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Author	SHA1	Message	Date
Benedikt Stebner	79ff4ff73e	[Text] Glyph Outline Part 5/13 - Shaped buffer glyph indices (#21501 ) * Fix glyph metrics; expose glyph bounding box GlyphMetrics previously stored the advance in Width/Height, leaving no field for the actual ink bounding box. Correct the contract: - Expand GlyphMetrics with AdvanceWidth / AdvanceHeight (and the bitmap / vertical-layout members XOffset / YOffset / VerticalOriginX/Y, reserved for later population). - Add GlyfTable.TryGetGlyphBounds: an allocation-free, header-only read of the glyph's control-point bounding box (xMin/yMin/xMax/yMax). Empty glyphs return true with zero bounds; out-of-range / short data return false. Composite glyphs use their header bbox without recursion. - TryGetGlyphMetrics (single + batch) now sources advances into AdvanceWidth / AdvanceHeight and the bounding box into Width / Height / XBearing / YBearing via TryGetGlyphBounds. Side bearings fall back to hmtx/vmtx when the glyph has no outline. The previously latent API had one test relying on the old behaviour (Width == advance); it's updated to assert AdvanceWidth. New tests cover TryGetGlyphBounds (range, empty, letter, descriptor parity) and the corrected metrics (advance placement, ink width distinct from advance, empty-glyph advance-without-ink, batch/single parity). * Add glyph-bounds benchmark GlyphBoundsBenchmark (Avalonia.Benchmarks): a BenchmarkDotNet comparison of the table-based bounds read against Skia's SKFont.GetGlyphWidths, in kernel (font pre-created) and per-run variants across 1 / 16 / 256 glyphs, with MemoryDiagnoser. * Add allocation-free batch glyph-bounds path Adds a bounds-only batch reader so ink-bounds computation (the GlyphRunImpl use case, which already has advances from shaping) doesn't pay for advance lookup or per-glyph indirection: - GlyphBounds: internal value type carrying the control-point box. - GlyfTable.GetGlyphBounds / GlyphTypeface.TryGetGlyphBounds: fetch the glyf and loca spans once per batch and read offsets + headers directly via BinaryPrimitives — no per-glyph ReadOnlyMemory.Span conversion, no intermediate Memory.Slice, no nested call chain. LocaTable exposes RawData / IsShortFormat for this. - Batch TryGetGlyphMetrics refactored onto the same span-cached reader. Measured against Skia's SKFont.GetGlyphWidths (bounds-only, in-process BenchmarkDotNet): the table path is faster at every run length (0.06× / 0.32× / 0.66× at 1 / 16 / 256 glyphs) and allocation-free, where Skia allocates 104 B/run for the SKFont. The earlier advance+bounds path via TryGetGlyphMetrics was ~2.2× slower than Skia at 256 glyphs; the bounds-only span-cached path is ~1.5× faster. The benchmark is updated to compare bounds-only on both sides. * Restore System.Buffers.Binary using in GlyfTable The glyf bounds readers (TryGetGlyphBounds / GetGlyphBounds) read the header int16s via BinaryPrimitives. The base pr2 commit trimmed this using as unused there, but it is needed once pr2b adds the bounds code — without it GlyfTable does not compile on this branch. * Clamp glyph bounding-box extents to non-negative GlyphBounds.Width/Height and both TryGetGlyphMetrics overloads computed the ink extent as (xMax - xMin) / (yMax - yMin). A malformed glyf header where xMax < xMin (or yMax < yMin) produced a negative value that, when narrowed to the ushort GlyphMetrics.Width/Height, wrapped to a huge positive extent instead of a safe zero. Clamp the extent to non-negative in GlyphBounds (the single source of truth for both the single and batch metric paths) and route the single TryGetGlyphMetrics path through GlyphBounds so both behave identically. For int16 coordinates the maximum extent is 65535 = ushort.MaxValue, so the clamped value always fits without overflow. Adds GlyphBoundsTests. * Allocate batch glyph-metric buffers only when their source is present Batch TryGetGlyphMetrics unconditionally sized the hMetrics, vMetrics and bounds temporary buffers to glyphIds.Length, even when the font has no hmtx, no vmtx, or no glyf table. For CFF/CFF2 fonts (no glyf) the bounds buffer is never read, and most fonts have no vmtx, so a large batch on such a font heap-allocated a per-glyph array that was pure waste. Size each buffer to zero — a free, empty stackalloc — when its source table is absent, so it only materialises (and only spills to the heap past 256 glyphs) when it will actually be filled and read. * Note the halved loca offsets in the batch bounds reader The short loca format stores every offset divided by two, which is why the batch reader doubles what it reads. LocaTable's single-glyph path already carries that note; the inline decode in the batch path did not. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> * Split the batch metrics loop on the glyf branch instead of per glyph The glyf check does not vary across the run, so it belongs above the loop rather than inside it. Splitting it also lets the bounds buffer live only in the branch that reads it, which drops the zero-length allocation that CFF / CFF2 fonts used to make just to satisfy the shared loop. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> * Add vertical glyph advance API to GlyphTypeface Mirror the existing TryGetHorizontalGlyphAdvance / ...Advances pair with vertical equivalents. Until now a vertical-layout caller (CJK, Mongolian) had no advance-only path on GlyphTypeface and had to go through TryGetGlyphMetrics, which after PR2b reads the glyf bounding box per glyph — pure waste when only the advance is needed. VerticalMetricsTable already exposes the per-glyph and batch readers internally (used by TryGetGlyphMetrics(batch)); this is a thin wrapper over them. Tests cover the Latin (no vmtx → false) and CJK (vmtx → positive advances) cases and batch/single parity using Inter and MiSans-Normal. Audit note: HorizontalMetricsTable and VerticalMetricsTable batch readers already span-cache (each fetches _data.Span once per call, reusing a BigEndianBinaryReader across glyphs). No metrics-table refactor is needed — the speculative Part 2 of the plan collapses to nothing. * Expose contiguous glyph indices span on ShapedBuffer Consumers that need a ReadOnlySpan<ushort> of glyph IDs (the upcoming GlyphTypeface.TryGetGlyphBounds batch path, SKFont.GetGlyphWidths, atlas lookups...) previously had to allocate a parallel ushort[] and project GlyphInfo.GlyphIndex into it. Carry that array on the ShapedBuffer instead: - ShapedBuffer rents a parallel ushort[] from ArrayPool alongside the existing GlyphInfo[] rental, exposed as `public ReadOnlySpan<ushort> GlyphIndices`. - The indexer setter syncs both, so HarfBuzz shaping and post-shape mutators (InterWordJustification rewrites the same GlyphIndex) keep the parallel view in lockstep with no caller change. - Split / WithBidiLevel slice the indices alongside the GlyphInfos at the same offsets — both share the parent's pooled arrays. - Dispose returns both rentals. Consumer wiring: - GlyphRunImpl: copies ShapedBuffer.GlyphIndices once via CopyTo when the source is a ShapedBuffer, dropping the per-glyph extract from the position loop. - TextFormatterImpl.CreateEmptyTextLine: switched to the pooled public ctor + indexer (was passing a heap-allocated GlyphInfo[] to the internal slice ctor, which now requires a parallel ushort slice). Tests cover indexer sync, overwrite, ascending split alignment, empty-leading split, and dispose clearing the view. --------- Co-authored-by: Claude Opus 5 <noreply@anthropic.com>	2 weeks ago

Author

SHA1

Message

Date

Benedikt Stebner

79ff4ff73e

[Text] Glyph Outline Part 5/13 - Shaped buffer glyph indices (#21501 )

* Fix glyph metrics; expose glyph bounding box

GlyphMetrics previously stored the advance in Width/Height, leaving no
field for the actual ink bounding box. Correct the contract:

- Expand GlyphMetrics with AdvanceWidth / AdvanceHeight (and the bitmap /
  vertical-layout members XOffset / YOffset / VerticalOriginX/Y, reserved
  for later population).
- Add GlyfTable.TryGetGlyphBounds: an allocation-free, header-only read of
  the glyph's control-point bounding box (xMin/yMin/xMax/yMax). Empty
  glyphs return true with zero bounds; out-of-range / short data return
  false. Composite glyphs use their header bbox without recursion.
- TryGetGlyphMetrics (single + batch) now sources advances into
  AdvanceWidth / AdvanceHeight and the bounding box into
  Width / Height / XBearing / YBearing via TryGetGlyphBounds. Side bearings
  fall back to hmtx/vmtx when the glyph has no outline.

The previously latent API had one test relying on the old behaviour
(Width == advance); it's updated to assert AdvanceWidth. New tests cover
TryGetGlyphBounds (range, empty, letter, descriptor parity) and the
corrected metrics (advance placement, ink width distinct from advance,
empty-glyph advance-without-ink, batch/single parity).

* Add glyph-bounds benchmark

GlyphBoundsBenchmark (Avalonia.Benchmarks): a BenchmarkDotNet comparison of
the table-based bounds read against Skia's SKFont.GetGlyphWidths, in kernel
(font pre-created) and per-run variants across 1 / 16 / 256 glyphs, with
MemoryDiagnoser.

* Add allocation-free batch glyph-bounds path

Adds a bounds-only batch reader so ink-bounds computation (the GlyphRunImpl
use case, which already has advances from shaping) doesn't pay for advance
lookup or per-glyph indirection:

- GlyphBounds: internal value type carrying the control-point box.
- GlyfTable.GetGlyphBounds / GlyphTypeface.TryGetGlyphBounds: fetch the glyf
  and loca spans once per batch and read offsets + headers directly via
  BinaryPrimitives — no per-glyph ReadOnlyMemory.Span conversion, no
  intermediate Memory.Slice, no nested call chain. LocaTable exposes RawData
  / IsShortFormat for this.
- Batch TryGetGlyphMetrics refactored onto the same span-cached reader.

Measured against Skia's SKFont.GetGlyphWidths (bounds-only, in-process
BenchmarkDotNet): the table path is faster at every run length (0.06× / 0.32×
/ 0.66× at 1 / 16 / 256 glyphs) and allocation-free, where Skia allocates
104 B/run for the SKFont. The earlier advance+bounds path via
TryGetGlyphMetrics was ~2.2× slower than Skia at 256 glyphs; the bounds-only
span-cached path is ~1.5× faster.

The benchmark is updated to compare bounds-only on both sides.

* Restore System.Buffers.Binary using in GlyfTable

The glyf bounds readers (TryGetGlyphBounds / GetGlyphBounds) read the
header int16s via BinaryPrimitives. The base pr2 commit trimmed this
using as unused there, but it is needed once pr2b adds the bounds code —
without it GlyfTable does not compile on this branch.

* Clamp glyph bounding-box extents to non-negative

GlyphBounds.Width/Height and both TryGetGlyphMetrics overloads computed
the ink extent as (xMax - xMin) / (yMax - yMin). A malformed glyf header
where xMax < xMin (or yMax < yMin) produced a negative value that, when
narrowed to the ushort GlyphMetrics.Width/Height, wrapped to a huge
positive extent instead of a safe zero.

Clamp the extent to non-negative in GlyphBounds (the single source of
truth for both the single and batch metric paths) and route the single
TryGetGlyphMetrics path through GlyphBounds so both behave identically.
For int16 coordinates the maximum extent is 65535 = ushort.MaxValue, so
the clamped value always fits without overflow. Adds GlyphBoundsTests.

* Allocate batch glyph-metric buffers only when their source is present

Batch TryGetGlyphMetrics unconditionally sized the hMetrics, vMetrics and
bounds temporary buffers to glyphIds.Length, even when the font has no
hmtx, no vmtx, or no glyf table. For CFF/CFF2 fonts (no glyf) the bounds
buffer is never read, and most fonts have no vmtx, so a large batch on
such a font heap-allocated a per-glyph array that was pure waste.

Size each buffer to zero — a free, empty stackalloc — when its source
table is absent, so it only materialises (and only spills to the heap
past 256 glyphs) when it will actually be filled and read.

* Note the halved loca offsets in the batch bounds reader

The short loca format stores every offset divided by two, which is why the
batch reader doubles what it reads. LocaTable's single-glyph path already
carries that note; the inline decode in the batch path did not.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

* Split the batch metrics loop on the glyf branch instead of per glyph

The glyf check does not vary across the run, so it belongs above the loop
rather than inside it. Splitting it also lets the bounds buffer live only
in the branch that reads it, which drops the zero-length allocation that
CFF / CFF2 fonts used to make just to satisfy the shared loop.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

* Add vertical glyph advance API to GlyphTypeface

Mirror the existing TryGetHorizontalGlyphAdvance / ...Advances pair with
vertical equivalents. Until now a vertical-layout caller (CJK, Mongolian)
had no advance-only path on GlyphTypeface and had to go through
TryGetGlyphMetrics, which after PR2b reads the glyf bounding box per
glyph — pure waste when only the advance is needed.

VerticalMetricsTable already exposes the per-glyph and batch readers
internally (used by TryGetGlyphMetrics(batch)); this is a thin wrapper
over them.

Tests cover the Latin (no vmtx → false) and CJK (vmtx → positive
advances) cases and batch/single parity using Inter and MiSans-Normal.

Audit note: HorizontalMetricsTable and VerticalMetricsTable batch readers
already span-cache (each fetches _data.Span once per call, reusing a
BigEndianBinaryReader across glyphs). No metrics-table refactor is
needed — the speculative Part 2 of the plan collapses to nothing.

* Expose contiguous glyph indices span on ShapedBuffer

Consumers that need a ReadOnlySpan<ushort> of glyph IDs (the upcoming
GlyphTypeface.TryGetGlyphBounds batch path, SKFont.GetGlyphWidths, atlas
lookups...) previously had to allocate a parallel ushort[] and project
GlyphInfo.GlyphIndex into it. Carry that array on the ShapedBuffer instead:

- ShapedBuffer rents a parallel ushort[] from ArrayPool alongside the
  existing GlyphInfo[] rental, exposed as
  `public ReadOnlySpan<ushort> GlyphIndices`.
- The indexer setter syncs both, so HarfBuzz shaping and post-shape
  mutators (InterWordJustification rewrites the same GlyphIndex) keep
  the parallel view in lockstep with no caller change.
- Split / WithBidiLevel slice the indices alongside the GlyphInfos at
  the same offsets — both share the parent's pooled arrays.
- Dispose returns both rentals.

Consumer wiring:
- GlyphRunImpl: copies ShapedBuffer.GlyphIndices once via CopyTo when
  the source is a ShapedBuffer, dropping the per-glyph extract from the
  position loop.
- TextFormatterImpl.CreateEmptyTextLine: switched to the pooled public
  ctor + indexer (was passing a heap-allocated GlyphInfo[] to the
  internal slice ctor, which now requires a parallel ushort slice).

Tests cover indexer sync, overwrite, ascending split alignment,
empty-leading split, and dispose clearing the view.

---------

Co-authored-by: Claude Opus 5 <noreply@anthropic.com>

2 weeks ago

1 Commits (main)