Add registered font fallbacks and subsetting#30
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Introduce runtime-registered font support and per-annotation font subsetting for FreeText appearance generation. Adds CPDF_AnnotFontMap and CPDF_AnnotFontSubset to route fallback lookups to CFX_FontRegistry, create marker font entries in the AcroForm DR, and produce subsetted Type0/CIDFont dictionaries (using HarfBuzz) that embed only glyphs used by an annotation/layer. Update CPDF_Font::FallbackFontFromCharcode to prefer registered fonts and create runtime fallbacks, and switch FreeText AP generation to use CPDF_AnnotFontMap so resources include any registered fallback/subset fonts actually used. Expose UpdateDefaultAppearanceRegisteredFont to set a DA referencing a registered runtime font. Update BUILD.gn to include the new files and third_party/harfbuzz-ng, and add supporting CFX_FontRegistry and public/epdf_font glue.
Persist registered-font identity in marker font dictionaries and make font registry behavior robust. - Store registered font id in marker font dict (key "EmbedPDFRegisteredFontId") and add CPDF_AnnotFontSubset::GetRegisteredFontIdFromMarkerFontDict to read it. CPDF_AnnotFontMap now checks the marker dict for identity instead of inferring from BaseFont/resource alias. - Create marker font dicts with the new id field; make subset base-name comment deterministic. - Prevent CFX_FontRegistry::ClearRegisteredFonts from resetting next_font_id to avoid reusing ids that may still be referenced by existing document markers. - Update CPVT_FontMap unicode/charcode logic to use CharCodeFromUnicode checks and safe numeric conversions; preserve upstream appearance font selection behavior. - Add/adjust tests and helpers in fpdfsdk to validate stable appearance streams, alias-suffix survival, fallback rendering, checksums, and related utilities. - Update public API docs for font registration to clarify thread/ownership rules and ClearRegisteredFonts semantics. Also includes small cleanup/refactors and added includes needed by new code and tests.
Prefer registered-font mapping when generating appearance streams for persistent form widgets: if the target is persistent and there are registered fallback fonts or the font dict indicates a registered subset, create a CPDF_AnnotFontMap with registered fallbacks and embed the corresponding Font resources. Refactor duplicated AP generation into a lambda to reduce code duplication and preserve the previous CPVT_FontMap path for non-registered cases. Add CFX_FontRegistry::HasFallbackFonts() and its declaration. Add tests and a DroidSansFallbackFull.ttf test font, plus helpers to register and assert registered fallback behaviour for FreeText, TextField, ComboBox, and ListBox Korean glyphs. Also include small test fixes (initializer_list include, wchar_t usage).
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Introduce runtime-registered font support and per-annotation font subsetting for FreeText appearance generation. Adds CPDF_AnnotFontMap and CPDF_AnnotFontSubset to route fallback lookups to CFX_FontRegistry, create marker font entries in the AcroForm DR, and produce subsetted Type0/CIDFont dictionaries (using HarfBuzz) that embed only glyphs used by an annotation/layer. Update CPDF_Font::FallbackFontFromCharcode to prefer registered fonts and create runtime fallbacks, and switch FreeText AP generation to use CPDF_AnnotFontMap so resources include any registered fallback/subset fonts actually used. Expose UpdateDefaultAppearanceRegisteredFont to set a DA referencing a registered runtime font. Update BUILD.gn to include the new files and third_party/harfbuzz-ng, and add supporting CFX_FontRegistry and public/epdf_font glue.