FreeType » Docs » Miscellaneous » TrueTypeGX/AAT Validation

TrueTypeGX/AAT Validation¶

Synopsis¶

This section contains the declaration of functions to validate some TrueTypeGX tables (feat, mort, morx, bsln, just, kern, opbd, trak, prop, lcar).

FT_TrueTypeGX_Validate¶

Defined in FT_GX_VALIDATE_H (freetype/ftgxval.h).

  FT_EXPORT( FT_Error )
  FT_TrueTypeGX_Validate( FT_Face   face,
                          FT_UInt   validation_flags,
                          FT_Bytes  tables[FT_VALIDATE_GX_LENGTH],
                          FT_UInt   table_length );

Validate various TrueTypeGX tables to assure that all offsets and indices are valid. The idea is that a higher-level library that actually does the text layout can access those tables without error checking (which can be quite time consuming).

input

face	A handle to the input face.
validation_flags	A bit field that specifies the tables to be validated. See `FT_VALIDATE_GXXXX` for possible values.
table_length	The size of the `tables` array. Normally, `FT_VALIDATE_GX_LENGTH` should be passed.

output

tables

The array where all validated sfnt tables are stored. The array itself must be allocated by a client.

return

FreeType error code. 0 means success.

note

This function only works with TrueTypeGX fonts, returning an error otherwise.

After use, the application should deallocate the buffers pointed to by each tables element, by calling FT_TrueTypeGX_Free. A NULL value indicates that the table either doesn't exist in the font, the application hasn't asked for validation, or the validator doesn't have the ability to validate the sfnt table.

FT_TrueTypeGX_Free¶

Defined in FT_GX_VALIDATE_H (freetype/ftgxval.h).

  FT_EXPORT( void )
  FT_TrueTypeGX_Free( FT_Face   face,
                      FT_Bytes  table );

Free the buffer allocated by TrueTypeGX validator.

input

face	A handle to the input face.
table	The pointer to the buffer allocated by `FT_TrueTypeGX_Validate`.

note

This function must be used to free the buffer allocated by FT_TrueTypeGX_Validate only.

FT_ClassicKern_Validate¶

Defined in FT_GX_VALIDATE_H (freetype/ftgxval.h).

  FT_EXPORT( FT_Error )
  FT_ClassicKern_Validate( FT_Face    face,
                           FT_UInt    validation_flags,
                           FT_Bytes  *ckern_table );

Validate classic (16-bit format) kern table to assure that the offsets and indices are valid. The idea is that a higher-level library that actually does the text layout can access those tables without error checking (which can be quite time consuming).

The ‘kern’ table validator in FT_TrueTypeGX_Validate deals with both the new 32-bit format and the classic 16-bit format, while FT_ClassicKern_Validate only supports the classic 16-bit format.

input

face	A handle to the input face.
validation_flags	A bit field that specifies the dialect to be validated. See `FT_VALIDATE_CKERNXXX` for possible values.

output

ckern_table

A pointer to the kern table.

return

FreeType error code. 0 means success.

note

After use, the application should deallocate the buffers pointed to by ckern_table, by calling FT_ClassicKern_Free. A NULL value indicates that the table doesn't exist in the font.

FT_ClassicKern_Free¶

Defined in FT_GX_VALIDATE_H (freetype/ftgxval.h).

  FT_EXPORT( void )
  FT_ClassicKern_Free( FT_Face   face,
                       FT_Bytes  table );

Free the buffer allocated by classic Kern validator.

input

face	A handle to the input face.
table	The pointer to the buffer that is allocated by `FT_ClassicKern_Validate`.

note

This function must be used to free the buffer allocated by FT_ClassicKern_Validate only.

FT_VALIDATE_GX_LENGTH¶

Defined in FT_GX_VALIDATE_H (freetype/ftgxval.h).

#define FT_VALIDATE_GX_LENGTH  ( FT_VALIDATE_GX_LAST_INDEX + 1 )

The number of tables checked in this module. Use it as a parameter for the table-length argument of function FT_TrueTypeGX_Validate.

FT_VALIDATE_GXXXX¶

Defined in FT_GX_VALIDATE_H (freetype/ftgxval.h).

#define FT_VALIDATE_feat  FT_VALIDATE_GX_BITFIELD( feat )
#define FT_VALIDATE_mort  FT_VALIDATE_GX_BITFIELD( mort )
#define FT_VALIDATE_morx  FT_VALIDATE_GX_BITFIELD( morx )
#define FT_VALIDATE_bsln  FT_VALIDATE_GX_BITFIELD( bsln )
#define FT_VALIDATE_just  FT_VALIDATE_GX_BITFIELD( just )
#define FT_VALIDATE_kern  FT_VALIDATE_GX_BITFIELD( kern )
#define FT_VALIDATE_opbd  FT_VALIDATE_GX_BITFIELD( opbd )
#define FT_VALIDATE_trak  FT_VALIDATE_GX_BITFIELD( trak )
#define FT_VALIDATE_prop  FT_VALIDATE_GX_BITFIELD( prop )
#define FT_VALIDATE_lcar  FT_VALIDATE_GX_BITFIELD( lcar )

#define FT_VALIDATE_GX  ( FT_VALIDATE_feat | \
                          FT_VALIDATE_mort | \
                          FT_VALIDATE_morx | \
                          FT_VALIDATE_bsln | \
                          FT_VALIDATE_just | \
                          FT_VALIDATE_kern | \
                          FT_VALIDATE_opbd | \
                          FT_VALIDATE_trak | \
                          FT_VALIDATE_prop | \
                          FT_VALIDATE_lcar )

A list of bit-field constants used with FT_TrueTypeGX_Validate to indicate which TrueTypeGX/AAT Type tables should be validated.

values

FT_VALIDATE_feat	Validate ‘feat’ table.
FT_VALIDATE_mort	Validate ‘mort’ table.
FT_VALIDATE_morx	Validate ‘morx’ table.
FT_VALIDATE_bsln	Validate ‘bsln’ table.
FT_VALIDATE_just	Validate ‘just’ table.
FT_VALIDATE_kern	Validate ‘kern’ table.
FT_VALIDATE_opbd	Validate ‘opbd’ table.
FT_VALIDATE_trak	Validate ‘trak’ table.
FT_VALIDATE_prop	Validate ‘prop’ table.
FT_VALIDATE_lcar	Validate ‘lcar’ table.
FT_VALIDATE_GX	Validate all TrueTypeGX tables (feat, mort, morx, bsln, just, kern, opbd, trak, prop and lcar).

FT_VALIDATE_CKERNXXX¶

Defined in FT_GX_VALIDATE_H (freetype/ftgxval.h).

#define FT_VALIDATE_MS     ( FT_VALIDATE_GX_START << 0 )
#define FT_VALIDATE_APPLE  ( FT_VALIDATE_GX_START << 1 )

#define FT_VALIDATE_CKERN  ( FT_VALIDATE_MS | FT_VALIDATE_APPLE )

A list of bit-field constants used with FT_ClassicKern_Validate to indicate the classic kern dialect or dialects. If the selected type doesn't fit, FT_ClassicKern_Validate regards the table as invalid.

values

FT_VALIDATE_MS	Handle the ‘kern’ table as a classic Microsoft kern table.
FT_VALIDATE_APPLE	Handle the ‘kern’ table as a classic Apple kern table.
FT_VALIDATE_CKERN	Handle the ‘kern’ as either classic Apple or Microsoft kern table.