User axes from name IDs through the font. Each person begins with a credit score of 100 on which they construct their groups. To carry out these per-char lookups Harfbuzz might defer to FreeType (will describe later), or it might use its own OpenType implementation. Then it continues the lookups to categorise every char & run the statemachine, & for the first non-T-becoming a member of trailing char. Then it checks for leadings adopted by vowels with a potential (if font has the glyph) trailing merging them into a single cluster. The 3rd & non-compulsory (upon identical examine, for particular modes) combines diacretics into single char when thats what the font expects. These would get decoded to acceptable fetches & logic microcode, or for our common case: A single 32bit fetch! Or possibly they implement common https://soicaudb.com types of processing. Considers zero-width chars during processing Hangul tones. Which first checks for tones & whether or not to normalize by including dotted circles. After alphabet/script-specific logic it enables the Buzz & BUZZ options, adds, abvm/blwm/ccmp/locl/mark/mkmk/rlig features, adds calt/clig/curs/kern/liga/rclt features or if-vertical vert, iterates over caller-specified options adding every, possibly provides them once more to the AAT function, & provides the script a chance to override this config.
For Microsofts USE algorithm Harfbuzz registers a callback (to allocate syllable bits, lex into it, https://soicau333.com propagates a sure bitflag, aggregates bitflags, & iterates over syllables to propagate becoming a member of flags taking the aggregated flags under consideration), allows locl/ccmp/nukt/akhn features, deallocates substitution bitflags provides rphf function, registers a GSUB callback to iterate over syllables & their chars to see the place substitutions occurred, registers a substitution-deallocator GSUB callback once more, enables pref function, registers GSUB callback to record its use, allows rkrf/abvf/blwf/half/pstf/vatu/cjct options, registers a GSUB callback to insert dotted circles instead of lacking vowels & lightly reorders within every syllable, registers a syllabic bits deallocator GSUB callback, adds isol/initmedi/fina options, register null GSUB callback, & allows abvs/blws/haln/pres/psts options. The outer department https://burlingtoniwwforum.org chooses whether to apply this logic taking into account whether or not we need to be bug-compatible with Uniscribe. Malayalam has its personal base-c char logic bearing in mind joiners, halants, & consonants.
Again a lot of the logic is in adjusting the mapping. Unicode char-vary. Or it might must decompose, depending on the font. Afterwards font features are applied into these bits through a dynamic lookuptable over the appropriate ranges (unless that vary is your entire text) in the appropriate cluster. If it might shortcircuit it checks whether or not the pre-existing glyph already exists in the char, in that case repeatedly decomposes the char dealing with failures & along with all marks decomposes the cluster. For each variation selector codepoint in a cluster Harfbuzz iterates over said cluster searching for rare other variation selectors. The Indic writing system for autofitting purposes is treated as a minor variation upon CJK. When initializing the globals construction, FreeType iterates over all the charcodes for every writing system seeing which are present in the font (couple inside loops) whilst populating a lookuptable. An teration over writing systems to populate a metrics lookuptable. The basic writing methods FreeType understands for autofitting include latinate, indic, & CJK. Theres a routine abstracting glyph loading, adding unit conversion & a chance for the computed metrics, stem darkening, matrix transforms, the related writing system, and many others to include tweaks. Theres a routine which compiletime-may seek the advice of Harfbuzz retrieving all glyphs in the font & writing an unsigned quick to these indices in a given table.
This accelerator gathers & allocates abstract information upon initialization retrieving data from the fontface; wrapping a digest set, subtables array, & cache-person index quantity. Whilst outputting debug info. Creating a Harfbuzz shape plan entails validating a route & properties are given, allocating the structure, flags the fontface (fallingback to empty) as immutable, initialize the important thing, & init the OpenType data. Creating a cached Harfbuzz form plan entails checking whether or not its worth caching, if so allocating a caching key & iterate over a linkedlist looking for it, create the plan itself returning it instantly if were not caching, & allocating a node into that linkedlist. With that plan it repeatedly iterates over preserved tables computing what to maintain until fixpoint (each inner & outer loops), attaching a brand new accelerator throughout the fonts userdata after the actual fact. If the normalization-mode is auto itll choose an precise one based on whether the plan has a gpos mark.
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