{
    "mode": "perldoc",
    "parameter": "Font::TTF::Silf",
    "section": "",
    "url": "https://www.chedong.com/phpMan.php/perldoc/Font%3A%3ATTF%3A%3ASilf/json",
    "generated": "2026-06-14T05:38:29Z",
    "sections": {
        "NAME": {
            "content": "Font::TTF::Silf - The main Graphite table\n",
            "subsections": []
        },
        "DESCRIPTION": {
            "content": "The Silf table holds the core of the Graphite rules for a font. A Silf table has potentially\nmultiple silf subtables, although there is usually only one. Within a silf subtable, there are a\nnumber of passes which contain the actual finite state machines to match rules and the\nconstraint and action code to be executed when a rule matches.\n",
            "subsections": []
        },
        "INSTANCE VARIABLES": {
            "content": "Version\nSilf table format version\n\nCompiler\nLowest compiler version necessary to fully support the semantics expressed in this Graphite\ndescription\n\nSILF\nAn array of Silf subtables\n\nmaxGlyphID\nThe maximum glyph id referenced including pseudo and non glyphs\n\nAscent\nExtra ascent to be added to the font ascent.\n\nDescent\nExtra descent to be added to the font descent. Both values are assumed to be positive\nfor a descender below the base line.\n\nsubstPass\nPass index into PASS of the first substitution pass.\n\nposPass\nPass index into PASS of the first positioning pass.\n\njustPass\nPass index into PASS of the first justification pass.\n\nbidiPass\nPass index of the pass before which the bidirectional processing pass will be executed.\n0xFF indicates that there is no bidi pass to be executed.\n\nFlags\nA bitfield of flags:\n\n0 - Indicates there are line end contextual rules in one of the passes\n\nmaxPreContext\nMaximum length of a context preceding a cross line boundary contextualisation.\n\nmaxPostContext\nMaximum length of a context following a cross line boundary contextualsation.\n\nattrPseudo\nGlyph attribute for the actual glyph id associated with a pseudo glyph.\n\nattrBreakWeight\nGlyph attribute number of the attribute holding the default breakweight associated with\na glyph.\n\nattrDirectionality\nGlyph attribute number of the attribute holding the default directionality value\nassociated with a glyph.\n\nJUST\nThe may be a number of justification levels each with their own property values. This\npoints to an array of hashes, one for each justification level.\n\nattrStretch\nGlyph attribute number for the amount of stretch allowed before this glyph.\n\nattrShrink\nGlyph attribute number for the amount of shrink allowed before this glyph.\n\nattrStep\nGlyph attribute number specifying the minimum granularity of actual spacing\nassociated with this glyph at this level.\n\nattrWeight\nGlyph attribute number giving the weight associated with spreading space across a\nrun of glyphs.\n\nrunto\nWhich level starts the next stage.\n\nnumLigComp\nNumber of initial glyph attributes that represent ligature components\n\nnumUserAttr\nNumber of user defined slot attributes referenced. Tells the engine how much space to\nallocate to a slot for user attributes.\n\nmaxCompPerLig\nMaximum number of components per ligature.\n\ndirection\nSupported directions for this writing system\n\nCRITFEATURE\nArray of critical features.\n\nscripts\nArray of script tags that indicate which set of GDL rules to execute if there is more\nthan one in a font.\n\nlbGID\nGlyph ID of the linebreak pseudo glyph.\n\npseudos\nHash of Unicode values to pseduo glyph ids.\n\nclasses\nThis is an array of classes, each of which is an array of glyph ids in class order.\n\nPASS\nThe details of rules and actions are stored in passes. This value is an array of pass\nsubobjects one for each pass.\n\nflags\nThis is a bitfield:\n\n0 - If true, this pass makes no change to the slot stream considered as a sequence of glyph ids.\nOnly slot attributes are expected to change (for example during positioning).\n\nmaxRuleLoop\nHow many times the engine will allow rules to be tested and run without the engine\nadvancing through the input slot stream.\n\nmaxRuleContext\nNumber of slots of input needed to run this pass.\n\nmaxBackup\nNumber of slots by which the following pass needs to trail this pass (i.e. the\nmaximum this pass is allowed to back up).\n\nnumRules\nNumber of action code blocks, and so uncompressed rules, in this pass.\n\nnumRows\nNumber of rows in the finite state machine.\n\nnumTransitional\nNumber of rows in the finite state machine that are not final states. This specifies\nthe number of rows in the fsm element.\n\nnumSuccess\nNumber of success states. A success state may also be a transitional state.\n\nnumColumns\nNumber of columns in the finite state machine.\n\ncolmap\nA hash, indexed by glyphid, that gives the fsm column number associated with that\nglyphid. If not present, then the glyphid is not part of the fsm and will finish fsm\nprocessing if it occurs.\n\nrulemap\nAn array of arrays, one for each success state. Each array holds a list of rule\nnumbers associated with that state.\n\nminRulePreContext\nMinimum number of items in a rule's precontext.\n\nmaxRulePreContext\nThe maximum number of items in any rule's precontext.\n\nstartStates\nArray of starting state numbers dependeing on the length of actual precontext. There\nare maxRulePreContext - minRulePreContext + 1 of these.\n\nruleSortKeys\nAn array of sort keys one for each rule giving the length of the rule including its\nprecontext.\n\nrulePreContexts\nAn array of precontext lengths for each rule.\n\nfsm A two dimensional array such that $p->{'fsm'}[$row][$col] gives the row of the next\nnode to try in the fsm.\n\npassConstraintLen\nLength in bytes of the passConstraint code.\n\npassConstraintCode\nA byte string holding the pass constraint code.\n\nconstraintCode\nAn array of byte strings holding the constraint code for each rule.\n\nactionCode\nAn array of byte strings holding the action code for each rule.\n\n@opcodes\nEach array holds the name of the opcode, the number of operand bytes and a string describing the\noperands. The characters in the string have the following meaning:\n\nc - lsb of class id\nC - msb of class id\nf - feature index\ng - lsb of glyph attribute id\nG - msb of glyph attribute id\nl - lsb of a 32-bit extension to a 16-bit number\nL - msb of a 32-bit number\nm - glyph metric id\nn - lsb of a number\nN - msb of a 16-bit number\no - offset (jump)\ns - slot reference\nS - slot attribute id\nv - variable number of following arguments\n\nread\nReads the Silf table into the internal data structure\n\nout\nOutputs a Silf data structure to a font file in binary format\n\n$t->minsize()\nReturns the minimum size this table can be. If it is smaller than this, then the table must be\nbad and should be deleted or whatever.\n",
            "subsections": []
        },
        "AUTHOR": {
            "content": "Martin Hosken <http://scripts.sil.org/FontUtils>.\n",
            "subsections": []
        },
        "LICENSING": {
            "content": "Copyright (c) 1998-2016, SIL International (http://www.sil.org)\n\nThis module is released under the terms of the Artistic License 2.0. For details, see the full\ntext of the license in the file LICENSE.\n",
            "subsections": []
        }
    },
    "summary": "Font::TTF::Silf - The main Graphite table",
    "flags": [],
    "examples": [],
    "see_also": []
}