ftbbox.c

Qt/Embedded是一个多平台的C++图形用户界面应用程序框架

/***************************************************************************/
/*                                                                         */
/*  ftbbox.c                                                               */
/*                                                                         */
/*    FreeType bbox computation (body).                                    */
/*                                                                         */
/*  Copyright 1996-2000 by                                                 */
/*  David Turner, Robert Wilhelm, and Werner Lemberg.                      */
/*                                                                         */
/*  This file is part of the FreeType project, and may only be used        */
/*  modified and distributed under the terms of the FreeType project       */
/*  license, LICENSE.TXT.  By continuing to use, modify, or distribute     */
/*  this file you indicate that you have read the license and              */
/*  understand and accept it fully.                                        */
/*                                                                         */
/***************************************************************************/

  /*************************************************************************/
  /*                                                                       */
  /* This component has a _single_ role: to compute exact outline bounding */
  /* boxes.                                                                */
  /*                                                                       */
  /* It is separated from the rest of the engine for various technical     */
  /* reasons.  It may well be integrated in `ftoutln' later.               */
  /*                                                                       */
  /*************************************************************************/


#include <ftbbox.h>
#include <ftimage.h>
#include <ftobjs.h>

  typedef struct  TBBox_Rec_
  {
    FT_Vector  last;
    FT_BBox    bbox;

  } TBBox_Rec;


  /*************************************************************************/
  /*                                                                       */
  /* <Function>                                                            */
  /*    BBox_Move_To                                                       */
  /*                                                                       */
  /* <Description>                                                         */
  /*    This function is used as a `move_to' and `line_to' emitter during  */
  /*    FT_Raster_Decompose().  It simply records the destination point in */
  /*    `user->last'.                                                      */
  /*                                                                       */
  /* <Input>                                                               */
  /*    to   :: A pointer to the destination vector.                       */
  /*                                                                       */
  /* <InOut>                                                               */
  /*    user :: A pointer to the current walk context.                     */
  /*                                                                       */
  /* <Return>                                                              */
  /*    Error code.  0 means success.                                      */
  /*                                                                       */
  static
  int  BBox_Move_To( FT_Vector*  to,
                     TBBox_Rec*  user )
  {
    user->last = *to;

    return 0;
  }


#define CHECK_X( p, bbox )  \
          ( p->x < bbox.xMin || p->x > bbox.xMax )

#define CHECK_Y( p, bbox )  \
          ( p->y < bbox.yMin || p->y > bbox.yMax )


  /*************************************************************************/
  /*                                                                       */
  /* <Function>                                                            */
  /*    BBox_Conic_Check                                                   */
  /*                                                                       */
  /* <Description>                                                         */
  /*    Finds the extrema of a 1-dimensional conic Bezier curve and update */
  /*    a bounding range.  This version uses direct computation, as it     */
  /*    doesn't need square roots.                                         */
  /*                                                                       */
  /* <Input>                                                               */
  /*    y1  :: The start coordinate.                                       */
  /*    y2  :: The coordinate of the control point.                        */
  /*    y3  :: The end coordinate.                                         */
  /*                                                                       */
  /* <InOut>                                                               */
  /*    min :: The address of the current minimum.                         */
  /*    max :: The address of the current maximum.                         */
  /*                                                                       */
  static
  void  BBox_Conic_Check( FT_Pos   y1,
                          FT_Pos   y2,
                          FT_Pos   y3,
                          FT_Pos*  min,
                          FT_Pos*  max )
  {
    if( y1 == y3 )
    {
      if ( y2 == y1 )               /* Flat arc */
      {
        y3 = y1;
        goto Suite;
      }
    }
    else if ( y1 < y3 )
    {
      if ( y2 >= y1 && y2 <= y3 )   /* Ascending arc */
        goto Suite;
    }
    else
    {
      if ( y2 >= y3 && y2 <= y1 )   /* Descending arc */
      {
        y2 = y1;
        y1 = y3;
        y3 = y2;
        goto Suite;
      }
    }

    y1 = y3 = FT_MulDiv( y2 - y1, y2 - y1, y1 - 2*y2 + y3 );

  Suite:
    if ( y1 < *min ) *min = y1;
    if ( y3 > *max ) *max = y3;
  }


  /*************************************************************************/
  /*                                                                       */
  /* <Function>                                                            */
  /*    BBox_Conic_To                                                      */
  /*                                                                       */
  /* <Description>                                                         */
  /*    This function is used as a `conic_to' emitter during               */
  /*    FT_Raster_Decompose().  It checks a conic Bezier curve with the    */
  /*    current bounding box, and computes its extrema if necessary to     */
  /*    update it.                                                         */
  /*                                                                       */
  /* <Input>                                                               */
  /*    control :: A pointer to a control point.                           */
  /*    to      :: A pointer to the destination vector.                    */
  /*                                                                       */
  /* <InOut>                                                               */
  /*    user    :: The address of the current walk context.                */
  /*                                                                       */
  /* <Return>                                                              */
  /*    Error code.  0 means success.                                      */
  /*                                                                       */
  /* <Note>                                                                */
  /*    In the case of a non-monotonous arc, we compute directly the       */
  /*    extremum coordinates, as it is sufficiently fast.                  */
  /*                                                                       */
  static
  int  BBox_Conic_To( FT_Vector*  control,
                      FT_Vector*  to,
                      TBBox_Rec*  user )
  {
    if ( CHECK_X( control, user->bbox ) ||
         CHECK_X( to,      user->bbox ) )

      BBox_Conic_Check( user->last.x,
                        control->x,
                        to->x,
                        &user->bbox.xMin,
                        &user->bbox.xMax );

    if ( CHECK_Y( control, user->bbox ) ||
         CHECK_Y( to,      user->bbox ) )

      BBox_Conic_Check( user->last.y,
                        control->y,
                        to->y,
                        &user->bbox.yMin,
                        &user->bbox.yMax );

    return 0;
  }


  /*************************************************************************/
  /*                                                                       */
  /* <Function>                                                            */
  /*    BBox_Cubic_Check                                                   */
  /*                                                                       */
  /* <Description>                                                         */
  /*    Finds the extrema of a 1-dimensional cubic Bezier curve and        */
  /*    updates a bounding range.  This version uses splitting because we  */
  /*    don't want to use square roots and extra accuracies.               */
  /*                                                                       */
  /* <Input>                                                               */
  /*    p1  :: The start coordinate.                                       */
  /*    p2  :: The coordinate of the first control point.                  */
  /*    p3  :: The coordinate of the second control point.                 */
  /*    p4  :: The end coordinate.                                         */
  /*                                                                       */
  /* <InOut>                                                               */
  /*    min :: The address of the current minimum.                         */
  /*    max :: The address of the current maximum.                         */
  /*                                                                       */
  static
  void  BBox_Cubic_Check( FT_Pos   p1,
                          FT_Pos   p2,
                          FT_Pos   p3,
                          FT_Pos   p4,
                          FT_Pos*  min,
                          FT_Pos*  max )
  {
    FT_Pos  stack[33], *arc;


    arc = stack;

    arc[0] = p1;
    arc[1] = p2;
    arc[2] = p3;
    arc[3] = p4;

    do