Feedback request: Add new RenderingHints.KEY_FONT_HINTING

[Daniel Gredler]

Hi Phil,

Thank you for the response and the insights!

I have to admit I don't know much about the situation in macOS, but I
assume they're moving things in a direction that works best for their
particular situation (complete control over both the software and hardware
stacks, and best-in-class displays).

I have indeed experimented with VALUE_TEXT_ANTIALIAS_GASP, and I have two
problems with this "font knows best" approach:

1. You're not actually trusting the font to know best. For example, the
Google Noto Sans Condensed Bold "gasp" table contains a single entry
indicating that grid-fitting (i.e. hinting) and grayscale rendering (i.e.
anti-aliasing) should both always be used, at all sizes. However, when I
use this font in Java with VALUE_TEXT_ANTIALIAS_GASP and
VALUE_FRACTIONALMETRICS_ON, Java correctly trusts the font regarding AA and
enables it, but then ignores the font regarding hinting (because currently
AA + FM = no hinting, and everything else is hinted, regardless of what
"gasp" says).

2. The font doesn't actually always know best. The application developer
knows whether they are creating documents to be printed (and if so, whether
they are intended to be printed on low-DPI or high-DPI devices), whether
they are creating a desktop application with text animation and scaling
(like a dynamic reporting dashboard or a videogame), whether they are
creating a desktop application with static text (like a PDF viewer), etc.
The developer may want to use one font for all of these use cases, but with
different rendering hints.

Interestingly, in addition to the three key values that I had proposed
(VALUE_FONT_HINTING_DEFAULT, VALUE_FONT_HINTING_ON,
VALUE_FONT_HINTING_OFF), I had actually considered a fourth:
VALUE_FONT_HINTING_GASP. I didn't include it originally because I think the
direct control over font hinting is most valuable, but it does make for a
nice parallel with VALUE_TEXT_ANTIALIAS_GASP, and the combination would
enable a real "font knows best" mode.

Let me know what you think about these two points and the idea of a fourth
hinting option.

Take care,

Daniel



On Mon, Jul 15, 2024 at 9:22 PM Philip Race <philip.race at oracle.com> wrote:

>
>
> Platforms are tending towards AA+unhinted - this is all we can get from
> macOS today so I'm not sure how well we could support this hint.
>
> And being able to turn off hinting when doing modes such as B&W is
> unlikely to produce good results on any font you'd want to use.
>
> Have you looked at the existing VALUE_TEXT_ANTIALIAS_GASP hint ?
>
>
> https://docs.oracle.com/en/java/javase/21/docs/api/java.desktop/java/awt/RenderingHints.html#VALUE_TEXT_ANTIALIAS_GASP
>
> it uses the OpenType table
> https://learn.microsoft.com/en-us/typography/opentype/spec/gasp
> which basically tells the rasteriser at a specific size which
> combination of hinting and anti-aliasing to use.
>
> If apps use together with the FM hint they should get most of what they
> want.
> Where JDK can (this means when we use freetype) you'd get FM PLUS the
> appropriate AA PLUS the appropriate hinting choice
>
> I think this is better than a hint where an app will have to guess,
> probably wrongly.
>
> -phil.
>
>
> On 7/14/24 7:15 AM, Daniel Gredler wrote:
> > Hi all,
> >
> > We've had a bit of back-and-forth regarding whether font hinting is
> > enabled or disabled when drawing grayscale text with anti-aliasing and
> > fractional metrics enabled [1, 2]. Setting AA + FM disabled font
> > hinting in JDK 8 - 10, then JDK 11 changed this so that AA + FM would
> > *not* disable hinting, and finally the behavior was reverted in JDK 14
> > (and backported to JDK 11).
> >
> > Generalizing a bit, the current behavior (AA + FM disables hinting) is
> > optimal for "the desktop use case" (JavaFX, animations, smooth
> > scaling, etc). The JDK 11/12/13 behavior was optimal for "the backend
> > use case" (individual image creation, no animations).
> >
> > I think it would be useful to have a new java.awt.RenderingHints key
> > named RenderingHints.KEY_FONT_HINTING, with the following possible
> values:
> > - RenderingHints.VALUE_FONT_HINTING_DEFAULT: current behavior,
> > dictated by AA + FM
> > - RenderingHints.VALUE_FONT_HINTING_ON: enable font hinting,
> > regardless of AA + FM
> > - RenderingHints.VALUE_FONT_HINTING_OFF: disable font hinting,
> > regardless of AA + FM
> >
> > This new rendering hint would allow direct control over whether font
> > hinting is enabled or not, and would specifically enable the use of AA
> > + FM + font hints in Java.
> >
> > I'm happy to create a patch with this feature (I have a signed OCA on
> > file), but wanted to get feedback on the idea first. Let me know what
> > you think!
> >
> > Take care,
> >
> > Daniel
> >
> > [1] https://bugs.openjdk.org/browse/JDK-8214481
> > [2] https://bugs.openjdk.org/browse/JDK-8242285
> >
>
>
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