RFR: 8360136: RFE: Add TextAttributes for OpenType font figure style features

[Valery Semenchuk]

On Mon, 14 Jul 2025 13:43:40 GMT, Nikita Gubarkov <ngubarkov at openjdk.org> wrote:

>> @prrace about tests. I can draw test image with font which is support tnum feature, and validate without it. Primitive one.
>> 
>> For example
>>  * at start - need load font, which supports this features. For example `Inter` (also need attach license of it inside repo?)
>>  * draw image `0123456789` with `pnum` 
>>  * <img width="200" height="50" alt="pnum" src="https://github.com/user-attachments/assets/2e80a463-a608-425f-a264-6097e415d397" />
>>  * draw image `0123456789` with `tnum`
>>  * <img width="200" height="50" alt="tnum" src="https://github.com/user-attachments/assets/62600f4e-1094-4fce-bd09-3876b4a8610e" />
>>  * if all bytes of images equals - it's means `tnum` not works. 
>> 
>> Also check default instance of `Font` without options
>> 
>> We can add this images inside repo, and validate image drawing (not sure)
>
> @VISTALL You can take a look at https://github.com/openjdk/jdk/blob/bcd86d575fe0682a234228c18b0c2e817d3816da/test/jdk/java/awt/font/TextLayout/FormatCharAdvanceTest.java - it has a good example of synthetic font generated specifically for the test and embedded into the test as base64. This avoids the hussle with licences and whatnot.
> I would also suggest to avoid golden-image tests, as those tend to be burdensome to maintain. But in your case you can probably inspect line metrics and compare the widths of a sample text.

@YaaZ Thanks for example. About API. Will be good to make universal api - but I think it's too big task will be.

Maybe introduce api like nio2 - CopyOption* etc.

for example 


interface FontFeature<V> (FontExtension?) {
   // some code
}

// V is Integer? or delegate to impl
class OpenTypeFontFeature implements FontFeature<Integer > {
   OpenTypeFontFeature (String name) {
   }
}

public final class OpenTypeFontFeatures {
    FontFeature<Integer> TNUM = new OpenTypeFontFeature ("tnum");
} 



There few questions:
  * conflicting features?
  * need method `Font#supportsFeature(FontFeature)` ?
  * need opentype class? or utilize to default font naming? (get FontFeatureImpl)
  * need make public `OpenTypeFontFeature` class? (accesing from clients)
  * FontFeature can extend TextAttribute?

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PR Comment: https://git.openjdk.org/jdk/pull/26144#issuecomment-3069742252