[OpenJDK 2D-Dev] RFR: 8203485: [freetype] text rotated on 180 degrees is too narrow

[Sergey Bylokhov]

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 at 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.