Dashboard/Dashboard.Media.Defaults/Linux/FontConfig.cs

using System;
using System.Runtime.InteropServices;
using System.Runtime.CompilerServices;
using System.Text;
using Dashboard;

namespace Dashboard.Media.Defaults
{
    public static unsafe class FontConfig
    {
        private const string fontconfig = "fontconfig";

        public static bool Exists { get; }

        public static IntPtr FAMILY { get; } = Marshal.StringToHGlobalAnsi("family");
        public static IntPtr STYLE { get; } = Marshal.StringToHGlobalAnsi("style");
        public static IntPtr FILE { get; } = Marshal.StringToHGlobalAnsi("file");
        public static IntPtr WEIGHT { get; } = Marshal.StringToHGlobalAnsi("weight");
        public static IntPtr SLANT { get; } = Marshal.StringToHGlobalAnsi("slant");


        static FontConfig()
        {
            try
            {
                if (FcInitLoadConfigAndFonts() == null)
                {
                    Exists = false;
                }
                Exists = true;
            }
            catch
            {
                Exists = false;
            }
        }

        [DllImport(fontconfig, EntryPoint = "FcInitLoadConfigAndFonts")]
        public static extern FcConfig* FcInitLoadConfigAndFonts();

        [DllImport(fontconfig, EntryPoint = "FcConfigGetCurrent")]
        public static extern FcConfig ConfigGetCurrent();

        [DllImport(fontconfig, EntryPoint = "FcPatternCreate")]
        public static extern FcPattern PatternCreate();

        [DllImport(fontconfig, EntryPoint = "FcPatternCreate")]
        public static extern bool FcPatternAdd(FcPattern pattern, IntPtr what, FcValue value, bool append);

        [DllImport(fontconfig, EntryPoint = "FcObjectSetBuild", CallingConvention = CallingConvention.Cdecl)]
        public static extern FcObjectSet ObjectSetBuild(IntPtr i1, IntPtr i2, IntPtr i3, IntPtr i4, IntPtr i5, IntPtr i6);

        public static FcObjectSet ObjectSetBuild(IntPtr i1)
        {
            return ObjectSetBuild(i1, IntPtr.Zero);
        }

        public static FcObjectSet ObjectSetBuild(IntPtr i1, IntPtr i2)
        {
            return ObjectSetBuild(i1, i2, IntPtr.Zero);
        }
        public static FcObjectSet ObjectSetBuild(IntPtr i1, IntPtr i2, IntPtr i3)
        {
            return ObjectSetBuild(i1, i2, i3, IntPtr.Zero);
        }
        public static FcObjectSet ObjectSetBuild(IntPtr i1, IntPtr i2, IntPtr i3, IntPtr i4)
        {
            return ObjectSetBuild(i1, i2, i3, i4, IntPtr.Zero);
        }
        public static FcObjectSet ObjectSetBuild(IntPtr i1, IntPtr i2, IntPtr i3, IntPtr i4, IntPtr i5)
        {
            return ObjectSetBuild(i1, i2, i3, i4, i5, IntPtr.Zero);
        }

        [DllImport(fontconfig, EntryPoint = "FcFontList")]
        public static extern FcFontSet FontList(FcConfig config, FcPattern pattern, FcObjectSet objectSet);

        [DllImport(fontconfig, EntryPoint = "FcNameUnparse")]
        public static extern IntPtr NameUnparse(FcPattern pat);

        public static string NameUnparseStr(FcPattern pat) => Marshal.PtrToStringAnsi(NameUnparse(pat));

        [DllImport(fontconfig, EntryPoint = "FcPatternGetString")]
        public static extern FcResult PatternGetString(FcPattern p, IntPtr what, int n, out IntPtr val);

        public static FcResult PatternGetString(FcPattern p, IntPtr what, out string str)
        {
            FcResult i = PatternGetString(p, what, 0, out IntPtr ptr);

            if (i == FcResult.Match)
            {
                str = Marshal.PtrToStringAnsi(ptr);
            }
            else
            {
                str = null;
            }

            Marshal.FreeHGlobal(ptr);

            return i;
        }

        [DllImport(fontconfig, EntryPoint = "FcPatternGet")]
        public static extern FcResult PatternGet(FcPattern p, IntPtr what, int id, out FcValue value);

        [DllImport(fontconfig, EntryPoint = "FcFontSetDestroy")]
        public static extern void FontSetDestroy(FcFontSet fs);

        [DllImport(fontconfig, EntryPoint = "FcObjectSetDestroy")]
        public static extern void ObjectSetDestroy (FcObjectSet os);

        [DllImport(fontconfig, EntryPoint = "FcConfigDestroy")]
        public static extern void ConfigDestroy (FcConfig cfg);

        [DllImport(fontconfig, EntryPoint = "FcPatternDestroy")]
        public static extern void PatternDestroy (FcPattern os);

        #region Range

        [DllImport(fontconfig, EntryPoint = "FcRangeCreateDouble")]
        public static extern IntPtr RangeCreateDouble(double begin, double end);

        [DllImport(fontconfig, EntryPoint = "FcRangeCreateInteger")]
        public static extern IntPtr RangeCreateInteger (int begin, int end);

        [DllImport(fontconfig, EntryPoint = "FcRangeDestroy")]
        public static extern void RangeDestroy(IntPtr range);

        [DllImport(fontconfig, EntryPoint = "FcRangeCopy")]
        public static extern IntPtr RangeCopy (IntPtr range);

        [DllImport(fontconfig, EntryPoint = "FcRangeGetDouble")]
        public static extern bool RangeGetDouble(IntPtr range, out double start, out double end);

        #endregion
    }

    public enum FcResult
    {
        Match,
        NoMatch,
        TypeMismatch,
        NoId,
        OutOfMemory
    }

    public struct FcConfig
    {
        public readonly IntPtr Handle;
    }

    public struct FcPattern
    {
        public readonly IntPtr Handle;
    }

    public unsafe struct FcObjectSet
    {
        public readonly IntPtr Handle;

        private Accessor* AsPtr => (Accessor*)Handle;

        public int NObject => AsPtr->nobject;

        public int SObject => AsPtr->sobject;

        #pragma warning disable CS0649 // Will always have default value.
        private struct Accessor
        {
            public int nobject;
            public int sobject;
            public byte** objects;
        }
        #pragma warning restore CS0649
    }

    public unsafe struct FcFontSet
    {
        public readonly IntPtr Handle;
        private Accessor* AsPtr => (Accessor*)Handle;

        public int NFont => AsPtr->nfont;
        public int SFont => AsPtr->sfont;

        public FcPattern this[int i]
        {
            get
            {
                if (i < 0 || i >= NFont)
                    throw new IndexOutOfRangeException();

                return AsPtr->fonts[i];
            }
        }

        #pragma warning disable CS0649 // Will always have default value.
        private struct Accessor
        {
            public int nfont;
            public int sfont;
            public FcPattern* fonts;
        }
        #pragma warning restore CS0649
    }

    public enum FcType
    {
        Unknown = -1,
        Void,
        Integer,
        Double,
        String,
        Bool,
        Matrix,
        CharSet,
        FTFace,
        LangSet,
        Range
    }

    [StructLayout(LayoutKind.Explicit)]
    public readonly struct FcValue
    {
        [FieldOffset(0)] public readonly FcType Type;
        [FieldOffset(sizeof(FcType))] public readonly IntPtr Pointer;
        [FieldOffset(sizeof(FcType))] public readonly int Int;
        [FieldOffset(sizeof(FcType))] public readonly double Double;
    }
}