engine: render immediate text into surfaces

2026-07-30 18:47:35 -04:00
parent 6a8c919df1
commit c2b72cd4b9
9 changed files with 563 additions and 22 deletions
--- a/engine/Age.Engine/Text/ImmediateSurfaceTextRenderer.cs
+++ b/engine/Age.Engine/Text/ImmediateSurfaceTextRenderer.cs
@@ -0,0 +1,103 @@
+using System.Text;
+using Age.Engine.Model;
+using Age.Engine.Sys4;
+
+namespace Age.Engine.Text;
+
+public readonly record struct ImmediateSurfaceTextResult(
+    int GlyphCount,
+    int CursorX,
+    int CursorY);
+
+/// <summary>
+/// Converts one native CP932 string into exact glyph requests and composites it directly into an
+/// AGE RGBA surface. Request construction completes before any pixels change, so an unsupported
+/// character cannot leave a partially drawn string behind.
+/// </summary>
+public sealed class ImmediateSurfaceTextRenderer
+{
+    public const string DefaultFontFace = "ＭＳ 明朝";
+
+    private static readonly Encoding Cp932 = CreateCp932();
+    private readonly IGlyphMaskRasterizer _rasterizer;
+
+    public ImmediateSurfaceTextRenderer(IGlyphMaskRasterizer rasterizer)
+        => _rasterizer = rasterizer ?? throw new ArgumentNullException(nameof(rasterizer));
+
+    public ImmediateSurfaceTextResult Render(
+        RgbaImage destination,
+        int x,
+        int y,
+        string text,
+        AdvTextStyle style)
+    {
+        ArgumentNullException.ThrowIfNull(destination);
+        ArgumentNullException.ThrowIfNull(text);
+        IReadOnlyList<GlyphRasterRequest> requests = CreateRequests(text, style);
+        int cursorX = x;
+        int cursorY = y;
+        foreach (GlyphRasterRequest request in requests)
+        {
+            GlyphMask mask = _rasterizer.Rasterize(request);
+            AgeGlyphMaskCompositor.DrawGlyph(
+                destination, mask, cursorX, cursorY, request.PixelHeight, style);
+            cursorX = checked(cursorX + mask.CellAdvanceX);
+            cursorY = checked(cursorY + mask.CellAdvanceY);
+        }
+        return new ImmediateSurfaceTextResult(requests.Count, cursorX, cursorY);
+    }
+
+    public static IReadOnlyList<GlyphRasterRequest> CreateRequests(
+        string text,
+        AdvTextStyle style)
+    {
+        ArgumentNullException.ThrowIfNull(text);
+        int requestedHeight = style.PrimaryFontSize > 0 ? style.PrimaryFontSize : 24;
+        int pixelHeight = NativePixelHeight(requestedHeight);
+        int requestedWidth = -(pixelHeight / 2);
+        int weight = style.Bold ? 700 : 0;
+        string fontFace = string.IsNullOrWhiteSpace(style.FontFace)
+            ? DefaultFontFace
+            : style.FontFace;
+        var requests = new List<GlyphRasterRequest>(text.Length);
+
+        foreach (Rune rune in text.EnumerateRunes())
+        {
+            byte[] encoded;
+            try
+            {
+                encoded = Cp932.GetBytes(rune.ToString());
+            }
+            catch (EncoderFallbackException error)
+            {
+                throw new ArgumentException(
+                    $"U+{rune.Value:X4} is not representable in native CP932 text.", nameof(text), error);
+            }
+            if (encoded.Length is < 1 or > 2)
+                throw new ArgumentException(
+                    $"U+{rune.Value:X4} encoded to unsupported CP932 length {encoded.Length}.",
+                    nameof(text));
+            ushort cp932Code = encoded.Length == 1
+                ? encoded[0]
+                : (ushort)((encoded[0] << 8) | encoded[1]);
+            requests.Add(new GlyphRasterRequest(
+                fontFace, pixelHeight, requestedWidth, weight,
+                rune.Value, cp932Code, GlyphRasterPolicy.NativeCp932Gray4));
+        }
+        return requests;
+    }
+
+    public static int NativePixelHeight(int requestedHeight)
+    {
+        if (requestedHeight <= 0) return 24;
+        if (requestedHeight is 32 or 33) return 31;
+        return (requestedHeight & 1) != 0 ? requestedHeight - 1 : requestedHeight;
+    }
+
+    private static Encoding CreateCp932()
+    {
+        Encoding.RegisterProvider(CodePagesEncodingProvider.Instance);
+        return Encoding.GetEncoding(
+            932, EncoderFallback.ExceptionFallback, DecoderFallback.ExceptionFallback);
+    }
+}