[OpenJDK 2D-Dev] Fonts rendering in openjdk

[Aekold Helbrass]

Phil, thanx for your replies. I'll start digging into freetype.

Uploaded screenshots to picasa if you're interested:
http://picasaweb.google.com/Helbrass/Screenshots?feat=directlink

On 5/17/10, Phil Race <philip.race at oracle.com> wrote:
> On 5/17/2010 5:44 AM, Aekold Helbrass wrote:
>> Hi again!
>>
>> Thanx for you fast and informative responses!
>>
>> But now I am a bit confused. Roman tells that Freetype does the
>> rendering, but there is significant difference between Qt apps and
>> Java apps. See screenthos in attachments.
>>
>
> I think you misinterpreted. He's means that freetype produces the glyph
> images.
> There's no attachment. I think these mailing lists disallow them.
> freetype has several knobs, and I don't know if Qt and JDK set them all
> the same way.
>
>
>> I found native code that works with freetype and changed glyph loading
>> flags to the same as Qt has (i debugged it too), but they became even
>> unglier.
>>
>
> That doesn't add up.
>
>> Phil, why pisces isn't appropriate for B&W or LCD text? Just
>> interesting...
>>
>
> its a grey-scale antialiasing rasteriser, not  blitting code for already
> prepared images
> and grey-scale != B&W and grey-scale != LCD.
>
>> Point me please to right direction - to make Java font rendering
>> closer to Qt's should I learn pisces and compare it to Qt's rendering
>> or should I debug freetype invocations?
>>
>
> Probably look at the flags passed to freetype in each case. Revisit what
> those glyph
> loading flags are.
>
> -phil.
>
>> Attachments:
>> snapshot11 - tiny java app with DejaVu Sans Mono, Plain, 12 size font.
>> snapshot12 - the same font of size 10 in KWrite.
>> I assume that size (and roundness) difference is because of 72 DPI in
>> Java and 96 in KDE, but difference in antialiasing is obvious.
>>
>> On 5/16/10, Phil Race<philip.race at oracle.com>  wrote:
>>
>>> Expanding a little on Roman's comments :
>>>
>>> freetype is a font scaler or rasteriser. eg It takes a TrueType font and
>>> returns to
>>> its requester a bitmap or greymap image, or a path describing the glyph
>>> shape.
>>> Its role does not extend to rendering (ie putting the results of
>>> rasterisation
>>> on a surface). This isn't an "openjdk thing". Its just that's the role
>>> of freetype.
>>> Yes it also obtains the metrics in most cases.
>>>
>>> As Roman says there are specialised blitting routines for the text,
>>> including
>>> OpenGL pixel shader code, if that pipeline is optionally available and
>>> enabled.
>>>
>>>
>>> pisces isn't ever going to be the best (notably not the fastest) way to
>>> get text
>>> on screen and isn't appropriate for B&W or LCD text.
>>>
>>> -phil.
>>>
>>> Roman Kennke wrote:
>>>
>>>> Hello,
>>>>
>>>>
>>>>
>>>>> I want to hack into the sources of font rendering of openjdk, and I'm
>>>>> a bit confused now. So help me please understand how it works. Links
>>>>> are appreciated too.
>>>>>
>>>>> I read that freetype is used for fonts scaling, but after debugging it
>>>>> looks like freetype is used only to get font metrics, while real
>>>>> rendering is done using Pisces. I know nothing about real font
>>>>> rendering, so I have few questions about it:
>>>>> 1. am I right that freetype is used only to get font shapes while all
>>>>> rendering and antialiasing is done using Pisces?
>>>>>
>>>>>
>>>> No, not really. The Java2D stack also gets the rendered glyphs from
>>>> Freetype as bitmaps. These are displayed by pisces similar to images.
>>>>
>>>>
>>>>
>>>>> 2. isn't freetype can be used for font rendering and is used in GTK
>>>>> and Qt? Or freetype is only scaler?
>>>>>
>>>>>
>>>> There's the interface FontScaler in the sources (search for it). If you
>>>> manage to implement this using GTK or Qt... AFAIK, GTK and Qt use
>>>> Freetype themselves, so there wouldn't be any significant improvement.
>>>> Plus, the FontScaler interface is quite low level, I guess you'd have a
>>>> hard time implementing this using GTK or Qt, which are somwhat
>>>> higher-level.
>>>>
>>>>
>>>>
>>>>> 3. if freetype can be used for font rendering - why Pisces is used?
>>>>>
>>>>>
>>>> See above. Freetype does the actual rendering (anti-aliasing and such),
>>>> Pisces isn't really used, the resulting bitmaps are directly blitted to
>>>> the surface. Unless you're fetching the outlines and render them using
>>>> draw() or such, in this case freetype doesn't do the rendering. But
>>>> that's not the usual case.
>>>>
>>>>
>>>>
>>>>> 4th and the most important - how are you guys debugging native code?
>>>>> It's not supported with nbprojects, and I can't imagine how to launch
>>>>> java with some application to debug some native code...
>>>>>
>>>>>
>>>> I prefer to use gdb. You can launch Java this way:
>>>>
>>>> java -XX:OnError="gdb - %p" MyApplication
>>>>
>>>> this jumps into gdb whenever something bad happens.
>>>>
>>>> Kind regards, Roman