• Various fuzzing and build fixes.
• Various subsetting fixes.
• Fix AAT insertion at the end of the text.
• Fix various rendering bugs in the experimental GPU library.
• WASM shaper code can now read the user features.

• Changes affecting shaping output:

  • Lookup order is now respected for mark positioning in the cross-direction (y in horizontal text, x in vertical text): marks no longer follow a cross-direction shift that a later lookup applies to the base. This improves compatibility with DirectWrite and Core Text.
  • Fix mark attachment to ligatures formed from decomposed glyphs.
  • The calt feature in Hangul text is now disabled only for the Jamos, not the whole buffer.

• Support for partially instancing version of avar table, as well as CFF2 table.

• New fill-glyph paint operation and APIs for the common case of filling a glyph with a solid color.

• New API to fetch assorted raw values from the OS/2, head, and post tables.

• New experimental API to extract a font’s glyph dependency graph, that applications can use to compute glyph closures themselves without running the subsetter.

• New subset flag to convert the charset of a subsetted CID-keyed CFF fonts into identity charset, and a matching hb-subset option. Useful for embedding fonts in PDF.

• Command-line utilities now handle non-ASCII arguments correctly on Windows.

• Various instancing and subsetting fixes.

• Various fixes to the experimental harfbuzz-vector, harfbuzz-raster and harfbuzz-gpu libraries.

• Various improvements to the HarfRust integration shaper.

• Various build, CI, portability, and fuzzing fixes.

• New API:

  • OpenType:
    +HB_OT_BITS_TAG_FS_TYPE
    +HB_OT_BITS_TAG_FS_SELECTION
    +HB_OT_BITS_TAG_MAC_STYLE
    +HB_OT_BITS_TAG_IS_FIXED_PITCH
    +HB_OT_BITS_TAG_UNICODE_RANGE_1
    +HB_OT_BITS_TAG_UNICODE_RANGE_2
    +HB_OT_BITS_TAG_UNICODE_RANGE_3
    +HB_OT_BITS_TAG_UNICODE_RANGE_4
    +HB_OT_BITS_TAG_CODE_PAGE_RANGE_1
    +HB_OT_BITS_TAG_CODE_PAGE_RANGE_2
    +HB_OT_NUMBER_TAG_FONT_X_MIN
    +HB_OT_NUMBER_TAG_FONT_Y_MIN
    +HB_OT_NUMBER_TAG_FONT_X_MAX
    +HB_OT_NUMBER_TAG_FONT_Y_MAX
    +hb_ot_bits_tag_t
    +hb_ot_fetch_bits()
    +hb_ot_number_tag_t
    +hb_ot_fetch_number()

  • Paint:
    +hb_paint_fill_glyph_func_t
    +hb_paint_fill_glyph()
    +hb_paint_funcs_set_fill_glyph_func()

  • Subset library:
    +HB_SUBSET_FLAGS_CFF_IDENTITY_CHARSET

• Various AAT shaping fixes: legacy mort contextual offsets (which could produce out-of-font glyph IDs), in-place deleted-glyph replacements, and overflow in obsolete offset math.
• Fix Arabic PUA fallback shaping for the isolated lam-alef-maksura ligature.
• Fix float-to-int overflow in avar2 mapping with malformed fonts.
• Harden buffer verification after detecting non-monotone clusters.
• Various COLR v1 fixes: fix handling of .notdef without paint, round alpha consistently, and report the root clip under the font transform.
• Various Glyph-extents fixes: inclusive rounding, and floating-point scaling before rounding so the reported box always covers the glyph.
• Various Subsetting fixes: keep the palt spacing feature by default, raise the repacker MAX_SPACES limit, fix a repacker crash on shared LigatureSet nodes, guard gvar size overflow on 32-bit, and fix the post glyph-name sort comparator on macOS.
• Replace std::sort with an internal quicksort, removing leaked std:: symbols from the libharfbuzz ABI.
• Harden size computations with saturating arithmetic against 32-bit overflow.
• Various improvements to the experimental Rust shaper (HarfRust) and font functions (fontations): honor custom font funcs, key shape plans on features, faster buffer handling, and update to HarfRust 0.8.
• Various fixes to the experimental harfbuzz-gpu and harfbuzz-vector libraries, including a harfbuzz-vector heap buffer overflow and Windows build fixes.
• Map the Hrkt (Katakana or Hiragana) script tag to the kana OpenType tag.
• Build configuration: new HB_CONFIG_OVERRIDE_LAST_H override header, decouple HB_NO_DRAW from HB_NO_CFF, and an optional hb-allocator Cargo feature.
• Various build, CI, and fuzzing fixes.

In this release, the experimental raster, vector, and GPU libraries went through several rounds of code review and cleanup to make sure they follow the high standards expected of HarfBuzz code. The API has also been extensively reviewed based on experience gained from using these libraries. We consider the code and API to be ready for stabilization, and we expect to graduate them from experimental in the near future. If you are using or planning to use these libraries and have any concerns about the API, it is time to raise them. Once a library is deemed stable, we will never change the API or ABI in an incompatible way.

• GPU library:

  • New color-glyph paint renderer, based on design by Lê Duy Quang.
    hb_gpu_paint_t walks a font's paint tree (COLRv0 or COLRv1) and encodes its layers (solid fills, linear / radial / sweep gradients, transforms, composite groups) into a compact blob.
    A new fragment-shader function hb_gpu_paint() renders the blob in premultiplied RGBA; monochrome glyphs are handled transparently via a synthesized foreground-colored layer.
    Shader sources provided in GLSL, WGSL, MSL, and HLSL.
  • Paint encoder limitations: the encoder sets unsupported and returns NULL when num_ops would exceed 32767, push_group nests deeper than 4, or the paint tree calls back through the image callback (PaintImage).
    Nested glyph clips are intersected up to 3 levels; a few composite modes use approximate fallbacks; push_clip_rectangle is silently ignored.
  • Encode entry point now returns extents and auto-clears the encoder; the standalone get_extents() is gone.
  • Gradient color stop interpolation now happens in premultiplied space per the OpenType COLR specification.
  • The foreground color sentinel (is_foreground) now correctly preserves the paint-tree alpha from the encoded color data instead of discarding it.
  • The hb-gpu utility gains --draw / --paint flags with per-font auto-detect, and --output-file / -o for headless single-frame rendering to a PPM image.

• Vector library:

  • New PDF output backend. Vector paint glyphs now render to PDF page content, producing scalable COLRv0 / COLRv1 color-glyph artwork (solid fills, linear / radial / sweep gradients, blend modes, PNG images with transparency) that can be embedded directly in PDF documents. Useful for PDF producers such as LibreOffice that want crisp, resolution-independent color emoji.
  • New SVG id prefix API on paint allows prefixing document references, which allows for embedding multiple SVGs in the same page without name clashes (hb_vector_paint_set_svg_prefix).
  • Removed glyph path dedup from vector draw and paint. Each glyph is emitted inline; no <defs> / <use> caching.
  • _glyph() functions are now thin convenience wrappers documented as equivalent expansions of the underlying font draw/paint API.
  • Drop glyph-source rendering of SVG-in-OT fonts.

• Raster library:

  • Drop glyph-source rendering of SVG-in-OT fonts.

• Across Draw / Paint subsystems:

  • _reset() methods gain matching_clear() companions that drop accumulated data while preserving user configuration. Getter companions added for setters across raster, vector, and gpu types.

• Various fuzzer fixes for raster, vector, and GPU libraries.

• Paint API:

  • New arbitrary-path clip: hb_paint_push_clip_path_start / _end let callers clip to a caller-supplied outline, not just a font glyph. push_clip_path_start() returns the draw-funcs (and matching draw data) for the backend’s path accumulator; the caller drives hb_draw_*() into it, then calls push_clip_path_end(), followed by painted ops, then hb_paint_pop_clip() to release the clip. Implemented for all paint backends: vector (SVG defs + clipPath + url ref), vector PDF (q / path / W n), raster (path rendered to an alpha mask, intersected with the current clip), and GPU (the path is encoded into a Slug sub-blob so the fragment shader clips against it the same way it clips against glyph outlines).

• Shaping:

  • Indic: categorize U+1CF5 and U+1CF6 as CS.

• Changed API

  • GPU library:

    • hb_gpu_draw_glyph() now returns void (was hb_bool_t). Use hb_gpu_draw_glyph_or_fail() if you need the success status.
    • hb_gpu_paint_glyph() now returns void (was hb_bool_t) and internally synthesizes a foreground-colored layer for non-color glyphs via hb_font_paint_glyph(), so every glyph with an outline produces output. Use hb_gpu_paint_glyph_or_fail() (which delegates to hb_font_paint_glyph_or_fail()) if you need to distinguish color vs synthesized paint. Encoder-level limits (unsupported ops, group-stack overflow) no longer fail paint_glyph; they surface from hb_gpu_paint_encode() returning NULL.
    • hb_gpu_draw_encode() now takes an extents out-parameter and auto-clears the encoder on return.
    • hb_gpu_draw_darken() renamed to hb_gpu_stem_darken().

  • Vector library:

    • hb_vector_svg_set_precision() and its paint counterpart renamed to hb_vector_draw_set_precision() / hb_vector_paint_set_precision() (SVG-specific naming is inaccurate with the PDF backend added).
    • hb_vector_draw_glyph() / hb_vector_paint_glyph() now return void (were hb_bool_t). Paint additionally gains a draw fallback for non-color glyphs. Use the matching _or_fail() variants for the hb_bool_t return.

  • Raster library:

    • hb_raster_draw_glyph() / hb_raster_paint_glyph() now return void (were hb_bool_t). Paint additionally gains a draw fallback for non-color glyphs. Use the matching _or_fail() variants for the hb_bool_t return.

  • General:

    • Many read-only getters gained const on their object argument.
    • Six public draw / paint funcs getters across raster, vector, and gpu now take a const-pointer to the relevant context instance instead of being singletons:
      hb_raster_draw_get_funcs (const hb_raster_draw_t *)`
      hb_raster_paint_get_funcs (const hb_raster_paint_t *)
      hb_vector_draw_get_funcs (const hb_vector_draw_t *)
      hb_vector_paint_get_funcs (const hb_vector_paint_t *)
      hb_gpu_draw_get_funcs (const hb_gpu_draw_t *)
      hb_gpu_paint_get_funcs (const hb_gpu_paint_t *)
      This is what lets vector_paint dispatch to SVG- vs PDF- flavored callbacks transparently when called from outside code; the others currently use the instance for symmetry only.

• New API

  • Draw:
    +HB_DRAW_LINE_CAP_BUTT
    +HB_DRAW_LINE_CAP_ROUND
    +HB_DRAW_LINE_CAP_SQUARE
    +hb_draw_line_cap_t
    +hb_draw_line()
    +hb_draw_rectangle()
    +hb_draw_circle()

  • Paint:
    +hb_paint_push_clip_path_start_func_t
    +hb_paint_push_clip_path_end_func_t
    +hb_paint_sweep_gradient_tile_func_t
    +hb_paint_push_group_for_func_t
    +hb_paint_push_group_for()
    +hb_paint_funcs_set_push_group_for_func()
    +hb_paint_reduce_linear_anchors()
    +hb_paint_normalize_color_line()
    +hb_paint_sweep_gradient_tiles()
    +hb_paint_push_clip_path_start()
    +hb_paint_push_clip_path_end()
    +hb_paint_funcs_set_push_clip_path_start_func()
    +hb_paint_funcs_set_push_clip_path_end_func()

  • GPU library:
    +HB_GPU_SHADER_STAGE_VERTEX
    +HB_GPU_SHADER_STAGE_FRAGMENT
    +HB_GPU_SHADER_LANG_INVALID
    +hb_gpu_shader_stage_t
    +hb_gpu_paint_t
    +hb_gpu_paint_create_or_fail()
    +hb_gpu_paint_reference()
    +hb_gpu_paint_destroy()
    +hb_gpu_paint_set_user_data()
    +hb_gpu_paint_get_user_data()
    +hb_gpu_paint_get_funcs()
    +hb_gpu_paint_set_palette()
    +hb_gpu_paint_get_palette()
    +hb_gpu_paint_set_custom_palette_color()
    +hb_gpu_paint_clear_custom_palette_colors()
    +hb_gpu_paint_set_scale()
    +hb_gpu_paint_get_scale()
    +hb_gpu_paint_glyph()
    +hb_gpu_paint_encode()
    +hb_gpu_paint_clear()
    +hb_gpu_paint_reset()
    +hb_gpu_paint_recycle_blob()
    +hb_gpu_paint_shader_source()
    +hb_gpu_paint_glyph_or_fail()
    +hb_gpu_shader_source()
    +hb_gpu_draw_shader_source()
    +hb_gpu_draw_clear()
    +hb_gpu_draw_get_scale()
    +hb_gpu_draw_glyph_or_fail()

  • Raster library:
    +hb_raster_draw_clear()
    +hb_raster_draw_glyph_or_fail()
    +hb_raster_paint_clear()
    +hb_raster_paint_glyph_or_fail()
    +hb_raster_paint_set_palette()
    +hb_raster_paint_get_palette()
    +hb_raster_paint_get_foreground()
    +hb_raster_paint_set_background()
    +hb_raster_paint_get_background()

  • Vector library:
    +HB_VECTOR_FORMAT_PDF
    +hb_vector_draw_clear()
    +hb_vector_draw_get_precision()
    +hb_vector_draw_get_format()
    +hb_vector_draw_glyph_or_fail()
    +hb_vector_draw_new_path()
    +hb_vector_draw_set_foreground()
    +hb_vector_draw_get_foreground()
    +hb_vector_draw_set_background()
    +hb_vector_draw_get_background()
    +hb_vector_paint_clear()
    +hb_vector_paint_get_precision()
    +hb_vector_paint_get_format()
    +hb_vector_paint_get_foreground()
    +hb_vector_paint_set_background()
    +hb_vector_paint_get_background()
    +hb_vector_paint_get_palette()
    +hb_vector_paint_glyph_or_fail()
    +hb_vector_paint_set_svg_prefix()
    +hb_vector_paint_get_svg_prefix()

• Removed API

  • GPU library:
    -hb_gpu_shader_fragment_source() (replaced by hb_gpu_shader_source(stage))
    -hb_gpu_shader_vertex_source() (replaced by hb_gpu_shader_source(stage))
    -hb_gpu_draw_get_extents() (extents are now an out-parameter of hb_gpu_draw_encode())

  • Vector library:
    -hb_vector_draw_set_flat()
    -hb_vector_draw_get_flat()
    -hb_vector_paint_set_flat()
    -hb_vector_paint_get_flat()

• GPU library improvements:
  • Add anti-aliased rendering for small sizes.
  • Store font scale in blob header.
  • Port scale/ppem support to MSL, WGSL, and HLSL shaders.
  • Fix contour breaks and bounds quantization in encode.
  • Fix garbled rendering after font change in web demo.
  • Various robustness fixes.
• Various fuzzing fixes for harfbuzz-raster, harfbuzz-gpu and harfbuzz-vector libraries.
• Move HB_NO_CFF from HB_LEAN to HB_NO_DRAW closure, and fix HB_TINY build.
• New API:
  +hb_gpu_draw_set_scale()

• New libharfbuzz-gpu library: GPU text rasterization based on the Slug algorithm by Eric Lengyel. Encodes glyph outlines on the CPU into compact blobs that the GPU decodes and rasterizes directly in the fragment shader, with no intermediate bitmap atlas.
  Shader sources provided in GLSL, WGSL, MSL, and HLSL.
  New hb-gpu installed utility for interactive GPU text rendering.
  Live web demo: https://harfbuzz.github.io/hb-gpu-demo/
• New harfbuzz-world.cc amalgamated source for building a subset of all HarfBuzz libraries into one compilation unit, driven by a custom hb-features.h.
• Updated README with libraries overview and project description.
• Various bug fixes.
• New API:
  • hb_gpu_draw_t
  • hb_gpu_draw_create_or_fail()
  • hb_gpu_draw_reference()
  • hb_gpu_draw_destroy()
  • hb_gpu_draw_set_user_data()
  • hb_gpu_draw_get_user_data()
  • hb_gpu_draw_get_funcs()
  • hb_gpu_draw_glyph()
  • hb_gpu_draw_encode()
  • hb_gpu_draw_get_extents()
  • hb_gpu_draw_reset()
  • hb_gpu_draw_recycle_blob()
  • hb_gpu_shader_lang_t
  • hb_gpu_shader_fragment_source()
  • hb_gpu_shader_vertex_source()

• Fix regression in tracing messages from previous release.

• Fix hb-view glyph positioning with --glyphs input from hb-shape --ned.
• Various fuzzing fixes for harfbuzz-subset, harfbuzz-raster and harfbuzz-vector libraries.
• Various improvements to tracing messages.
• Various documentation improvements.
• New API:
  • HB_OT_SHAPE_BUFFER_FORMAT_SERIAL
  • hb_ot_shape_get_buffer_format_serial()

• Support gzip-compressed SVG glyphs in harfbuzz-raster andharfbuzz-vector libraries. This new functionality requires zlib, and will not be available if HarfBuzz is built without zlib.
• Improve handling of SVG glyphs in harfbuzz-raster and harfbuzz-vector libraries.
• Further harden application of stch feature against malicious fonts.
• Various fuzzing fixes.
• Various build fixes:
  • Add missing chafa dependency to hb-raster utility, and remove accidental cairo dependency.
  • Don’t build raster and vector fuzzers if the library is disabled.
  • Add meson options for enabling / disabling libpng and zlib.
  • Support building harfbuzz-raster and harfbuzz-vector libraries with CMake.

• The harfbuzz-raster library can now render bitmap color glyph formats (CBDT and sbix). It now also has an API to serialize / deserialize images to and from PNGs. This new functionality requires libpng, and will not be available if HarfBuzz is built without libpng.
• Install hb-raster command line utility.
• Fix overflow when applying stch feature with malicious fonts.
• Fix memory leaks in harfbuzz-raster and harfbuzz-vector in error conditions, as well as more robust handling of allocation failures.
• Various documentation improvements and build fixes.
• New API:
  +hb_raster_image_serialize_to_png_or_fail()
  +hb_raster_image_deserialize_from_png_or_fail()