Dashboard/Dashboard.Media.Defaults/FontDatabaseProvider.cs

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using ReFuel.FreeType;
using Dashboard.Media.Defaults.Fallback;
using Dashboard.Media.Defaults.Linux;
using Dashboard.Media.Font;
using Dashboard.PAL;

namespace Dashboard.Media.Defaults
{
    public static class FontDataBaseProvider
    {
        public static IFontDataBase Instance { get; }

        static FontDataBaseProvider()
        {
            try
            {
                // TODO: add as other operating systems are supported.
                if (OperatingSystem.IsLinux())
                {
                    Instance = new FontConfigFontDatabase();
                }
                else
                {
                    Instance = new FallbackFontDatabase();
                }
            }
            catch (Exception ex)
            {
                throw new NotSupportedException("Could not load a suitable font database implementation.", ex);
            }
        }

        public static (FontFace, FileInfo) ResolveSystemFont(string envVar, string defaults, IFontDataBase db)
        {
            StringBuilder builder = new StringBuilder();

            string user = Environment.GetEnvironmentVariable(envVar);
            if (user != null)
            {
                builder.Append(user);
                builder.Append(':');
            }

            builder.Append(defaults);

            string[] list = builder.ToString().Split(':');

            foreach (string item in list)
            {
                if (File.Exists(item))
                {
                    // Process file.
                    if (FT.NewFace(FTProvider.Ft, item, 0, out FTFace ftface) != FTError.None)
                    {
                        continue;
                    }

                    FontFace face = FontFace.Parse(ftface.FamilyName, ftface.StyleName);
                    FT.DoneFace(ftface);

                    return (face, new FileInfo(item));
                }
                else
                {
                    IEnumerable<FontFace> faces = db.Search(
                        new FontFace(item, FontSlant.Normal, FontWeight.Normal, FontStretch.Normal),
                        FontMatchCriteria.Family);

                    if (faces.Any())
                    {
                        FontFace face = faces.First();
                        return (face, db.FontFileInfo(face));
                    }
                }
            }

            try
            {
                FontFace face = db.GetSystemFontFace(SystemFontFamily.Sans);
                return (face, db.FontFileInfo(face));
            }
            catch (Exception ex)
            {
                throw new NotImplementedException("No fallback font yet.", ex);
            }
        }
    }
}