How to use TextAnalyzer.GetTypographicFeatures method

Question

I need to get the available OpenType features for a given font in my app (C#). I'm using DirectWrite through SharpDX and I'm having a really bad time.

I know that the best solution is to use this method:

SharpDX.DirectWrite.TextAnalyzer2.GetTypographicFeatures

but I don't know how to get a result from it, as I don't know where to get the parameters.

These are the parameters I need to provide in order to get the Font Features:

1. fontFace FontFace
2. scriptAnalysis ScriptAnalysis
3. localName String
4. maxTagCount int
5. actualTagCount int
6. tags FontFeatureTag

Can someone please provide me a better explanation or (ideally) some code. There is almost no documentation about it so I don't know where I can get these parameters and/or what they mean.

Thanks in advance.

Answer 1

I figure it out lastly. Thanks to Buglehead who gave me the final piece of the puzzle.

Here is an example. In this code I first load all system fonts, then get a specific font, and then get the FontFeatureTags for that specific font.

using SharpDX.DirectWrite;

private void LoadFontFeatureTags()
{
    Factory f = new Factory(FactoryType.Isolated);
    Factory4 _factory = new Factory4(f.NativePointer);
    _factory.CreateFontCollectionFromFontSet(_factory.SystemFontSet, out FontCollection1 collection);
    List<SharpDX.DirectWrite.FontFamily> loadedFonts = new List<SharpDX.DirectWrite.FontFamily>();
    for (int i = 0; i < collection.FontFamilyCount; i++)
    {
        var family = collection.GetFontFamily(i);
        loadedFonts.Add(family);
    }
    var gabriolaFont = loadedFonts.FirstOrDefault(x => x.FamilyNames.GetString(0).Contains("Gabriola"));
    var gabriolaFirstChild = gabriolaFont.GetFont(0);
    Font3 f3 = new Font3(gabriolaFirstChild.NativePointer);
    f3.CreateFontFace(out FontFace3 face3);

    ScriptAnalysis analysis = new ScriptAnalysis();
    TextAnalyzer analyzer = new TextAnalyzer(f);
    TextAnalyzer2 analyzer2 = new TextAnalyzer2((IntPtr)analyzer);
    int maxTagCount = 32;
    FontFeatureTag[] featuresArray = new FontFeatureTag[maxTagCount];
    analyzer2.GetTypographicFeatures(face3, analysis, "es-US", maxTagCount, out int actualCount, featuresArray);
}