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The FreeType Engine Core Library Reference ----------------------------------- Table of Contents: Introduction I. Types II. Functions III. Error codes -------------------- Introduction: This reference presents the types, functions and error codes defined in the high-level API header file "freetype.h". Note that all symbols defined in this file are prefixed by "TT_", to avoid name conflicts with other packages at link time. Some of its parts are also dedicated to the extension that comes by default with this distribution of the library, which is kerning support. ---------------------------------------------------------------------------- I. Types: Here is the list of all the types defined in the core FreeType API. Their exact definition can be found in the file "freetype.h" which should be included by every client application. TT_Fixed A signed 16.16 fixed float value used to specify transform coefficients and other important data. .................................................................. TT_FWord A signed 16 bits value used to express a distance measured in the font's original EM units. These are also called 'FUnits' in the TrueType specification. .................................................................. TT_UFWord Unsigned FWord. .................................................................. TT_Short TT_UShort TT_Long TT_ULong These four types are aliases for 16 bits integer (signed and unsigned) and 32 bits one (signed and unsigned). .................................................................. TT_F2Dot14 A 2.14 fixed float integer used for unary vectors and some scaling coefficients. Their layout is: s : 1 -- sign bit m : 1 -- mantissa bit f : 14 -- unsigned fractional value where 's:m' is the 2-bit signed integer value to which the always-positive fractional part 'f' should be added. .................................................................. TT_F26Dot6 The 26.6 fixed float format used to define fractional pixel coordinates. Here, 1 unit = 1/64 pixel. .................................................................. TT_UnitVector A simple structure used to store a unit vector. The vector's coordinates are expressed in fixed float format (2.14). struct { TT_F2Dot14 x; TT_F2Dot14 y; } .................................................................. TT_Vector A simple structure used to store a single vector. Its coordinates are expressed in fixed float format (26.6). struct { TT_F26Dot6 x; TT_F26Dot6 y; } .................................................................. TT_Matrix A simple structure used to store a single 2x2 matrix. Its coefficients are expressed in 16.16 fixed float format. This matrix is used to perform linear transformations on the glyph outline, such as slanting or rotation. struct { TT_Fixed xx, xy; TT_Fixed yx, yy; }; The computation performed is: x' = xx * x + xy * y y' = yx * x + yy * y .................................................................. TT_Glyph_Outline This structure is used to describe a vectorial glyph representation to the rasterizer. It is made of: - an array of points: The 'points' field gives the number of points in the outline, while their coordinates are found in the parallel arrays 'xCoord' and 'yCoord'. The 'flag' array holds for each point a flag indicating its type. Currently, only the first bit (bit 0, the least significant bit) of each byte is meaningful to the rasterizer. When set, it indicates that the point is _on_ the curve. When not set, the point is said to be _off_ the curve. It's then a Bezier control point. For more information about point states, read the TrueType specification or the scan-line documentation "raster.txt". - an array of contours' start-point indexes: The 'contours' field gives the number of contours, while the 'conStarts' array holds the indexes of each contour's first point. Note that the first contour always starts at 0 and has no entry in this table. Hence, conStarts[0] holds the index of the point starting the _second_ contour. The first one being defined by the closure of the path 0..conStarts[0]-1. ** IMPORTANT NOTE: ** ********************* The last table entry _must_ always give the total number of points used to draw the contours, i.e.: conStarts[contours-1] == points If this value is bigger than 'points' when calling the scan-line converter, the component will immediately return an error. If the value is smaller, only the points contained in the described contours will be used in the conversion process. - a dropout mode: Used to specify the method to apply for drop-out control (also called 'continuity testing' in other environments). The mode value must be one of the values defined by the TrueType specification. The recent modes 4 and 5 introduced in the newest spec (1.6) are fully supported. An invalid value (i.e., other than 0, 1, 2, 4, or 5) is taken as no dropout control (equivalent to mode 0). NOTE1: A typical user would only modify the point coordinates accessed through the 'xCoord' and 'yCoord' fields. Changing the number of points, the contours arrays or even the flags array is a delicate process that should be taken seriously. NOTE2: A glyph outline only contains pointers to the tables it describes, but it doesn't own them! Typically, the tables are defined and owned by a glyph container object (see below). They are accessed through a call to TT_Get_Glyph_Outline() which returns a TT_Glyph_Outline structure whose pointers relate to the container's data. These outline's tables should never be freed directly by the client application; they will be destroyed with the glyph container when the latter is discarded. struct { unsigned int contours; /* number of contours in glyph */ unsigned short* conStarts; /* points to an array of each contour's start point index */ unsigned int points; /* number of points in the glyph */ long* xCoord; /* table of x coordinates */ long* yCoord; /* table of y coordinates */ unsigned char* flag; /* table of flags */ char dropout_mode; /* dropout mode */ } .................................................................. TT_Glyph_Metrics A structure used to return simple glyph metrics. These values are expressed in fractional pixels (26.6 format) if scaling was active, and in FUnits otherwise. struct { TT_F26Dot6 leftSideBearing; TT_F26Dot6 advanceWidth; TT_F26Dot6 xMin, yMin, xMax, yMax; }; .................................................................. TT_Instance_Metrics A structure used to return instance (point size) metrics. struct { int pointSize; /* point size in points (1 point = 1/72 inch) */ int x_ppem; /* horizontal pixels per EM square */ int y_ppem; /* vertical pixels per EM square */ int x_resolution; /* device horizontal resolution in dpi */ int y_resolution; /* device vertical resolution in dpi */ }; .................................................................. TT_Raster_Map This structure is used to describe a target bitmap (or pixmap) to the scan-line converter. It must be set up by the client application. - the 'rows' field contains the total number of rows in the bitmap - the 'width' field gives the number of pixels per row (a bit or a byte, depending on the map's nature). - the 'cols' field gives the number of columns, i.e. bytes, taken by each row in the map buffer. ** IMPORTANT **: the 'cols' field must be a multiple of 4! Typically, its value should be '(width+7)/8' for bitmaps, and '(width+3) & -4' for pixmaps. - the 'flow' field gives the map's vertical orientation. For example, if the first bytes of the bitmap buffer pertain to its upper row, the flow is said to be going 'down', and the field should take the value 'TT_Flow_Down'. If these bytes pertain to its lowest row, the flow is going 'up', and the value is 'TT_Flow_Up'. As an example, the PC video modes use a 'down' flow, where the first VRAM byte corresponds to the upper and leftmost corner of the screen. - the 'bitmap' field is a typeless pointer to the map's buffer. - the 'size' field contains the buffer's size in bytes. It is usually computed as follows: size = rows * cols; NOTE: For bitmaps, the leftmost-pixel is related to the highest (i.e. most significant) bit of its byte. There is currently no support for the opposite convention found in some systems. (It can be easily added if you really need it, just ask the development team) struct { int rows; /* number of rows */ int cols; /* number of columns (bytes) per row */ int width; /* number of pixels per line */ int flow; /* bitmap orientation */ void* bitmap; /* bit/pixmap buffer */ long size; /* bit/pixmap size in bytes */ } TT_Raster_Map; .................................................................. TT_Header This structure is used to hold the font's header. Its layout and meaning are defined in the TrueType specification, in the 'head' section. .................................................................. TT_Horizontal_Header This structure is used to hold the font's horizontal header. Its layout and meaning are defined in the TrueType specification, in the 'hhead' section. .................................................................. TT_OS2 This structure is used to hold the font's OS/2 table. Its layout and meaning are defined in the TrueType specification, in the 'OS/2' section. .................................................................. TT_Postscript This structure is used to hold the font's Postscript table. Its layout and meaning are defined in the TrueType specification, in the 'post' section. .................................................................. TT_Face_Properties This structure is used to return an opened face's properties. These are: - The total number of glyphs in the font, given by the field 'num_Glyphs'. - The maximum number of points for the font's glyphs. This value is used to allocate the points tables of a glyph container's outline. It can be fairly large (like 256 points for Roman fonts). - The maximum number of contours for the font's glyphs. This value is used to allocate the contours tables of a glyph container's outline. It can be fairly large (over 16, even in Roman fonts). - The maximum number of associated faces. This number is always 0 for a normal TrueType font file. However, when the face object was opened from a TrueType collection, it contains the maximum embedded font index used within this font collection. - pointers to the face's header, horizontal header, OS/2, and Postscript tables. struct { int num_Glyphs; /* number of glyphs in face */ int max_Points; /* maximum number of points in a glyph */ int max_Contours; /* maximum number of contours in a glyph */ int max_Faces; /* 0 for normal TrueType files, and the */ /* number of embedded faces minus 1 for */ /* TrueType collections */ TT_Header* header; /* TrueType header table */ TT_Horizontal_Header* horizontal; /* TrueType horizontal header */ TT_OS2* os2; /* TrueType OS/2 table */ TT_Postscript* postscript; /* TrueType Postscript table */ } TT_Face_Properties; .................................................................. TT_Stream This handle type defines a stream used to access a font file's data. A client application should never deal with streams directly, but some engine extensions may later need it to support more advanced features like font embedding. .................................................................. TT_Face This type defines a handle used to reference a face object. The objects are never accessed directly by a client application; it can only obtain handles to new objects, and use them to query specific information or processes. See also: TT_Open_Face(), TT_Open_Collection(), TT_Close_Face(), TT_Get_Face_Properties(), etc. .................................................................. TT_Instance This type defines a handle used to reference an instance object (also called a 'pointsize' in other type engines). An instance is always created from a valid face object, and is destroyed with it by the engine. See also: TT_New_Instance(), TT_Close_Instance(), TT_Set_Instance_Pointsize(), TT_Set_Instance_Resolution(), etc. .................................................................. TT_Glyph This type defines a handle used to reference a glyph container object. A glyph container is an object owning tables sized to the font's maximum profile to hold any glyph of a given font file. It contains an outline, some metrics, as well as some data related to the way it should be processed by the scan-line converter. Note that a glyph container doesn't contain any bitmap nor pixmap! See also: TT_New_Glyph(), TT_Close_Glyph(), TT_Get_Glyph_Metrics(), TT_Get_Glyph_Outline(), TT_Get_Glyph_Bitmap(), TT_Get_Glyph_Pixmap() .................................................................. TT_Error This is the type of all error codes returned by the API. Nearly all functions return an error code, set to 0 in case of success. A list of all error codes is given in section III. .................................................................. This distribution comes with an extension used to support access to a font's kerning information. The extension's types and API are defined in the file "ftxkern.h" ---------------------------------------------------------------------------- II. Functions: Here is a list of the core library's API. NOTE: A function's default result is an error code of type TT_Error; a list of error codes is given in section III below. Some functions return integers or other types, in which case the result type is written with its description. .................................................................. TT_Init_FreeType(); Initialize the engine. This call must be performed before any other function of FreeType is invoked. .................................................................. TT_Done_FreeType(); Finalize the engine. This calls destroys _all_ objects that were previously created and used with the engine .................................................................. TT_Open_Face( char* fontpathname, TT_face* face ); This call opens a font file, located by 'fontpathname', and returns a handle to the newly corresponding face object in the handle '*face'. Example: error = TT_Open_Face( "c:\ttf\wingding.ttf", &face ); if ( error ) fprintf( stderr, "could not open face\n" ); Note: The font file can be a TrueType collection; in this case, the engine will always open the first embedded font found in the file. .................................................................. TT_Open_Collection( char* collectionpathname, int fontIndex, TT_Face* face ); This call opens one of the font files found in a TrueType collection. The file is selected through the 'fontIndex' argument. Note that to know a collection's number of embedded fonts, you'll have to: 1 - open the first collection font with TT_Open_Face(). 2 - query the face's properties through TT_Get_Face_Properties(). The number of embedded faces is then 'properties->max_Faces + 1'. Example: TT_Face face; TT_Face_Properties properties; error = TT_Open_Face( "c:\ttf\sample.ttc", &face ); if ( error ) { ...error .. } /* Open first embedded collection font */ error = TT_Get_Face_Properties( face, &properties ); if ( error ) { ...error .. } /* Get face metrics */ printf( "There are %d fonts in this collection", properties->max_Faces + 1 ); TT_Close_Face( face ); error = TT_Open_Collection( "c:\ttf\sample.ttc", 1, &face ); if ( error ) { ...error .. } /* Open second font in collection */ Note: If the file isn't a collection, 'fontIndex' must be zero. Otherwise, an error will be produced. .................................................................. TT_Get_Face_Properties( TT_Face face, TT_Face_Properties* properties ); Return the 'face' object's '*properties'. This structure contains various data, like the total number of glyphs and pointers to some mandatory TrueType tables. (See the definition of TT_Face_Properties in section I.) .................................................................. TT_Close_Face( TT_Face face ); Close a given 'face' object. This function will also destroy all the face's child instances. The face's glyphs won't be destroyed, however. .................................................................. TT_New_Instance( TT_Face face, TT_Instance* instance ); Create a new instance object related to the 'face' object. A handle to the newly created instance is returned in 'instance'. The default instance resolution is 96dpi in both vertical and horizontal direction; the default point size is 10pt. .................................................................. TT_Set_Instance_Resolution( TT_Instance instance, int x_resolution, int y_resolution ); Set the target device resolution for a given instance. The values are expressed in dots per inch (dpi). A value of 96dpi is typical for an SVGA display, 72dpi for a Macintosh one, and 300 to 6000dpi for printers. .................................................................. TT_Set_Instance_PointSize( TT_Instance instance, int pointsize ); Sets the point size for a given instance. The size is expressed in 'points', where 1 point = 1/72 inch. The default value is 10pt. .................................................................. TT_Set_Instance_Transform_Flags( TT_Instance instance, int rotated, int stretched ); Set the transform flags for a given instance. These flags are passed to the interpreter each time a glyph is loaded within the instance. Their role is to notify the glyph hinting mechanism that the resulting glyph will be transformed in a special way. Setting one of these flags to true usually disables hinting, though this behaviour varies with each font file. NOTE: The glyph loader doesn't perform the rotation or the stretching itself; this must be done explicitly by the client application. Use the function TT_Apply_Outline_Matrix() for that purpose. .................................................................. TT_Get_Instance_Metrics( TT_Instance instance, TT_Instance_Metrics* imetrics ); This call returns a given instance's current metrics. They are returned in the 'imetrics' structure, which contains, among other things, the current point size, ppem, and device resolution (horizontal and vertical). .................................................................. TT_Done_Instance( TT_Instance instance ); Close a given instance object, destroying its associated data. Note that this is performed automatically when a face is closed on all its child instances. However, explicit deallocation can help in freeing the memory used by the application earlier. .................................................................. TT_New_Glyph( TT_Face face, TT_Glyph* glyph ); Create a new glyph container for the glyphs of the font described by the 'face' handle. A pointer to the container is returned in 'glyph'. The face is said to be the glyph's parent. Note that a glyph isn't destroyed when the face object is destroyed. You have to discard it manually through a call to TT_Done_Glyph(), or automatically when closing the engine through TT_Done_FreeType(). .................................................................. TT_Done_Glyph( TT_Glyph glyph ); Discard a glyph container. This is also done automatically for all glyphs when closing the engine. .................................................................. TT_Load_Glyph( TT_Instance instance, TT_Glyph glyph, int glyph_index, int load_flags ); Load and process (scale and/or hint) a glyph at a given 'instance' into the 'glyph' container. Note that 'glyph' and 'instance' must have the _same_ parent face object, or an error message will be returned. 'glyph_index' is the glyph's index as found in the TrueType file. It is _not_ a character code (see the charmap functions below). 'load_flags' is an integer that specifies which operations are to be performed on the loaded glyph. The following values/bits are used: TTLOAD_SCALE_GLYPH Indicates that the glyph must be scaled to the instance's resolution. The pixel coordinates returned in the glyph outline structure (see below) are then expressed in fractional pixels represented in the 26.6 fixed point floating format defined by Apple as 'F26Dot6'. If scaling is disabled, the coordinates returned in the outline structure are integers, also called 'FUnits' by the TrueType specification. TTLOAD_HINT_GLYPH This flag is only valid when scaling is on. It informs the loader that the glyph must be hinted (i.e. grid-fitted for optimal display). Note that hinting will occur only if the instance's transformations and metrics allow it (for example, most font programs disable hinting automatically in case of rotation or stretching). NOTE: You can also use the constant TTLOAD_DEFAULT, which is simply the union of TTLOAD_SCALE_GLYPH and TTLOAD_HINT_GLYPH for most 'typical' loads. .................................................................. TT_Get_Glyph_Outline( TT_Glyph glyph, TT_Glyph_Outline* outline ); This call returns the glyph's 'outline'. This is a simple structure which contains pointers to the data used to describe an outline to the rasterizer. See the definition of TT_Glyph_Outline() in section I. .................................................................. TT_Get_Glyph_Metrics( TT_Glyph glyph, TT_Glyph_Metrics* metrics ); Extract the glyph's metrics and copy them to the '*metrics' structure. Its format is described in section I. When the glyph has been loaded without scaling, the values are expressed in FUnits (integers relative to the original font grid called the EM Square). When the glyph has been loaded _with_ scaling, which is the default, the values are expressed in fractional pixels in the 26.6 fixed point float format called F26Dot6 (where 1 unit = 1/64th of a pixel). .................................................................. TT_Get_Glyph_Bitmap( TT_Glyph glyph, TT_Raster_Map* bitmap, TT_F26Dot6 x_offset, TT_F26Dot6 y_offset ); This call converts the vectorial glyph representation contained in the object handled by 'glyph' into a bitmap. The target bitmap is described by the 'bitmap' pointer. Clipping will be done if necessary. You can also specify an offset to be applied before the scan-line conversion; 'x_offset' and 'y_offset' must be expressed in fractional pixels (where 1 unit = 1/64th pixel). NOTE1: Choosing non integer pixel offsets, i.e., values of 'x_offset' and 'y_offset' that are not multiples of 64, will ruin the hinting performed by the interpreter, and result in bad rendering at small sizes. NOTE2: The glyph's point coordinates must be scaled before calling this function. Never call this function with a glyph that were loaded with no scaling! .................................................................. TT_Get_Glyph_Pixmap( TT_Glyph glyph, TT_Raster_Map* pixmap, TT_F26Dot6 x_offset, TT_F26Dot6 y_offset ); This call converts the vectorial glyph representation contained in the object handled by 'glyph' into a pixmap (i.e., an 8-bit/pixel map). The result is an anti-aliased version of the glyph (a.k.a. font-smoothing). The target pixmap is described by the 'pixmap' pointer. Note that its width _must_ be a multiple of 4. For a pixmap definition and description, see Section I. As with TT_Get_Glyph_Bitmap(), you can specify offsets to be applied before the rendering ('x_offset' and 'y_offset' must be expressed in fractional pixel coordinates). NOTE1: You don't need to supply a temporary bitmap for the anti-aliaser. The rasterizer uses its own scheme to optimize memory uses. NOTE2: The glyph's point coordinates must be scaled before calling this function. This means that you should never call it with a glyph which has been loaded without scaling! .................................................................. TT_Apply_Outline_Matrix( TT_Glyph_Outline* outline, TT_Matrix* matrix ); Apply a simple transformation matrix on a given outline. This will multiply each point coordinate vector by a 2x2 matrix, which coefficients are written in the 16.16 fixed float format. Rotation can be performed with this function. NOTE: This function takes an outline, and not a glyph handle, as a parameter. This 'feature' lets you apply transformations on your own copies of glyphs. .................................................................. TT_Apply_Outline_Translation( TT_Glyph_Outline* outline, TT_F26Dot6 x_offset, TT_F26Dot6 y_offset ); Apply a simple translation on a given outline. NOTE: This function takes an outline, and not a glyph handle, as a parameter. This 'feature' lets you apply translation to your own copies of glyphs. .................................................................. int TT_Get_CharMap_Count( TT_Face face ); ^^^ Return the number of character mappings present in the TrueType file described by the 'face' handle. Returns zero if there are no mappings, and -1 when the handle is invalid. .................................................................. TT_Get_CharMap_ID( TT_Face face, int charmapIndex, short* platformID, short* encodingID ); Return the platform ID and platform-specific encoding ID for the charmap numbered 'charmapIndex' in the 'face' object. The total number of character mapping tables is returned by the TT_Get_CharMap_Count() function described above. .................................................................. TT_Get_CharMap( TT_Face face, int charmapIndex, TT_CharMap* charMap ); Return a handle for the character map number 'charmapIndex' of 'face'. The handle is placed in '*charMap' and can be used later for fast lookup with the TT_Char_Index() API. Charmap objects are automatically destroyed when their face object is destroyed. .................................................................. int TT_Char_Index( TT_CharMap charMap, ^^^ int charCode ); Apply a charMap to translate a charCode into a glyph index that can be used to load and address a glyph in the TrueType file. The charmap handle can be obtained with TT_Get_CharMap(). .................................................................. int TT_Get_Name_Count( TT_Face face ); ^^^ Returns the number of name strings found in a face's name table. This function will return zero when there are no name strings in the font file, and -1 if the face handle is invalid. .................................................................. TT_Get_Name_ID( TT_Face face, int nameIndex, short* platformID, short* encodingID, short* languageID, short* nameID ); Return the ID of a given name string, indexed by the number 'nameIndex' in a given face. The name index ranges from 0 to the value returned by TT_Get_Name_Count() minus one. Each string has a platformID, encodingID, languageID and nameID, as defined by the TT specification. The platformID is typically in the 0..3 range. Some font files have invalid name table entries; these can be detected from their platformID which is over 3. .................................................................. TT_Get_Name_String( TT_Face face, int nameIndex, char** stringPtr, int* length ); Return a name string's address and length. Note that an invalid name table entry, detected by a platformID > 3, always returns NULL for 'stringPtr' and a zero length. Note: the string belongs to the face object, and should not be written to or freed by the client application. .................................................................. TT_Get_Kerning_Directory( TT_Face face, TT_Kerning* directory ); Queries the kerning directory found in a face object. If no kerning table is found in the TrueType file, the error TT_Err_Table_Is_Missing will be returned. You can access the subtables through the pointers of the directory. However, by default, the directory is only loaded when a face object is created. You must load the subtables that interest you with a call to TT_Load_Kerning_Table(). The layout of all kerning structures is defined in the file "lib/extend/apikern.h". Both formats (0 and 2) are exposed by this API. .................................................................. TT_Load_Kerning_Table( TT_Face face, int kern_index ); Load the kerning subtable number 'kern_index' into memory. The subtable can be accessed through the pointers provided by the kerning directory, obtained from a call to TT_Get_Kerning_Directory(). Note that the interpretation of the kerning data is left to the client application. Read the TrueType specification for more information on kerning encoding. III. Error Messages: Most functions return an error code, typed to TT_Error. A return value of zero indicates no error. The error values are defined in the file 'freetype.h'. Error Unprefixed Error Code Macro Name Description ------------------------------------------------------------------ 0x0000 Ok Successful function call. Always 0! ----------------- high-level API error codes --------------------- The following error codes are returned by the high-level API to indicate an invalid client request. 0x0001 Invalid_Face_Handle An invalid face object handle was passed to an API function. 0x0002 Invalid_Instance_Handle An invalid instance object handle was passed to an API function. 0x0003 Invalid_Glyph_Handle An invalid glyph container handle was passed to an API function. 0x0004 Invalid_CharMap_Handle An invalid charmap handle was passed to an API function. 0x0005 Invalid_Result_Address An output parameter (a result) was given a NULL address in an API call. 0x0006 Invalid_Glyph_Index An invalid glyph index was passed to one API function 0x0007 Invalid_Argument An invalid argument was passed to one API function. Usually, this means a simple out-of-bounds error. 0x0008 Could_Not_Open_File The pathname passed doesn't point to an existing or accessible file. 0x0009 File_Is_Not_Collection Returned by TT_Open_Collection when trying to open a file which isn't a collection. 0x000A Table_Missing A mandatory TrueType table is missing from the font file. Denotes a broken font file. 0x000B Invalid_Horiz_Metrics The font's HMTX table is broken. Denotes a broken font. 0x000C Invalid_CharMap_Format A font's charmap entry has an invalid format. Some other entries may be valid though. 0x0010 Invalid_File_Format The file isn't a TrueType font or collection ----------------- memory component error codes ------------------- 0x0100 Out_Of_Memory An operation couldn't be performed due to memory exhaustion. ----------------- file component error codes --------------------- 0x0200 Invalid_File_Offset Trying to seek to an invalid portion of the font file. Denotes a broken file. 0x0201 Invalid_File_Read Trying to read an invalid portion of the font file. Denotes a broken file. 0x0202 Invalid_Frame_Access Trying to frame an invalid portion of the font file. Denotes a broken file. ----------------- glyph loader error codes ----------------------- These errors are produced by the glyph loader. They denote an invalid glyph record within the font file. 0x0300 Too_Many_Points The glyph has too many points to be valid for its font file. 0x0301 Too_Many_Contours The glyph has too many contours to be valid for its font file. 0x0302 Invalid_Composite_Glyph A composite glyph's description is broken. 0x0303 Too_Many_Ins The glyph has too many instructions to be valid for its font file. ----------------- byte-code interpreter error codes -------------- These error codes are produced by the TrueType byte-code interpreter. They usually indicate a broken font file or a broken glyph within a font. 0x0400 Invalid_Opcode Found an invalid opcode in a TrueType byte-code stream. 0x0401 Too_Few_Arguments An opcode was invoked with too few arguments on the stack. 0x0402 Stack_Overflow The interpreter's stack has been filled up and operations can't continue. 0x0403 Code_Overflow The byte-code stream runs out of its valid bounds. 0x0404 Bad_Argument A function received an invalid argument. 0x0405 Divide_By_Zero A division by 0 operation was queried by the interpreter program. 0x0406 Storage_Overflow The program tried to access data outside of its storage area. 0x0407 Cvt_Overflow The program tried to access data outside of its control value table. 0x0408 Invalid_Reference The program tried to reference an invalid point, zone or contour. 0x0409 Invalid_Distance The program tried to use an invalid distance. 0x040A Interpolate_Twilight The program tried to interpolate twilight points. 0x040B Debug_Opcode The now invalid 'debug' opcode was found in the byte-code stream. 0x040C ENDF_In_Exec_Stream A misplaced ENDF was encountered in the byte-code stream. 0x040D Out_Of_CodeRanges The program tried to allocate too much code ranges (this is really an engine internal error that should never happen). 0x040E Nested_DEFS Nested function definitions encountered. 0x040F Invalid_CodeRange The program tried to access an invalid code range. ----------------- internal failure error codes ------------------- These error codes are produced if an incoherent library state has been detected. All of these reflect a severe bug in the engine (or a severe memory corruption due to massive overwrites by your application into the library's data)! If you do encounter a font that makes one of the test programs produce such an error, please report it! 0x0500 Nested_Frame_Access 0x0501 Invalid_Cache_List 0x0502 Could_Not_Find_Context 0x0503 Unlisted_Object ----------------- scan-line converter error codes ---------------- These error codes are produced by the raster component. They indicate that an outline structure was incoherently set up, or that you're trying to render a horribly complex glyph. They should be _extremely_ rare, however. 0x0600 Raster_Pool_Overflow Render pool overflow. This should never happen in this release. 0x0601 Raster_Negative_Height A negative height was produced. 0x0602 Raster_Invalid_Value The outline data wasn't set properly. Check that: points >= endContours[contours] 0x0603 Raster_Not_Initialized You did not call TT_Init_FreeType! ----------------- engine extensions error codes ------------------ The engine's extensions also provide their own error codes, within their own group: 0x0A00 Invalid_Kerning_Table_Format A kerning subtable format was found invalid in this font. --- end of apiref.txt ---