Lots of improvements (OTF fixes, more GPOS, synthetic bold/italics)

README.md

@@ -1,2 +1,46 @@
-# SafeStbTrueTypeSharp
-Safe version of StbTrueTypeSharp 1.24
+# ArtificialNecessity.Fonts
+
+**A C# Memory-Safe Font Engine — TTF, OTF, CPU Glyph Raster + simplified Kerning, Glyph-Shaping, and Advance.**
+
+This library descends from [SafeStbTrueTypeSharp](https://github.com/rds1983/SafeStbTrueTypeSharp) (rds1983's fully-safe C# port of stb_truetype 1.24). It contains zero `unsafe` code — all font data access goes through bounds-checked `FakePtr<byte>` views over managed arrays.
+
+## License
+
+MIT / Public-Domain, following stb_truetype and SafeStbTrueTypeSharp upstream.
+
+## What we changed since the fork
+
+Everything after upstream commit `2f76ecb` (2020) is ours:
+
+| Area | Summary |
+|---|---|
+| **OTF/CFF fixes** | Corrected CFF/CharString parsing bugs and multi-component (composite) glyph handling; added OTF test fonts. |
+| **Full GPOS pair kerning** | Replaced stb_truetype's minimal GPOS stub with a proper pair-kerning kernel: script/feature selection, Extension lookups, full ValueRecord layout, class-0 handling. Validated against a numeric HarfBuzz oracle (`tests/GposKerning.Tests`). |
+| **Y-only grid-fit raster** | `stbtt_YPixelGridFitRemap` entry points: a monotonic y-remap applied during rasterization for crisp horizontal stems (see SilkyNvg `plans/crisp_text_yonly_gridfit_hinting.md`) without touching x-spacing. |
+| **Synthetic styles** | Outline-preprocessing synthesis: fake-bold via stroke-union embolden, oblique shear, and horizontal scaling (`FontInfoSynth.cs`). |
+| **Hygiene** | Removed the dead upstream MonoGame sample; restructured `tests/` into per-project subdirectories. |
+
+## Scope of our attentions
+
+We care about **CPU glyph rasterization and simplified horizontal text layout** for UI-grade Latin-script text: glyph loading (TrueType `glyf` and OTF/CFF outlines), advance widths, pair kerning, and high-quality anti-aliased raster output. We are deliberately **not** a full text-shaping engine (no HarfBuzz-style contextual shaping, ligature substitution/GSUB, vertical layout, or complex-script support).
+
+## The GPOS kernel: capabilities and limitations
+
+`stbtt_GetGlyphKernAdvance` makes a **font-level** decision (never mixed per-pair): if the font's GPOS carries a usable `kern` feature it is used; otherwise we fall back to the legacy `kern` table (this also covers fonts whose GPOS exists but is mark/mkmk-only).
+
+### Capabilities
+
+- **Script/feature selection**: prefers the `latn` script, falls back to `DFLT`, uses the default LangSys. Marks the lookups of *every* `kern` feature in the LangSys, applies them in LookupList index order (OpenType application order), and **accumulates adjustments across lookups**. Resolution is cached once per font.
+- **Lookup types**: PairAdjustment (type 2), including type 9 Extension-wrapped subtables (32-bit offsets, as emitted by large fonts).
+- **Both PairPos formats**: format 1 (per-glyph pair lists, binary-searched) and format 2 (class matrices).
+- **Full ValueRecord layout**: record size computed from `popcount(valueFormat)`, including the device-table offset bits (0x0010–0x0080) that contribute to record *size*; `xAdvance` located correctly after XPlacement/YPlacement.
+- **HarfBuzz “applied” semantics**: within a lookup the *first subtable that applies* wins. Format 1 applies only when a pair record is found; format 2 applies whenever coverage hits and both classes resolve — *even when the adjustment is zero* (the class-0 fix). A coverage hit without a pair record correctly falls through to the next subtable.
+- **Oracle-tested**: `tests/GposKerning.Tests` compares our numeric results against HarfBuzz output for real fonts.
+
+### Limitations (deliberate)
+
+- **xAdvance of glyph 1 only.** We return a single horizontal advance adjustment; YAdvance, placements, and the second glyph's ValueRecord are ignored.
+- **Pair kerning only.** No mark attachment (types 4–6), cursive attachment (type 3), single adjustment (type 1), or contextual positioning (types 7–8).
+- **No device tables / variations.** Device-table and VariationIndex adjustments are skipped (their offsets are only counted for record sizing); values are unscaled font units.
+- **LookupFlags ignored.** For base-glyph pair kerning the only flag observed in target fonts is `IgnoreMarks` (0x0008), which is a no-op when neither glyph is a mark.
+- **Latin-centric**: only `latn`/`DFLT` with the default LangSys; no per-language systems, no complex scripts.

SafeStbTrueTypeSharp.sln

@@ -1,14 +1,10 @@
-
+
 Microsoft Visual Studio Solution File, Format Version 12.00
 # Visual Studio 15
 VisualStudioVersion = 15.0.28010.2036
 MinimumVisualStudioVersion = 10.0.40219.1
-Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Samples", "Samples", "{14A355A8-A827-4D09-B3A4-4C7A0EF983EC}"
-EndProject
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "StbSharp", "StbSharp", "{314ACA14-EC1F-4ECF-B902-A3D79850A1B2}"
 EndProject
-Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "StbTrueTypeSharp.MonoGame.Test", "samples\StbTrueTypeSharp.MonoGame.Test\StbTrueTypeSharp.MonoGame.Test.csproj", "{5528B473-7EEA-43EF-8DE2-6338C5F157D2}"
-EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "SafeStbTrueTypeSharp", "src\SafeStbTrueTypeSharp.csproj", "{B185B747-2A52-496F-83A3-94E3814963D9}"
 EndProject
 Global
@@ -17,10 +13,6 @@ Global
 		Release|Any CPU = Release|Any CPU
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 	GlobalSection(ProjectConfigurationPlatforms) = postSolution
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-		{5528B473-7EEA-43EF-8DE2-6338C5F157D2}.Debug|Any CPU.Build.0 = Debug|Any CPU
-		{5528B473-7EEA-43EF-8DE2-6338C5F157D2}.Release|Any CPU.ActiveCfg = Release|Any CPU
-		{5528B473-7EEA-43EF-8DE2-6338C5F157D2}.Release|Any CPU.Build.0 = Release|Any CPU
 		{B185B747-2A52-496F-83A3-94E3814963D9}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
 		{B185B747-2A52-496F-83A3-94E3814963D9}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{B185B747-2A52-496F-83A3-94E3814963D9}.Release|Any CPU.ActiveCfg = Release|Any CPU
@@ -29,9 +21,6 @@ Global
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE
 	EndGlobalSection
-	GlobalSection(NestedProjects) = preSolution
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 	GlobalSection(ExtensibilityGlobals) = postSolution
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