Render larger registered Japanese outlines

changelog.d/registered-japanese-outlines.md

@@ -0,0 +1 @@
+fix: **Registered Japanese outlines**: Larger registered-font glyphs such as `鬱` now render instead of falling back to blocks.

src/primitives/canvas/font_ttf.zig

@@ -9,10 +9,10 @@
 //! shaping, no CFF. The deterministic estimator (`text_metrics.zig`)
 //! derives its advance table from this face's `cmap`/`hmtx`, so layout
 //! measures with exactly the advances these outlines are inked at.
-//! All parsing is bounds-checked against fixed budgets sized from
-//! the bundled face's `maxp` (96 points / 16 contours per simple glyph,
-//! composites well under both), and any glyph beyond the budget fails
-//! with a recoverable error so callers can fall back to block glyphs.
+//! All parsing is bounds-checked against fixed budgets sized from the
+//! bundled and registered-face fixtures (237 points / 26 contours per
+//! simple glyph), and any glyph beyond the budget fails with a recoverable
+//! error so callers can fall back to block glyphs.
 //!
 //! The bundled face is embedded at comptime and its table directory is
 //! validated at comptime: a corrupt bundle is a compile error, and the
@@ -32,8 +32,11 @@ pub const Error = error{
     FontGlyphTooComplex,
 } || @import("vector.zig").Error;
 
-pub const max_glyph_points: usize = 128;
-pub const max_glyph_contours: usize = 24;
+pub const max_glyph_points: usize = 237;
+pub const max_glyph_contours: usize = 26;
+/// A simple glyph emits at most one segment per point plus one move and
+/// one close for each contour.
+pub const max_simple_glyph_path_elements: usize = max_glyph_points + 2 * max_glyph_contours;
 pub const max_composite_depth: usize = 4;
 pub const max_composite_components: usize = 8;
 

src/primitives/canvas/font_ttf_tests.zig

@@ -11,6 +11,7 @@ const drawing = @import("drawing.zig");
 
 const PointF = geometry.PointF;
 const Affine = drawing.Affine;
+const japanese_boundary_bytes = @embedFile("testdata/noto-japanese-boundary/NotoSansJP-japanese-boundary.ttf");
 
 const grid_size: usize = 24;
 
@@ -203,6 +204,29 @@ test "mono outlines rasterize within the vector budgets" {
     }
 }
 
+test "registered Japanese outlines render at the parser boundary" {
+    const face = try font_ttf.Face.parse(japanese_boundary_bytes);
+    const expected = [_]u21{ 'ば', 'ぱ', 'ぼ', 'ぽ', 'ゑ', '鬱' };
+    var max_emitted: usize = 0;
+    for (expected) |codepoint| {
+        const glyph = face.glyphIndex(codepoint);
+        try std.testing.expect(glyph != 0);
+        var builder = vector.PathBuilder(font_ttf.max_simple_glyph_path_elements){};
+        try face.glyphOutline(glyph, Affine.identity(), &builder);
+        try std.testing.expect(builder.slice().len > 0);
+        max_emitted = @max(max_emitted, builder.slice().len);
+    }
+    try std.testing.expectEqual(@as(usize, 243), max_emitted);
+    try std.testing.expectEqual(@as(usize, 289), font_ttf.max_simple_glyph_path_elements);
+
+    var mapped: usize = 0;
+    var codepoint: u21 = 0;
+    while (codepoint <= 0xFFFF) : (codepoint += 1) {
+        if (face.glyphIndex(codepoint) != 0) mapped += 1;
+    }
+    try std.testing.expectEqual(expected.len, mapped);
+}
+
 test "corrupt font bytes fail to parse without crashing" {
     try std.testing.expectError(error.FontParseFailed, font_ttf.Face.parse(&.{}));
     try std.testing.expectError(error.FontParseFailed, font_ttf.Face.parse(font_ttf.geist_regular_bytes[0..64]));

src/primitives/canvas/reference.zig

@@ -44,9 +44,8 @@ const render_fingerprints = @import("render_fingerprints.zig");
 const vector = @import("vector.zig");
 const font_ttf = @import("font_ttf.zig");
 
-/// Element budget for one glyph outline: the bundled face's densest
-/// glyphs stay well under this (maxp: 96 points per simple glyph).
-const reference_glyph_path_capacity: usize = 256;
+/// Element budget for every simple glyph accepted by the bounded parser.
+const reference_glyph_path_capacity: usize = font_ttf.max_simple_glyph_path_elements;
 
 const referenceBlurKernel = reference_blur.referenceBlurKernel;
 const referenceBlurSampleWithKernel = reference_blur.referenceBlurSampleWithKernel;
@@ -1074,7 +1073,6 @@ fn referenceScaleRect(rect: geometry.RectF, scale: f32) geometry.RectF {
     return geometry.RectF.init(rect.x * scale, rect.y * scale, rect.width * scale, rect.height * scale);
 }
 
-
 fn referencePixelCenter(x: usize, y: usize) geometry.PointF {
     return geometry.PointF.init(@as(f32, @floatFromInt(x)) + 0.5, @as(f32, @floatFromInt(y)) + 0.5);
 }

src/primitives/canvas/testdata/noto-japanese-boundary/OFL.txt

@@ -0,0 +1,93 @@
+Copyright 2014-2021 Adobe (http://www.adobe.com/), with Reserved Font Name 'Source'
+
+This Font Software is licensed under the SIL Open Font License, Version 1.1.
+This license is copied below, and is also available with a FAQ at:
+https://scripts.sil.org/OFL
+
+
+-----------------------------------------------------------
+SIL OPEN FONT LICENSE Version 1.1 - 26 February 2007
+-----------------------------------------------------------
+
+PREAMBLE
+The goals of the Open Font License (OFL) are to stimulate worldwide
+development of collaborative font projects, to support the font creation
+efforts of academic and linguistic communities, and to provide a free and
+open framework in which fonts may be shared and improved in partnership
+with others.
+
+The OFL allows the licensed fonts to be used, studied, modified and
+redistributed freely as long as they are not sold by themselves. The
+fonts, including any derivative works, can be bundled, embedded,
+redistributed and/or sold with any software provided that any reserved
+names are not used by derivative works. The fonts and derivatives,
+however, cannot be released under any other type of license. The
+requirement for fonts to remain under this license does not apply
+to any document created using the fonts or their derivatives.
+
+DEFINITIONS
+"Font Software" refers to the set of files released by the Copyright
+Holder(s) under this license and clearly marked as such. This may
+include source files, build scripts and documentation.
+
+"Reserved Font Name" refers to any names specified as such after the
+copyright statement(s).
+
+"Original Version" refers to the collection of Font Software components as
+distributed by the Copyright Holder(s).
+
+"Modified Version" refers to any derivative made by adding to, deleting,
+or substituting -- in part or in whole -- any of the components of the
+Original Version, by changing formats or by porting the Font Software to a
+new environment.
+
+"Author" refers to any designer, engineer, programmer, technical
+writer or other person who contributed to the Font Software.
+
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+Permission is hereby granted, free of charge, to any person obtaining
+a copy of the Font Software, to use, study, copy, merge, embed, modify,
+redistribute, and sell modified and unmodified copies of the Font Software,
+subject to the following conditions:
+
+1) Neither the Font Software nor any of its individual components,
+in Original or Modified Versions, may be sold by itself.
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+2) Original or Modified Versions of the Font Software may be bundled,
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+
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+
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+This license becomes null and void if any of the above conditions are
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+
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src/primitives/canvas/testdata/noto-japanese-boundary/README.md

@@ -0,0 +1,18 @@
+# Noto Sans JP Japanese outline boundary fixture
+
+`NotoSansJP-japanese-boundary.ttf` is a Modified Version of Noto Sans JP 2.004-H2 containing five kana glyphs and the common-use kanji `鬱`. The fixture exercises Native SDK's registered-font bounds up to 237 points and 26 contours. The complete SIL Open Font License is in `OFL.txt`.
+
+- Source commit: `google/fonts@295d98a7a0c17c68f1341eaeea354e7960ea70d3`
+- Source file SHA-256: `c2f3b4d463500a2ddcd3849cded1fceeb9fd6d1c32e6cbecd568453ba50fc68f`
+- Static Regular SHA-256: `946280470c7f8dff9c7256a10c6fb06544c75e83553e906a1a0ad946211de7ed`
+- Fixture SHA-256: `8a0c8b2e78eab29b4e26615a93695df8cc5eaae08ef981e517dc207069d9f308`
+- Generator: FontTools 4.63.0
+
+```sh
+workdir=$(mktemp -d)
+trap 'rm -rf "$workdir"' EXIT
+curl -fsSL 'https://raw.githubusercontent.com/google/fonts/295d98a7a0c17c68f1341eaeea354e7960ea70d3/ofl/notosansjp/NotoSansJP%5Bwght%5D.ttf' -o "$workdir/NotoSansJP-wght.ttf"
+export SOURCE_DATE_EPOCH=1784100876
+fonttools varLib.instancer "$workdir/NotoSansJP-wght.ttf" wght=400 --update-name-table --output="$workdir/NotoSansJP-Regular-400.ttf"
+pyftsubset "$workdir/NotoSansJP-Regular-400.ttf" '--unicodes=U+3070,U+3071,U+307C,U+307D,U+3091,U+9B31' --output-file=NotoSansJP-japanese-boundary.ttf '--name-IDs=*' --name-legacy '--name-languages=*'
+```