Is it possible to detect how many OpenType stylistic sets a font has in code?

Two files in the Illustrator SDK look relevant to your interests, courtesy of a third-party repo that posted it (Adobe’s own developer page isn’t working in my Firefox):

https://github.com/WestonThayer/Bloks/blob/master/BloksAIPlugin/Vendor/illustratorapi/ate/ATESuites.h

The CharFeaturesSuite has functions for querying and setting OT features on a range of text in a text frame. (Look for the phrase “OpenType feature”.) I expect JSX’s CharacterAttributes.stylisticSets uses that under the hood.

https://github.com/WestonThayer/Bloks/blob/master/BloksAIPlugin/Vendor/illustratorapi/illustrator/AIFont.h

AIFontSuite’s functions provides a lot more font information  than JSX’s painfully limited TextFont class. (Look for “glyph set”.)

See if there’s anything there that whets your appetite. You’ll need a C/C++ developer to make use of it if you don’t know C yourself; there’s a few around these forums, typically under the SDK tag.

@Eduard Buta That's a good question... I couldn't work out how to find that out. As you discovered, if you set a stylistic set that the font doesn't have, it will set just fine, no error. You could potentially analyse the text metrics after the change to see if that particular text changed and that would prove that the stylistic set did exist in the font—but I can't imagine that would help in almost any real case. Sorry, I'm not much help.

- Mark

P.S. While I'm here, I'll just check that you understand an unusual feature of setting and getting `characterAttributes.stylisticSets`: that they take a "binary coded decimal", not a normal decimal. I've written a couple of functions to set and get stylistic sets. If you already know that, then you can ignore from here on. 🙂

You can use this to SET:

/**
 * Sets which stylistic sets are active on selected text.
 * Works with Indesign and Illustrator.
 */
(function () {

    // example usage: let's say we want to turn on stylistic sets 1, 2 and 5.
    setStylisticSets(app.activeDocument.selection, [1, 2, 5, 6]); // note: one-based indexing here

})();

/**
 * Set active Opentype stylistic sets.
 * @author m1b
 * @version 2022-12-24
 * @param {TextFrame|TextRange} text - the text.
 * @param {Array<Number>} stylisticSetIndices - indices of the stylistic sets to activate.
 */
function setStylisticSets(text, stylisticSetIndices) {

    if (
        text.constructor.name == 'Array'
        && text.length > 0
    )
        text = text[0];

    if (text.hasOwnProperty('textRange'))
        text = text.textRange;

    else if (text.hasOwnProperty('texts'))
        text = text.texts[0];

    if (app.name.search(/indesign/i) == -1)
        // convert to zero-based indexing
        for (var i = 0; i < stylisticSetIndices.length; i++)
            stylisticSetIndices[i]--;

    if (text.hasOwnProperty('characterAttributes'))
        text.characterAttributes.stylisticSets = getBinaryCodedDecimalForArray(stylisticSetIndices);

    else if (text.hasOwnProperty('otfStylisticSets'))
        text.otfStylisticSets = getBinaryCodedDecimalForArray(stylisticSetIndices);

    else {
        alert('Please select some text and try again.');
        return;
    }

};

/**
 * Returns a binary coded decimal number (BCD)
 * representing binary bits.
 *
 * Use case: in Indesign and Illustrator,
 * `characterAttributes.stylisticSets`
 * are stored as a BCD.
 *
 * Example 1:
 *   - for Opentype stylistic sets 1 and 5:
 *   - `numbers` array = [0,4]
 *   - returns 17 (10001 in binary).
 *
 * Example 2:
 *   - for opentype stylistic sets 3, 4 and 5:
 *   - `numbers` array = [2,3,4]
 *   - returns 28 (11100 in binary).
 *
 * @author m1b
 * @version 2023-07-12
 * @param {Array<Number>} numbers - the stylistic sets indices, eg. [2,4,5].
 * @returns {Number} - the decimal number representing the numbers.
 */
function getBinaryCodedDecimalForArray(numbers) {

    var arr = numbers.slice().sort(),
        bin = [],
        len = arr[arr.length - 1],
        i = len + 1,
        val = arr.pop();

    while (i--) {

        if (val == i) {
            bin[len - i] = 1;
            val = arr.pop();
        }

        else {
            bin[len - i] = 0;
        }

    }

    // join into binary number and parse binary as decimal
    return parseInt(bin.join(''), 2);

};

And use this to GET:

/**
 * Reads which stylistic sets are active given selected text.
 */
(function () {

    var flags = getActiveStylisticSetsForIllustrator(app.activeDocument.selection);

    if (flags) {

        // just for demonstrating:
        for (var i = flags.length - 1; i >= 0; i--)
            if (flags[i] == true)
                $.writeln('Stylistic Set ' + (flags.length - i) + ' is active.');

    }

})();

/**
 * Returns an array of booleans representing
 * active opentype stylistic sets.
 * Note: will only return results of stylistic
 * sets applied to the first character of `text`.
 * @author m1b
 * @version 2023-10-18
 * @param {TextRange} text - the text to test.
 * @returns {Array<Boolean>}
 */
function getActiveStylisticSetsForIllustrator(text) {

    var setsNumber;

    if (text.constructor.name == 'Array')
        text = text[0];

    if (text.constructor.name == 'TextFrame')
        text = text.textRange;

    if (text.hasOwnProperty('stylisticSets'))
        setsNumber = text.stylisticSets;

    else if (text.hasOwnProperty('characterAttributes'))
        setsNumber = text.characterAttributes.stylisticSets;

    if (setsNumber != undefined)
        return getNumberAsBits(setsNumber);

};

/**
 * Convert a decimal number into an array of
 * boolean values for each binary place.
 * For example:
 * for n: 2 -> [true, false].
 * for n: 37 -> [true, false, false, true, false, true].
 * @author m1b
 * @version 2023-10-18
 * @param {Number} n - a decimal number.
 * @returns {Array<Boolean>} - n as binary number represented by array of booleans.
 */
function getNumberAsBits(n) {

    var bits = [],
        b = (n).toString(2);

    for (var i = 0; i < b.length; i++)
        bits[i] = b[i] == '1';

    return bits

};

/**
 * Returns a binary coded decimal number (BCD)
 * representing binary bits.
 * 
 * Use case: in Indesign and Illustrator,
 * `characterAttributes.stylisticSets`
 * are stored as a BCD.
 * 
 * Example 1:
 *   - for Opentype stylistic sets 1 and 5:
 *   - `numbers` array = [0,4]
 *   - returns 17 (10001 in binary).
 * 
 * Example 2:
 *   - for opentype stylistic sets 3, 4 and 5:
 *   - `numbers` array = [2,3,4]
 *   - returns 28 (11100 in binary).
 * 
 * @author m1b
 * @version 2023-07-12
 * @param {Array<Number>} numbers - the stylistic sets indices, eg. [2,4,5].
 * @returns {Number} - the decimal number representing the numbers.
 */
function getBinaryCodedDecimalForArray(numbers) {

    var arr = numbers.slice().sort(),
        bin = [],
        len = arr[arr.length - 1],
        i = len + 1,
        val = arr.pop();

    while (i--) {

        if (val == i) {
            bin[len - i] = 1;
            val = arr.pop();
        }

        else {
            bin[len - i] = 0;
        }

    }

    // join into binary number and parse binary as decimal
    return parseInt(bin.join(''), 2);

};

Edit 2024-08-20: removed unused function.