TTObjs unit

Contains objects definitions used in the FreeType (TrueType) library.

The four important objects managed by the library are:

Face: The object for a given typeface.
Instance: The object for a given pointsize/transform in a typeface.
Context: The object for a loading/hinting execution in a typeface.
Glyph: The object for a given glyph (outline and metrics).

A Face object is described by a TFace record, and its associated sub-tables. It is created through a call to the 'TT_Open_Face' API.

An Instance object is described by a TInstance record, and sub-tables. It is created for a given face through a call to the 'TT_Open_Instance' API. Several instances can share the same face.

The point size and/or transform of a given instance object can be changed on the fly through a call to the 'TT_Reset_Instance' API.

A Glyph object is used to describe a glyph to the client application It is made of a TGlyph_Record header, with several sub-tables used to store, for example, point coordinates or outline info. It can hold metrics information and other attributes, as well as the glyph's outline. A client application can request any kind of info to the library on a given glyph through the 'TT_Get_Glyph' call.

A Context is described by a TExec_Context record, and sub-tables Execution contexts are created on demand during the following operations:

Creating a new instance (to read and execute the font program).
Setting/resetting the point size (to execute the CVT program).
During glyph loading (when hinting is on).

They are used to run TrueType instructions and load/store glyph data that are not part of the Glyph object ( as they're of no meaning to a client application ).

The library keeps track of all objects related to a given face.

A face's instances are kept in two linked lists: one is the 'active' list, which tracks the face's current opened instances, while the other is the 'idle' list used to collect/recycle instance objects when they become unuseful after a 'TT_Close_Instance' call.

In the same way, a face's execution contexts are kept in two similar lists. Note that, as contexts are created on demand, the active and idle contexts lists should always contain few elements.

Look also for the following files:

Face manager: TTFace.pas
Instance manager: TTInst.pas
Context manager: TTExec.pas
Glyph manager: TTGlyph.pas

Classes and records

`TCallRecord`	record	Defines a call record used to manage function calls.
`TCodeRange`	record	Defines a code range.
`TDefRecord`	record	Defines a function / instruction definition record.
`TExec_Context`	record	FreeType Execution Context Object.
`TFace`	record	The FreeType Face object.
`TFont_Input`	record
`TGlyph`	record	FreeType Glyph Object.
`TGlyph_Transform`	record
`TGlyph_Zone`	record
`TGraphicsState`	record	Graphics State.
`TIns_Metrics`	record
`TInstance`	record	FreeType Instance Object.
`TSubglyph_Record`	record

Procedures and functions

`Clear_CodeRange`	function	Clear a given code range.
`Context_Load`	procedure
`Context_Run`	function
`Context_Save`	procedure
`Done_Context`	procedure
`Get_CodeRange`	function	Returns a pointer to a given code range record.
`Goto_CodeRange`	function	Go to a specified code range.
`Instance_Init`	function
`Instance_Reset`	function
`New_Context`	function
`Scale_X`	function
`Scale_Y`	function
`Set_CodeRange`	function	Sets properties for the given code range.
`TTObjs_Done`	procedure	Finalize the object manager.
`TTObjs_Init`	function	Initialize the object manager.

Types

`PCallStack`	type
`PCodeRange`	type
`PDefArray`	type
`PDefRecord`	type
`PExec_Context`	type
`PFace`	type
`PFont_Input`	type
`PGlyph`	type
`PGlyph_Transform`	type
`PGlyph_Zone`	type
`PGraphicsState`	type	Pointer to a TGraphicsState record type.
`PInstance`	type
`PSubglyph_Record`	type
`PSubglyph_Stack`	type
`TCallStack`	type	Defines a simple call stack.
`TCodeRangeTable`	type	Defines a code range.
`TDefArray`	type
`TFunc_Get_CVT`	procedure type	Reads a CVT value.
`TFunc_Set_CVT`	procedure type	Setting or Moving a CVT value.
`TMove_Function`	procedure type	Point displacement along the freedom vector routine, as used by the interpreter.
`TProject_Function`	procedure type	Distance projection along one of the proj. vectors, as used by the interpreter.
`TRound_Function`	procedure type	Rounding function, as used by the interpreter.
`TSubglyph_Stack`	type

Constants

`CvtFlag_Both`	constant
`CvtFlag_None`	constant
`CvtFlag_X`	constant
`CvtFlag_Y`	constant
`Default_GraphicsState`	constant
`MaxCodeRanges`	constant	Maximum number of code ranges.
`TT_CodeRange_Cvt`	constant
`TT_CodeRange_Font`	constant
`TT_CodeRange_Glyph`	constant

Variables

`exec_cache`	variable
`face_cache`	variable

Uses

An experiment, built from development snapshots. Not the official Free Pascal or Lazarus documentation.