:       Sergey Bylokhov <Sergey.Bylokhov () oracle ! com>
Date:       2018-05-24 19:25:51
Message-ID: 74b93017-5c6d-6b03-8ca1-166b9869a54e () oracle ! com
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looks fine.

On 22/05/2018 09:56, Philip Race wrote:
> +1 (approved) from me.
> 
> -phil.
> 
> On 5/22/18, 9:40 AM, Andrew Brygin wrote:
> > corrected:
> > 
> > 47     static final Font fnt = new Font(Font.SERIF, Font.PLAIN, 12);
> > 
> > Updated webrev: http://cr.openjdk.java.net/~bae/8203485/webrev.01/
> > 
> > Thanks,
> > Andrew
> > 
> > > On May 22, 2018, at 7:26 PM, Philip Race<philip.race@oracle.com>  wrote:
> > > 
> > > Fix sounds good.
> > > 
> > > The test has a bug
> > > 47     static final Font fnt = new Font("Time New Roamn", 
> > > Font.PLAIN, 1).deriveFont(12.0f);
> > > 
> > > "Roamn" should be "Roman”.
> > > 
> > > But since Linux is very unlikely to have that font, I think you 
> > > should use Font.SERIF instead.
> > > 
> > > Actually I am unclear why you need to use deriveFont and can't
> > > test this with the constructor taking int of 12.
> > > 
> > > -phil
> > > 
> > > On 5/22/18, 8:50 AM, Andrew Brygin wrote:
> > > > Webrev: http://cr.openjdk.java.net/~bae/8203485/webrev.00/
> > > > 
> > > > Bug:
> > > > https://bugs.openjdk.java.net/browse/JDK-8203485
> > > > 
> > > > 
> > > > With freetype, text rotated on 180 or 270 degrees is too narrow.
> > > > Attached test case and screenshots demonstrate the problem.
> > > > 
> > > > The problem is caused by the rounding applied to the cases of vertical
> > > > and horizontal text, see freetypeScaler.c, lines 768 and 773:
> > > > 
> > > > http://hg.openjdk.java.net/jdk/client/file/80a5ff734fcd/src/java.desktop/share/native/libfontmanager/freetypeScaler.c#l768 \
> > > >  
> > > > 
> > > > 
> > > > http://hg.openjdk.java.net/jdk/client/file/80a5ff734fcd/src/java.desktop/share/native/libfontmanager/freetypeScaler.c#l773 \
> > > >  
> > > > 
> > > > 
> > > > The rounding routine is defined as ROUND(x) ((int) (x+0.5)) (see 
> > > > line 48),
> > > > and it gives incorrect results for negative arguments.
> > > > 
> > > > For example, say glyph advance is 8, and we render it without rotation,
> > > > and with rotation on 180 degrees. In these cases, we get ROUND(8) = 8,
> > > > whereas for 180 degrees we get ROUND(-8) = -7. This rounding error
> > > > leads to decrease of the width of the rendered text.
> > > > 
> > > > For the case of integer metrics, we can expect that FT26.6 advances
> > > > produced by freetype are integer, i.e. fractional part (lower 6 bits)
> > > > is zero. So, we can convert them to glyph info values without floating
> > > > point division, just by using integer shift. In this case, there is no
> > > > need to round the floating point value to integer, and there is no need
> > > > to care about sign of the argument.
> > > > 
> > > > Thanks,
> > > > Andrew
> > > > 


-- 
Best regards, Sergey.


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