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# FreeType-2.4.5 API Reference

# Module Management

## Synopsis

| FT_Module_Constructor |  | FT_Get_Module |  | FT_Set_Debug_Hook
| FT_Module_Destructor |  | FT_Remove_Module |  | FT_Add_Default_Modules
| FT_Module_Requester |  | FT_Reference_Library |  | FT_Renderer_Class
| FT_Module_Class |  | FT_New_Library |  | FT_Get_Renderer
| FT_Add_Module |  | FT_Done_Library |  | FT_Set_Renderer

The definitions below are used to manage modules within FreeType. Modules can be added, upgraded, and removed at runtime.

#### FT_Module_Constructor
Defined in FT_MODULE_H (freetype/ftmodapi.h).
      typedef FT_Error
      (*FT_Module_Constructor)( FT_Module  module );
A function used to initialize (not create) a new module object.
input
module | The module to initialize.

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#### FT_Module_Destructor
Defined in FT_MODULE_H (freetype/ftmodapi.h).
      typedef void
      (*FT_Module_Destructor)( FT_Module  module );
A function used to finalize (not destroy) a given module object.
input
module | The module to finalize.

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#### FT_Module_Requester
Defined in FT_MODULE_H (freetype/ftmodapi.h).
      typedef FT_Module_Interface
      (*FT_Module_Requester)( FT_Module    module,
                              const char*  name );
A function used to query a given module for a specific interface.
input
module | The module to finalize.
name | The name of the interface in the module.

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#### FT_Module_Class
Defined in FT_MODULE_H (freetype/ftmodapi.h).
      typedef struct  FT_Module_Class_
      {
        FT_ULong               module_flags;
        FT_Long                module_size;
        const FT_String*       module_name;
        FT_Fixed               module_version;
        FT_Fixed               module_requires;

        const void*            module_interface;

        FT_Module_Constructor  module_init;
        FT_Module_Destructor   module_done;
        FT_Module_Requester    get_interface;

      } FT_Module_Class;
The module class descriptor.
fields
module_flags | Bit flags describing the module.
module_size | The size of one module object/instance in bytes.
module_name | The name of the module.
module_version | The version, as a 16.16 fixed number (major.minor).
module_requires | The version of FreeType this module requires, as a 16.16 fixed number (major.minor). Starts at version 2.0, i.e., 0x20000.
module_init | The initializing function.
module_done | The finalizing function.
get_interface | The interface requesting function.

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#### FT_Add_Module
Defined in FT_MODULE_H (freetype/ftmodapi.h).
      FT_EXPORT( FT_Error )
      FT_Add_Module( FT_Library              library,
                     const FT_Module_Class*  clazz );
Add a new module to a given library instance.
inout
library | A handle to the library object.
input
clazz | A pointer to class descriptor for the module.
return
FreeType error code. 0 means success.
note
An error will be returned if a module already exists by that name, or if the module requires a version of FreeType that is too great.

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#### FT_Get_Module
Defined in FT_MODULE_H (freetype/ftmodapi.h).
      FT_EXPORT( FT_Module )
      FT_Get_Module( FT_Library   library,
                     const char*  module_name );
Find a module by its name.
input
library | A handle to the library object.
module_name | The module's name (as an ASCII string).
return
A module handle. 0 if none was found.
note
FreeType's internal modules aren't documented very well, and you should look up the source code for details.

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#### FT_Remove_Module
Defined in FT_MODULE_H (freetype/ftmodapi.h).
      FT_EXPORT( FT_Error )
      FT_Remove_Module( FT_Library  library,
                        FT_Module   module );
Remove a given module from a library instance.
inout
library | A handle to a library object.
input
module | A handle to a module object.
return
FreeType error code. 0 means success.
note
The module object is destroyed by the function in case of success.

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#### FT_Reference_Library
Defined in FT_MODULE_H (freetype/ftmodapi.h).
      FT_EXPORT( FT_Error )
      FT_Reference_Library( FT_Library  library );
A counter gets initialized to 1 at the time an FT_Library structure is created. This function increments the counter. FT_Done_Library then only destroys a library if the counter is 1, otherwise it simply decrements the counter. This function helps in managing life-cycles of structures which reference FT_Library objects.
input
library | A handle to a target library object.
return
FreeType error code. 0 means success.
since
2.4.2

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#### FT_New_Library
Defined in FT_MODULE_H (freetype/ftmodapi.h).
      FT_EXPORT( FT_Error )
      FT_New_Library( FT_Memory    memory,
                      FT_Library  *alibrary );
This function is used to create a new FreeType library instance from a given memory object. It is thus possible to use libraries with distinct memory allocators within the same program. Normally, you would call this function (followed by a call to FT_Add_Default_Modules or a series of calls to FT_Add_Module) instead of FT_Init_FreeType to initialize the FreeType library. Don't use FT_Done_FreeType but FT_Done_Library to destroy a library instance.
input
memory | A handle to the original memory object.
output
alibrary | A pointer to handle of a new library object.
return
FreeType error code. 0 means success.
note
See the discussion of reference counters in the description of FT_Reference_Library.

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#### FT_Done_Library
Defined in FT_MODULE_H (freetype/ftmodapi.h).
      FT_EXPORT( FT_Error )
      FT_Done_Library( FT_Library  library );
Discard a given library object. This closes all drivers and discards all resource objects.
input
library | A handle to the target library.
return
FreeType error code. 0 means success.
note
See the discussion of reference counters in the description of FT_Reference_Library.

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#### FT_Set_Debug_Hook
Defined in FT_MODULE_H (freetype/ftmodapi.h).
      FT_EXPORT( void )
      FT_Set_Debug_Hook( FT_Library         library,
                         FT_UInt            hook_index,
                         FT_DebugHook_Func  debug_hook );
Set a debug hook function for debugging the interpreter of a font format.
inout
library | A handle to the library object.
input
hook_index | The index of the debug hook. You should use the values defined in ‘ftobjs.h’, e.g., ‘FT_DEBUG_HOOK_TRUETYPE’.
debug_hook | The function used to debug the interpreter.
note
Currently, four debug hook slots are available, but only two (for the TrueType and the Type 1 interpreter) are defined. Since the internal headers of FreeType are no longer installed, the symbol ‘FT_DEBUG_HOOK_TRUETYPE’ isn't available publicly. This is a bug and will be fixed in a forthcoming release.

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#### FT_Add_Default_Modules
Defined in FT_MODULE_H (freetype/ftmodapi.h).
      FT_EXPORT( void )
      FT_Add_Default_Modules( FT_Library  library );
Add the set of default drivers to a given library object. This is only useful when you create a library object with FT_New_Library (usually to plug a custom memory manager).
inout
library | A handle to a new library object.

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#### FT_Renderer_Class
Defined in FT_RENDER_H (freetype/ftrender.h).
      typedef struct  FT_Renderer_Class_
      {
        FT_Module_Class            root;

        FT_Glyph_Format            glyph_format;

        FT_Renderer_RenderFunc     render_glyph;
        FT_Renderer_TransformFunc  transform_glyph;
        FT_Renderer_GetCBoxFunc    get_glyph_cbox;
        FT_Renderer_SetModeFunc    set_mode;

        FT_Raster_Funcs*           raster_class;

      } FT_Renderer_Class;
The renderer module class descriptor.
fields
root | The root FT_Module_Class fields.
glyph_format | The glyph image format this renderer handles.
render_glyph | A method used to render the image that is in a given glyph slot into a bitmap.
transform_glyph | A method used to transform the image that is in a given glyph slot.
get_glyph_cbox | A method used to access the glyph's cbox.
set_mode | A method used to pass additional parameters.
raster_class | For FT_GLYPH_FORMAT_OUTLINE renderers only. This is a pointer to its raster's class.

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#### FT_Get_Renderer
Defined in FT_RENDER_H (freetype/ftrender.h).
      FT_EXPORT( FT_Renderer )
      FT_Get_Renderer( FT_Library       library,
                       FT_Glyph_Format  format );
Retrieve the current renderer for a given glyph format.
input
library | A handle to the library object.
format | The glyph format.
return
A renderer handle. 0 if none found.
note
An error will be returned if a module already exists by that name, or if the module requires a version of FreeType that is too great. To add a new renderer, simply use FT_Add_Module. To retrieve a renderer by its name, use FT_Get_Module.

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#### FT_Set_Renderer
Defined in FT_RENDER_H (freetype/ftrender.h).
      FT_EXPORT( FT_Error )
      FT_Set_Renderer( FT_Library     library,
                       FT_Renderer    renderer,
                       FT_UInt        num_params,
                       FT_Parameter*  parameters );
Set the current renderer to use, and set additional mode.
inout
library | A handle to the library object.
input
renderer | A handle to the renderer object.
num_params | The number of additional parameters.
parameters | Additional parameters.
return
FreeType error code. 0 means success.
note
In case of success, the renderer will be used to convert glyph images in the renderer's known format into bitmaps. This doesn't change the current renderer for other formats. Currently, only the B/W renderer, if compiled with FT_RASTER_OPTION_ANTI_ALIASING (providing a 5-levels anti-aliasing mode; this option must be set directly in ‘ftraster.c’ and is undefined by default) accepts a single tag ‘pal5’ to set its gray palette as a character string with 5 elements. Consequently, the third and fourth argument are zero normally.

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