path: root/src/sdf/ftsdf.c

#include <freetype/internal/ftobjs.h>
#include <freetype/internal/ftdebug.h>
#include <freetype/fttrigon.h>
#include "ftsdf.h"

#include "ftsdferrs.h"

  /**************************************************************************
   *
   * for tracking memory used
   *
   */

#ifdef FT_DEBUG_LEVEL_TRACE

  #undef FT_DEBUG_INNER
  #undef FT_ASSIGNP_INNER

  #define FT_DEBUG_INNER( exp )  ( _ft_debug_file   = __FILE__, \
                                   _ft_debug_lineno = line,     \
                                   (exp) )

  #define FT_ASSIGNP_INNER( p, exp )  ( _ft_debug_file   = __FILE__, \
                                        _ft_debug_lineno = line,     \
                                        FT_ASSIGNP( p, exp ) )

  /* To be used with `FT_Memory::user' in order to track */
  /* memory allocations.                                 */
  typedef struct  SDF_MemoryUser_
  {
    void*    prev_user;
    FT_Long  total_usage;

  } SDF_MemoryUser;

  /* Use these functions while allocating and deallocating  */
  /* memory. These macros restore the previous user pointer */
  /* before calling the allocation functions, which is ess- */
  /* ential if the program is compiled with macro           */
  /* `FT_DEBUG_MEMORY'.                                     */

  static FT_Pointer
  sdf_alloc( FT_Memory  memory,
             FT_Long    size,
             FT_Error*  err, 
             FT_Int     line )
  {
    SDF_MemoryUser*  current_user;
    FT_Pointer       ptr;
    FT_Error         error;


    current_user = (SDF_MemoryUser*)memory->user;
    memory->user = current_user->prev_user;

    if ( !FT_QALLOC( ptr, size ) )      
      current_user->total_usage += size;

    memory->user = (void*)current_user;
    *err = error;

    return ptr;
  }

  static void
  sdf_free( FT_Memory    memory,
             FT_Pointer  ptr,
             FT_Int      line )
  {
    SDF_MemoryUser*  current_user;

    current_user = (SDF_MemoryUser*)memory->user;
    memory->user = current_user->prev_user;

    FT_FREE( ptr );

    memory->user = (void*)current_user;
  }

  #define SDF_ALLOC( ptr, size )                     \
            ( ptr = sdf_alloc( memory, size,         \
                               &error, __LINE__ ),   \
              error != 0 )

  #define SDF_FREE( ptr )                            \
            sdf_free( memory, ptr, __LINE__ )        \

  #define SDF_MEMORY_TRACKER_DECLARE() SDF_MemoryUser  sdf_memory_user

  #define SDF_MEMORY_TRACKER_SETUP()                    \
            sdf_memory_user.prev_user   = memory->user; \
            sdf_memory_user.total_usage = 0;            \
            memory->user = &sdf_memory_user

  #define SDF_MEMORY_TRACKER_DONE()                     \
            memory->user = sdf_memory_user.prev_user;   \
            FT_TRACE0(( "[sdf] sdf_raster_render: "     \
                        "Total memory used = %ld\n",    \
                         sdf_memory_user.total_usage ))

#else

  /* Use the native allocation functions. */
  #define SDF_ALLOC FT_QALLOC
  #define SDF_FREE  FT_FREE

  /* Do nothing */
  #define SDF_MEMORY_TRACKER_DECLARE() FT_DUMMY_STMNT
  #define SDF_MEMORY_TRACKER_SETUP()   FT_DUMMY_STMNT
  #define SDF_MEMORY_TRACKER_DONE()    FT_DUMMY_STMNT

#endif

  /**************************************************************************
   *
   * definitions
   *
   */

  /* If it is defined to 1 then the rasterizer will use Newton-Raphson's  */
  /* method for finding shortest distance from a point to a conic curve.  */
  /* The other method is an analytical method which find the roots of a   */
  /* cubic polynomial to find the shortest distance. But the analytical   */
  /* method has underflow as of now. So, use the Newton's method if there */
  /* is any visible artifacts.                                            */
  #ifndef USE_NEWTON_FOR_CONIC
  #  define USE_NEWTON_FOR_CONIC 1
  #endif

  /* `MAX_NEWTON_DIVISIONS' is the number of intervals the bezier curve   */
  /* is sampled and checked for shortest distance.                        */
  #define MAX_NEWTON_DIVISIONS   4

  /* `MAX_NEWTON_STEPS' is the number of steps of Newton's iterations in  */
  /* each interval of the bezier curve. Basically for each division we    */
  /* run the Newton's approximation (i.e. x -= Q( t ) / Q'( t )) to get   */
  /* the shortest distance.                                               */
  #define MAX_NEWTON_STEPS       4

  /* This is the distance in 16.16 which is used for corner resolving. If */
  /* the difference of two distance is less than `CORNER_CHECK_EPSILON'   */
  /* then they will be checked for corner if they have ambiguity.         */
  #define CORNER_CHECK_EPSILON   32

  #if 0

  /* Coarse grid dimension. Probably will be removed in the future cause  */
  /* coarse grid optimization is the slowest.                             */
  #define CG_DIMEN               8

  #endif

  /**************************************************************************
   *
   * macros
   *
   */

  #define MUL_26D6( a, b ) ( ( ( a ) * ( b ) ) / 64 )
  #define VEC_26D6_DOT( p, q ) ( MUL_26D6( p.x, q.x ) +   \
                                 MUL_26D6( p.y, q.y ) )

  /**************************************************************************
   *
   * structures and enums
   *
   */

  /**************************************************************************
   *
   * @Struct:
   *   SDF_TRaster
   *
   * @Description:
   *   This struct is used in place of `FT_Raster' and is stored within
   *   the internal freetype renderer struct. While rasterizing this is
   *   passed to the `FT_Raster_Render_Func' function, which then can be
   *   used however we want.
   *
   * @Fields:
   *   memory ::
   *     Used internally to allocate intermediate memory while raterizing.
   *
   */
  typedef struct  SDF_TRaster_
  {
    FT_Memory  memory;

  } SDF_TRaster;

  /**************************************************************************
   *
   * @Enum:
   *   SDF_Edge_Type
   *
   * @Description:
   *   Enumeration of all the types of curve present in fonts.
   *
   * @Fields:
   *   SDF_EDGE_UNDEFINED ::
   *     Undefined edge, simply used to initialize and detect errors.
   *
   *   SDF_EDGE_LINE ::
   *     Line segment with start and end point.
   *
   *   SDF_EDGE_CONIC ::
   *     A conic/quadratic bezier curve with start, end and on control
   *     point.
   *
   *   SDF_EDGE_CUBIC ::
   *     A cubic bezier curve with start, end and two control points.
   *
   */
  typedef enum  SDF_Edge_Type_
  {
    SDF_EDGE_UNDEFINED  = 0,
    SDF_EDGE_LINE       = 1,
    SDF_EDGE_CONIC      = 2,
    SDF_EDGE_CUBIC      = 3

  } SDF_Edge_Type;

  /**************************************************************************
   *
   * @Enum:
   *   SDF_Contour_Orientation
   *
   * @Description:
   *   Enumeration of all the orientation of a contour. We determine the
   *   orientation by calculating the area covered by a contour.
   *
   * @Fields:
   *   SDF_ORIENTATION_NONE ::
   *     Undefined orientation, simply used to initialize and detect errors.
   *
   *   SDF_ORIENTATION_CW ::
   *     Clockwise orientation. (positive area covered)
   *
   *   SDF_ORIENTATION_ACW ::
   *     Anti-clockwise orientation. (negative area covered)
   *
   * @Note:
   *   The orientation is independent of the fill rule of a `FT_Outline',
   *   that means the fill will be different for different font formats.
   *   For example, for TrueType fonts clockwise contours are filled, while
   *   for OpenType fonts anti-clockwise contours are filled. To determine
   *   the propert fill rule use `FT_Outline_Get_Orientation'.
   *
   */
  typedef enum  SDF_Contour_Orientation_
  {
    SDF_ORIENTATION_NONE  = 0,
    SDF_ORIENTATION_CW    = 1,
    SDF_ORIENTATION_ACW   = 2

  } SDF_Contour_Orientation;

  /**************************************************************************
   *
   * @Enum:
   *   SDF_Edge
   *
   * @Description:
   *   Represent an edge of a contour.
   *
   * @Fields:
   *   start_pos ::
   *     Start position of an edge. Valid for all types of edges.
   *
   *   end_pos ::
   *     Etart position of an edge. Valid for all types of edges.
   *
   *   control_a ::
   *     A control point of the edge. Valid only for `SDF_EDGE_CONIC'
   *     and `SDF_EDGE_CUBIC'.
   *
   *   control_b ::
   *     Another control point of the edge. Valid only for `SDF_EDGE_CONIC'.
   *
   *   edge_type ::
   *     Type of the edge, see `SDF_Edge_Type' for all possible edge types.
   *
   *   next ::
   *     Used to create a singly linked list, which can be interpreted
   *     as a contour.
   *
   */
  typedef struct  SDF_Edge_
  {
    FT_26D6_Vec    start_pos;
    FT_26D6_Vec    end_pos;
    FT_26D6_Vec    control_a;
    FT_26D6_Vec    control_b;

    SDF_Edge_Type  edge_type;

    struct SDF_Edge_*   next;

  } SDF_Edge;

  /**************************************************************************
   *
   * @Enum:
   *   SDF_Contour
   *
   * @Description:
   *   Represent a complete contour, which contains a list of edges.
   *
   * @Fields:
   *   last_pos ::
   *     Contains the position of the `end_pos' of the last edge
   *     in the list of edges. Useful while decomposing the outline
   *     using `FT_Outline_Decompose'.
   *
   *   edges ::
   *     Linked list of all the edges that make the contour.
   *
   *   next ::
   *     Used to create a singly linked list, which can be interpreted
   *     as a complete shape or `FT_Outline'.
   *
   */
  typedef struct  SDF_Contour_
  {
    FT_26D6_Vec           last_pos;
    SDF_Edge*             edges;

    struct SDF_Contour_*  next;

  } SDF_Contour;

  /**************************************************************************
   *
   * @Enum:
   *   SDF_Shape
   *
   * @Description:
   *   Represent a complete shape which is the decomposition of `FT_Outline'.
   *
   * @Fields:
   *   memory ::
   *     Used internally to allocate memory.
   *
   *   contours ::
   *     Linked list of all the contours that make the shape.
   *
   */
  typedef struct  SDF_Shape_
  {
    FT_Memory     memory;
    SDF_Contour*  contours;

  } SDF_Shape;

  /**************************************************************************
   *
   * @Enum:
   *   SDF_Signed_Distance
   *
   * @Description:
   *   Represent signed distance of a point, i.e. the distance of the
   *   edge nearest to the point.
   *
   * @Fields:
   *   distance ::
   *     Distance of the point from the nearest edge. Can be squared or
   *     absolute depending on the `USE_SQUARED_DISTANCES' parameter
   *     defined in `ftsdfcommon.h'.
   *
   *   cross ::
   *     Cross product of the shortest distance vector (i.e. the vector
   *     the point to the nearest edge) and the direction of the edge
   *     at the nearest point. This is used to resolve any ambiguity
   *     in the sign.
   *
   *   sign ::
   *     Represent weather the distance vector is outside or inside the
   *     contour corresponding to the edge.
   *
   * @Note:
   *   The `sign' may or may not be correct, therefore it must be checked
   *   properly in case there is an ambiguity.
   *
   */
  typedef struct SDF_Signed_Distance_
  {
    FT_16D16      distance;
    FT_16D16      cross;
    FT_Char       sign;       

  } SDF_Signed_Distance;

  /**************************************************************************
   *
   * @Enum:
   *   SDF_Params
   *
   * @Description:
   *   Yet another internal parameters required by the rasterizer.
   *
   * @Fields:
   *   orientation ::
   *     This is not the `SDF_Contour_Orientation', this is the
   *     `FT_Orientation', which determine weather clockwise is to 
   *     be filled or anti-clockwise.
   *
   *   flip_sign ::
   *     Simply flip the sign if this is true. By default the points
   *     filled by the outline are positive.
   *
   *   flip_y ::
   *     If set to true the output bitmap will be upside down. Can be
   *     useful because OpenGL and DirectX have different coordinate
   *     system for textures.
   *
   *   overload_sign ::
   *     In the subdivision and bounding box optimization, the default
   *     outside sign is taken as -1. This parameter can be used to
   *     modify that behaviour. For example, while generating SDF for
   *     single counter-clockwise contour the outside sign should be 1.
   *
   */
  typedef struct SDF_Params_
  {
    FT_Orientation  orientation;
    FT_Bool         flip_sign;
    FT_Bool         flip_y;

    FT_Int          overload_sign;

  } SDF_Params;

  /**************************************************************************
   *
   * constants, initializer and destructor
   *
   */

  static
  const FT_Vector    zero_vector  = { 0, 0 };

  static
  const SDF_Edge     null_edge    = { { 0, 0 }, { 0, 0 },
                                      { 0, 0 }, { 0, 0 },
                                      SDF_EDGE_UNDEFINED, NULL };

  static
  const SDF_Contour  null_contour = { { 0, 0 }, NULL, NULL };

  static
  const SDF_Shape    null_shape   = { NULL, NULL };

  static
  const SDF_Signed_Distance  max_sdf = { INT_MAX, 0, 0 };

  /* Creates a new `SDF_Edge' on the heap and assigns the `edge' */
  /* pointer to the newly allocated memory.                      */
  static FT_Error
  sdf_edge_new( FT_Memory   memory,
                SDF_Edge**  edge )
  {
    FT_Error   error = FT_Err_Ok;
    SDF_Edge*  ptr   = NULL;


    if ( !memory || !edge )
    {
      error = FT_THROW( Invalid_Argument );
      goto Exit;
    }

    if ( !SDF_ALLOC( ptr, sizeof( *ptr ) ) )
    {
      *ptr = null_edge;
      *edge = ptr;
    }

  Exit:
    return error;
  }

  /* Frees the allocated `edge' variable. */
  static void
  sdf_edge_done( FT_Memory   memory,
                 SDF_Edge**  edge )
  {
    if ( !memory || !edge || !*edge )
      return;

    SDF_FREE( *edge );
  }

  /* Creates a new `SDF_Contour' on the heap and assigns  */
  /* the `contour' pointer to the newly allocated memory. */
  static FT_Error
  sdf_contour_new( FT_Memory      memory,
                   SDF_Contour**  contour )
  {
    FT_Error      error = FT_Err_Ok;
    SDF_Contour*  ptr   = NULL;


    if ( !memory || !contour )
    {
      error = FT_THROW( Invalid_Argument );
      goto Exit;
    }

    if ( !SDF_ALLOC( ptr, sizeof( *ptr ) ) )
    {
      *ptr = null_contour;
      *contour = ptr;
    }

  Exit:
    return error;
  }

  /* Frees the allocated `contour' variable and also frees */
  /* the list of edges.                                    */
  static void
  sdf_contour_done( FT_Memory      memory,
                    SDF_Contour**  contour )
  {
    SDF_Edge*  edges;
    SDF_Edge*  temp;

    if ( !memory || !contour || !*contour )
      return;

    edges = (*contour)->edges;

    /* release all the edges */
    while ( edges )
    {
      temp = edges;
      edges = edges->next;

      sdf_edge_done( memory, &temp );
    }

    SDF_FREE( *contour );
  }

  /* Creates a new `SDF_Shape' on the heap and assigns  */
  /* the `shape' pointer to the newly allocated memory. */
  static FT_Error
  sdf_shape_new( FT_Memory    memory,
                 SDF_Shape**  shape )
  {
    FT_Error      error = FT_Err_Ok;
    SDF_Shape*    ptr   = NULL;


    if ( !memory || !shape )
    {
      error = FT_THROW( Invalid_Argument );
      goto Exit;
    }

    if ( !SDF_ALLOC( ptr, sizeof( *ptr ) ) )
    {
      *ptr = null_shape;
      ptr->memory = memory;
      *shape = ptr;
    }

  Exit:
    return error;
  }

  /* Frees the allocated `shape' variable and also frees */
  /* the list of contours.                               */
  static void
  sdf_shape_done( SDF_Shape**  shape )
  {
    FT_Memory     memory;
    SDF_Contour*  contours;
    SDF_Contour*  temp;


    if ( !shape || !*shape )
      return;

    memory = (*shape)->memory;
    contours = (*shape)->contours;

    if ( !memory )
      return;

    /* release all the contours */
    while ( contours )
    {
      temp = contours;
      contours = contours->next;

      sdf_contour_done( memory, &temp );
    }

    /* release the allocated shape struct  */
    SDF_FREE( *shape );
  }

/* END */