engine: complete portable glyph text backend
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gamer147
180
godot/GodotTextServerGlyphMaskRasterizer.cs
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180
godot/GodotTextServerGlyphMaskRasterizer.cs
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using System;
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using Age.Engine.Text;
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using Godot;
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/// <summary>
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/// Portable, explicitly non-pixel-exact glyph masks obtained from Godot's TextServer atlas.
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/// AGE still owns layout, effects, blending, retained ordering, and surface lifetime.
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/// </summary>
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public sealed class GodotTextServerGlyphMaskRasterizer :
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IIdentifiedGlyphMaskRasterizer, IDisposable
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{
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private readonly record struct FontKey(string RequestedFace, int Weight);
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private readonly object _gate = new();
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private readonly PortableTextRenderingPolicy _policy;
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private readonly TextServer _textServer;
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private readonly BoundedLruCache<FontKey, SystemFont> _fonts;
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private bool _disposed;
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public GodotTextServerGlyphMaskRasterizer(PortableTextRenderingPolicy policy)
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{
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_policy = policy ?? throw new ArgumentNullException(nameof(policy));
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_textServer = TextServerManager.GetPrimaryInterface()
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?? throw new InvalidOperationException("Godot has no primary TextServer interface.");
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_fonts = new BoundedLruCache<FontKey, SystemFont>(
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policy.FontCacheCapacity, font => font.Dispose());
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BackendInfo = new GlyphRasterizerBackendInfo(
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"portable-godot-textserver",
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"Godot TextServer system fonts",
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GlyphRasterPolicy.PortableUnicode,
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NativePixelExact: false,
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$"policy={policy.Id}; raster={policy.Raster.Antialiasing}/" +
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$"{policy.Raster.Hinting}/{policy.Raster.SubpixelPositioning}; " +
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"Unicode system-font substitution; not GDI pixel-exact");
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}
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public GlyphRasterizerBackendInfo BackendInfo { get; }
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public GlyphMask Rasterize(GlyphRasterRequest request)
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{
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ArgumentNullException.ThrowIfNull(request);
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if (request.Policy != GlyphRasterPolicy.PortableUnicode)
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throw new ArgumentException(
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"Godot TextServer accepts only portable Unicode glyph requests.",
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nameof(request));
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lock (_gate)
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{
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ObjectDisposedException.ThrowIf(_disposed, this);
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SystemFont font = ResolveFont(request);
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// Asking the high-level Font for the character primes both the selected system face
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// and any system fallback RID before we inspect the TextServer cache directly.
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_ = font.GetCharSize(request.UnicodeScalar, request.PixelHeight);
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Rid rid = FindGlyphRid(font, request);
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long glyph = _textServer.FontGetGlyphIndex(
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rid, request.PixelHeight, request.UnicodeScalar, 0);
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if (glyph == 0 && request.UnicodeScalar != 0)
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throw MissingGlyph(request);
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var sizeKey = new Vector2I(request.PixelHeight, 0);
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_textServer.FontRenderGlyph(rid, sizeKey, glyph);
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Vector2 glyphSize = _textServer.FontGetGlyphSize(rid, sizeKey, glyph);
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Vector2 glyphOffset = _textServer.FontGetGlyphOffset(rid, sizeKey, glyph);
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Vector2 advance = _textServer.FontGetGlyphAdvance(
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rid, request.PixelHeight, glyph);
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Rect2 uv = _textServer.FontGetGlyphUVRect(rid, sizeKey, glyph);
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int width = Math.Max(0, Mathf.RoundToInt(glyphSize.X));
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int height = Math.Max(0, Mathf.RoundToInt(glyphSize.Y));
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byte[] coverage = width == 0 || height == 0
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? []
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: ExtractCoverage(rid, sizeKey, glyph, uv, width, height);
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int advanceX = Mathf.RoundToInt(advance.X);
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return new GlyphMask(
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width,
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height,
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width,
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Mathf.RoundToInt(glyphOffset.X),
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-Mathf.RoundToInt(glyphOffset.Y),
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advanceX,
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0,
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Math.Max(width, advanceX),
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request.PixelHeight,
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coverage);
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}
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}
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public void Dispose()
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{
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lock (_gate)
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{
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if (_disposed) return;
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_disposed = true;
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_fonts.Clear();
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}
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}
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private SystemFont ResolveFont(GlyphRasterRequest request)
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{
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PortableFontRasterPolicy raster = _policy.Raster;
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int weight = request.Weight >= raster.BoldThreshold
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? raster.BoldWeight
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: raster.RegularWeight;
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var key = new FontKey(request.FontFace, weight);
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if (_fonts.TryGetValue(key, out SystemFont? cached)) return cached;
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var font = new SystemFont
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{
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FontNames = _policy.ResolveFamilies(request.FontFace),
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FontWeight = weight,
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AllowSystemFallback = raster.AllowSystemFallback,
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Antialiasing = raster.Antialiasing switch
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{
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"none" => TextServer.FontAntialiasing.None,
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"lcd" => TextServer.FontAntialiasing.Lcd,
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_ => TextServer.FontAntialiasing.Gray,
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},
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Hinting = raster.Hinting switch
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{
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"none" => TextServer.Hinting.None,
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"light" => TextServer.Hinting.Light,
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_ => TextServer.Hinting.Normal,
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},
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SubpixelPositioning = raster.SubpixelPositioning switch
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{
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"auto" => TextServer.SubpixelPositioning.Auto,
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"one-half" => TextServer.SubpixelPositioning.OneHalf,
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"one-quarter" => TextServer.SubpixelPositioning.OneQuarter,
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_ => TextServer.SubpixelPositioning.Disabled,
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},
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MultichannelSignedDistanceField =
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raster.MultichannelSignedDistanceField,
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};
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_fonts.Set(key, font);
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return font;
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}
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private Rid FindGlyphRid(SystemFont font, GlyphRasterRequest request)
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{
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foreach (Rid rid in font.GetRids())
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if (_textServer.FontHasChar(rid, request.UnicodeScalar))
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return rid;
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throw MissingGlyph(request);
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}
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private byte[] ExtractCoverage(
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Rid rid,
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Vector2I sizeKey,
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long glyph,
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Rect2 uv,
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int width,
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int height)
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{
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long textureIndex = _textServer.FontGetGlyphTextureIdx(rid, sizeKey, glyph);
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Image atlas = _textServer.FontGetTextureImage(rid, sizeKey, textureIndex)
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?? throw new InvalidOperationException("TextServer returned no glyph atlas image.");
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int left = Mathf.RoundToInt(uv.Position.X);
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int top = Mathf.RoundToInt(uv.Position.Y);
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var result = new byte[checked(width * height)];
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for (int y = 0; y < height; y++)
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for (int x = 0; x < width; x++)
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{
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Color pixel = atlas.GetPixel(left + x, top + y);
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float mask = atlas.GetFormat() switch
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{
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Image.Format.L8 => pixel.R,
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Image.Format.Rgb8 => Math.Max(pixel.R, Math.Max(pixel.G, pixel.B)),
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_ => pixel.A,
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};
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result[y * width + x] =
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(byte)Math.Clamp(Mathf.RoundToInt(mask * 16f), 0, 16);
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}
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return result;
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}
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private static Exception MissingGlyph(GlyphRasterRequest request)
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=> new InvalidOperationException(
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$"Portable font policy could not resolve U+{request.UnicodeScalar:X4} " +
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$"for authored face '{request.FontFace}'.");
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}
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