typedef struct FT_RasterRec_*  FT_Raster;

A handle (pointer) to a raster object. Each object can be used independently to convert an outline into a bitmap or pixmap.

  typedef struct  FT_Span_
  {
    short           x;
    unsigned short  len;
    unsigned char   coverage;

  } FT_Span;

A structure used to model a single span of gray (or black) pixels when rendering a monochrome or anti-aliased bitmap.

This structure is used by the span drawing callback type named FT_Raster_Span_Func(), which takes the y-coordinate of the span as a parameter.

The coverage value is always between 0 and 255, even if the number of gray levels have been set through FT_Set_Gray_Levels().

  typedef void
  (*FT_Raster_Span_Func)( int       y,
                          int       count,
                          FT_Span*  spans,
                          void*     user );

A function used as a call-back by the anti-aliased renderer in order to let client applications draw themselves the gray pixel spans on each scan line.

This callback allows client applications to directly render the gray spans of the anti-aliased bitmap to any kind of surfaces.

This can be used to write anti-aliased outlines directly to a given background bitmap, and even perform translucency.

Note that the `count' field cannot be greater than a fixed value defined by the FT_MAX_GRAY_SPANS configuration macro in ftoption.h. By default, this value is set to 32, which means that if there are more than 32 spans on a given scanline, the callback will be called several times with the same `y' parameter in order to draw all callbacks.

Otherwise, the callback is only called once per scan-line, and only for those scanlines that do have `gray' pixels on them.

  typedef int
  (*FT_Raster_BitTest_Func)( int    y,
                             int    x,
                             void*  user );

A function used as a call-back by the monochrome scan-converter to test whether a given target pixel is already set to the drawing `color'. These tests are crucial to implement drop-out control per-se the TrueType spec.

1 if the pixel is `set', 0 otherwise.

  typedef void
  (*FT_Raster_BitSet_Func)( int    y,
                            int    x,
                            void*  user );

A function used as a call-back by the monochrome scan-converter to set an individual target pixel. This is crucial to implement drop-out control according to the TrueType specification.

1 if the pixel is `set', 0 otherwise.

  typedef  enum
  {
    ft_raster_flag_default = 0,
    ft_raster_flag_aa      = 1,
    ft_raster_flag_direct  = 2,
    ft_raster_flag_clip    = 4

  } FT_Raster_Flag;

An enumeration to list the bit flags as used in the `flags' field of a FT_Raster_Params structure.

  typedef struct  FT_Raster_Params_
  {
    FT_Bitmap*              target;
    void*                   source;
    int                     flags;
    FT_Raster_Span_Func     gray_spans;
    FT_Raster_Span_Func     black_spans;
    FT_Raster_BitTest_Func  bit_test;
    FT_Raster_BitSet_Func   bit_set;
    void*                   user;
    FT_BBox                 clip_box;

  } FT_Raster_Params;

A structure to hold the arguments used by a raster's render function.

An anti-aliased glyph bitmap is drawn if the ft_raster_flag_aa bit flag is set in the `flags' field, otherwise a monochrome bitmap will be generated.

If the ft_raster_flag_direct bit flag is set in `flags', the raster will call the `gray_spans' callback to draw gray pixel spans, in the case of an aa glyph bitmap, it will call `black_spans', and `bit_test' and `bit_set' in the case of a monochrome bitmap. This allows direct composition over a pre-existing bitmap through user-provided callbacks to perform the span drawing/composition.

Note that the `bit_test' and `bit_set' callbacks are required when rendering a monochrome bitmap, as they are crucial to implement correct drop-out control as defined in the TrueType specification.

  typedef int
  (*FT_Raster_New_Func)( void*       memory,
                         FT_Raster*  raster );

A function used to create a new raster object.

Error code. 0 means success.

The `memory' parameter is a typeless pointer in order to avoid un-wanted dependencies on the rest of the FreeType code. In practice, it is a FT_Memory, i.e., a handle to the standard FreeType memory allocator. However, this field can be completely ignored by a given raster implementation.

  typedef void
  (*FT_Raster_Done_Func)( FT_Raster  raster );

A function used to destroy a given raster object.

  typedef void
  (*FT_Raster_Reset_Func)( FT_Raster       raster,
                           unsigned char*  pool_base,
                           unsigned long   pool_size );

FreeType provides an area of memory called the `render pool', available to all registered rasters. This pool can be freely used during a given scan-conversion but is shared by all rasters. Its content is thus transient.

This function is called each time the render pool changes, or just after a new raster object is created.

Rasters can ignore the render pool and rely on dynamic memory allocation if they want to (a handle to the memory allocator is passed to the raster constructor). However, this is not recommended for efficiency purposes.

  typedef int
  (*FT_Raster_Set_Mode_Func)( FT_Raster      raster,
                              unsigned long  mode,
                              void*          args );

This function is a generic facility to change modes or attributes in a given raster. This can be used for debugging purposes, or simply to allow implementation-specific `features' in a given raster module.

  typedef int
  (*FT_Raster_Render_Func)( FT_Raster          raster,
                            FT_Raster_Params*  params );

Invokes a given raster to scan-convert a given glyph image into a target bitmap.

Error code. 0 means success.

The exact format of the source image depends on the raster's glyph format defined in its FT_Raster_Funcs structure. It can be an FT_Outline or anything else in order to support a large array of glyph formats.

Note also that the render function can fail and return a FT_Err_Unimplemented_Feature error code if the raster used does not support direct composition.

XXX: For now, the standard raster doesn't support direct composition but this should change for the final release (see the files demos/src/ftgrays.c and demos/src/ftgrays2.c for examples of distinct implementations which support direct composition).

  typedef struct  FT_Raster_Funcs_
  {
    FT_Glyph_Format          glyph_format;
    FT_Raster_New_Func       raster_new;
    FT_Raster_Reset_Func     raster_reset;
    FT_Raster_Set_Mode_Func  raster_set_mode;
    FT_Raster_Render_Func    raster_render;
    FT_Raster_Done_Func      raster_done;

  } FT_Raster_Funcs;

A structure used to describe a given raster class to the library.