psblues.c

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Author : Skef Iterum
Date : 2023-12-14 06:59:05
Hash : 8eab5110
Message : [CFF] Extract `BlueValues` as `Fixed` rather than `Int`. This is a follow-up to commit 26a7f047, [cff] Make blend operator work with floats in private dicts. which addressed the 'party baseline' bug. However, the reporting user indicated that the default location and some other points in design space rendered OK, but other points in design space still had problems. The most obvious issue being that the x-heights of lower-case letters did not align; see https://github.com/adobe-fonts/source-serif/issues/121#issuecomment-1773794136 After some analysis we determined that this was due to an interaction between `BlueValue` rounding and the zone-based algorithm. In short, for a point to be considered in a zone it must fall within the bounds of the zone. (There is a slop factor in some cases, but only a very small one.) In the Adobe-contributed side of the code, point values are not integer-rounded, instead they're kept as (some form of) fixed. Rounding just the `BlueValues` means that points that need to be considered within a zone will fall outside of it at some points in design space. The majority of this patch changes the storage and parsing of `BlueValues` to keep them as `FT_Fixed`. No significant code changes were needed because the values are converted to `Fixed` anyway when stored in `CF_BlueRec`. No attempt was made to address problems in the older pshinter code beyond converting the values from `FT_Fixed` to `FT_Short` when copying the private dictionary. (However, as the point values are also rounded in that code, the problem is much less likely to occur, although inconsistency between rounding and truncation could cause an analogous problem.) * include/freetype/internal/cfftypes.h (CFF_PrivateRec): Use `FT_Fixed` for `blue_values`, `other_blues`, `family_blues`, and `family_other_blues`. * src/cff/cffload.c (cff_blend_doBlend): Updated. * src/cff/cffobjs.c (CFF_fixedToInt): New macro. (cff_make_private_dict): Use it. * src/cff/cffparse.h (cff_kind_delta_fixed): New enum value. * src/cff/cffparse.c (do_fixed): Updated. (CFF_FIELD_DELTA, CFF_FIELD_DELTA_FIXED, CFF_DELTA_KIND): New set of macros, replacing `CFF_FIELD_DELTA`. (cff_parser_run): Updated to handle fixed-float deltas. * src/cff/cfftoken.h: Updated to use `CFF_FIELD_DELTA_FIXED` for blue values. * src/psaux/psblues.c (cf2_blueToFixed): Removed, no longer needed. (cf2_blues_init): Updated. * src/pxaux/psft.c, src/pxaux/psft.h (cf2_getBlueValues, cf2_getOtherBlues, cf2_getFamilyBlues, cf2_getFamilyOtherBlues): Updated signatures. * src/psaux/psobjs.c (t1_make_subfont): Updated.

src/psaux/psblues.c

/****************************************************************************
 *
 * psblues.c
 *
 *   Adobe's code for handling Blue Zones (body).
 *
 * Copyright 2009-2014 Adobe Systems Incorporated.
 *
 * This software, and all works of authorship, whether in source or
 * object code form as indicated by the copyright notice(s) included
 * herein (collectively, the "Work") is made available, and may only be
 * used, modified, and distributed under the FreeType Project License,
 * LICENSE.TXT.  Additionally, subject to the terms and conditions of the
 * FreeType Project License, each contributor to the Work hereby grants
 * to any individual or legal entity exercising permissions granted by
 * the FreeType Project License and this section (hereafter, "You" or
 * "Your") a perpetual, worldwide, non-exclusive, no-charge,
 * royalty-free, irrevocable (except as stated in this section) patent
 * license to make, have made, use, offer to sell, sell, import, and
 * otherwise transfer the Work, where such license applies only to those
 * patent claims licensable by such contributor that are necessarily
 * infringed by their contribution(s) alone or by combination of their
 * contribution(s) with the Work to which such contribution(s) was
 * submitted.  If You institute patent litigation against any entity
 * (including a cross-claim or counterclaim in a lawsuit) alleging that
 * the Work or a contribution incorporated within the Work constitutes
 * direct or contributory patent infringement, then any patent licenses
 * granted to You under this License for that Work shall terminate as of
 * the date such litigation is filed.
 *
 * By using, modifying, or distributing the Work you indicate that you
 * have read and understood the terms and conditions of the
 * FreeType Project License as well as those provided in this section,
 * and you accept them fully.
 *
 */


#include "psft.h"
#include <freetype/internal/ftdebug.h>

#include "psblues.h"
#include "pshints.h"
#include "psfont.h"


  /**************************************************************************
   *
   * The macro FT_COMPONENT is used in trace mode.  It is an implicit
   * parameter of the FT_TRACE() and FT_ERROR() macros, used to print/log
   * messages during execution.
   */
#undef  FT_COMPONENT
#define FT_COMPONENT  cf2blues


  FT_LOCAL_DEF( void )
  cf2_blues_init( CF2_Blues  blues,
                  CF2_Font   font )
  {
    /* pointer to parsed font object */
    PS_Decoder*  decoder = font->decoder;

    CF2_Fixed  zoneHeight;
    CF2_Fixed  maxZoneHeight = 0;
    CF2_Fixed  csUnitsPerPixel;

    size_t  numBlueValues;
    size_t  numOtherBlues;
    size_t  numFamilyBlues;
    size_t  numFamilyOtherBlues;

    FT_Fixed*  blueValues;
    FT_Fixed*  otherBlues;
    FT_Fixed*  familyBlues;
    FT_Fixed*  familyOtherBlues;

    size_t     i;
    CF2_Fixed  emBoxBottom, emBoxTop;

#if 0
    CF2_Int  unitsPerEm = font->unitsPerEm;


    if ( unitsPerEm == 0 )
      unitsPerEm = 1000;
#endif

    FT_ZERO( blues );
    blues->scale = font->innerTransform.d;

    cf2_getBlueMetrics( decoder,
                        &blues->blueScale,
                        &blues->blueShift,
                        &blues->blueFuzz );

    cf2_getBlueValues( decoder, &numBlueValues, &blueValues );
    cf2_getOtherBlues( decoder, &numOtherBlues, &otherBlues );
    cf2_getFamilyBlues( decoder, &numFamilyBlues, &familyBlues );
    cf2_getFamilyOtherBlues( decoder, &numFamilyOtherBlues, &familyOtherBlues );

    /*
     * synthetic em box hint heuristic
     *
     * Apply this when ideographic dictionary (LanguageGroup 1) has no
     * real alignment zones.  Adobe tools generate dummy zones at -250 and
     * 1100 for a 1000 unit em.  Fonts with ICF-based alignment zones
     * should not enable the heuristic.  When the heuristic is enabled,
     * the font's blue zones are ignored.
     *
     */

    /* get em box from OS/2 typoAscender/Descender                      */
    /* TODO: FreeType does not parse these metrics.  Skip them for now. */
#if 0
    FCM_getHorizontalLineMetrics( &e,
                                  font->font,
                                  &ascender,
                                  &descender,
                                  &linegap );
    if ( ascender - descender == unitsPerEm )
    {
      emBoxBottom = cf2_intToFixed( descender );
      emBoxTop    = cf2_intToFixed( ascender );
    }
    else
#endif
    {
      emBoxBottom = CF2_ICF_Bottom;
      emBoxTop    = CF2_ICF_Top;
    }

    if ( cf2_getLanguageGroup( decoder ) == 1     &&
         ( numBlueValues == 0                   ||
           ( numBlueValues == 4               &&
             blueValues[0] < emBoxBottom      &&
             blueValues[1] < emBoxBottom      &&
             blueValues[2] > emBoxTop         &&
             blueValues[3] > emBoxTop         ) ) )
    {
      /*
       * Construct hint edges suitable for synthetic ghost hints at top
       * and bottom of em box.  +-CF2_MIN_COUNTER allows for unhinted
       * features above or below the last hinted edge.  This also gives a
       * net 1 pixel boost to the height of ideographic glyphs.
       *
       * Note: Adjust synthetic hints outward by epsilon (0x.0001) to
       *       avoid interference.  E.g., some fonts have real hints at
       *       880 and -120.
       */

      blues->emBoxBottomEdge.csCoord = emBoxBottom - CF2_FIXED_EPSILON;
      blues->emBoxBottomEdge.dsCoord = cf2_fixedRound(
                                         FT_MulFix(
                                           blues->emBoxBottomEdge.csCoord,
                                           blues->scale ) ) -
                                       CF2_MIN_COUNTER;
      blues->emBoxBottomEdge.scale   = blues->scale;
      blues->emBoxBottomEdge.flags   = CF2_GhostBottom |
                                       CF2_Locked |
                                       CF2_Synthetic;

      blues->emBoxTopEdge.csCoord = emBoxTop + CF2_FIXED_EPSILON +
                                    2 * font->darkenY;
      blues->emBoxTopEdge.dsCoord = cf2_fixedRound(
                                      FT_MulFix(
                                        blues->emBoxTopEdge.csCoord,
                                        blues->scale ) ) +
                                    CF2_MIN_COUNTER;
      blues->emBoxTopEdge.scale   = blues->scale;
      blues->emBoxTopEdge.flags   = CF2_GhostTop |
                                    CF2_Locked |
                                    CF2_Synthetic;

      blues->doEmBoxHints = TRUE;    /* enable the heuristic */

      return;
    }

    /* copy `BlueValues' and `OtherBlues' to a combined array of top and */
    /* bottom zones                                                      */
    for ( i = 0; i < numBlueValues; i += 2 )
    {
      blues->zone[blues->count].csBottomEdge = blueValues[i];
      blues->zone[blues->count].csTopEdge    = blueValues[i + 1];

      zoneHeight = SUB_INT32( blues->zone[blues->count].csTopEdge,
                              blues->zone[blues->count].csBottomEdge );

      if ( zoneHeight < 0 )
      {
        FT_TRACE4(( "cf2_blues_init: ignoring negative zone height\n" ));
        continue;   /* reject this zone */
      }

      if ( zoneHeight > maxZoneHeight )
      {
        /* take maximum before darkening adjustment      */
        /* so overshoot suppression point doesn't change */
        maxZoneHeight = zoneHeight;
      }

      /* adjust both edges of top zone upward by twice darkening amount */
      if ( i != 0 )
      {
        blues->zone[blues->count].csTopEdge    += 2 * font->darkenY;
        blues->zone[blues->count].csBottomEdge += 2 * font->darkenY;
      }

      /* first `BlueValue' is bottom zone; others are top */
      if ( i == 0 )
      {
        blues->zone[blues->count].bottomZone =
          TRUE;
        blues->zone[blues->count].csFlatEdge =
          blues->zone[blues->count].csTopEdge;
      }
      else
      {
        blues->zone[blues->count].bottomZone =
          FALSE;
        blues->zone[blues->count].csFlatEdge =
          blues->zone[blues->count].csBottomEdge;
      }

      blues->count += 1;
    }

    for ( i = 0; i < numOtherBlues; i += 2 )
    {
      blues->zone[blues->count].csBottomEdge = otherBlues[i];
      blues->zone[blues->count].csTopEdge    = otherBlues[i + 1];

      zoneHeight = SUB_INT32( blues->zone[blues->count].csTopEdge,
                              blues->zone[blues->count].csBottomEdge );

      if ( zoneHeight < 0 )
      {
        FT_TRACE4(( "cf2_blues_init: ignoring negative zone height\n" ));
        continue;   /* reject this zone */
      }

      if ( zoneHeight > maxZoneHeight )
      {
        /* take maximum before darkening adjustment      */
        /* so overshoot suppression point doesn't change */
        maxZoneHeight = zoneHeight;
      }

      /* Note: bottom zones are not adjusted for darkening amount */

      /* all OtherBlues are bottom zone */
      blues->zone[blues->count].bottomZone =
        TRUE;
      blues->zone[blues->count].csFlatEdge =
        blues->zone[blues->count].csTopEdge;

      blues->count += 1;
    }

    /* Adjust for FamilyBlues */

    /* Search for the nearest flat edge in `FamilyBlues' or                */
    /* `FamilyOtherBlues'.  According to the Black Book, any matching edge */
    /* must be within one device pixel                                     */

    csUnitsPerPixel = FT_DivFix( cf2_intToFixed( 1 ), blues->scale );

    /* loop on all zones in this font */
    for ( i = 0; i < blues->count; i++ )
    {
      size_t     j;
      CF2_Fixed  minDiff;
      CF2_Fixed  flatFamilyEdge, diff;
      /* value for this font */
      CF2_Fixed  flatEdge = blues->zone[i].csFlatEdge;


      if ( blues->zone[i].bottomZone )
      {
        /* In a bottom zone, the top edge is the flat edge.             */
        /* Search `FamilyOtherBlues' for bottom zones; look for closest */
        /* Family edge that is within the one pixel threshold.          */

        minDiff = CF2_FIXED_MAX;

        for ( j = 0; j < numFamilyOtherBlues; j += 2 )
        {
          /* top edge */
          flatFamilyEdge = familyOtherBlues[j + 1];

          diff = cf2_fixedAbs( SUB_INT32( flatEdge, flatFamilyEdge ) );

          if ( diff < minDiff && diff < csUnitsPerPixel )
          {
            blues->zone[i].csFlatEdge = flatFamilyEdge;
            minDiff                   = diff;

            if ( diff == 0 )
              break;
          }
        }

        /* check the first member of FamilyBlues, which is a bottom zone */
        if ( numFamilyBlues >= 2 )
        {
          /* top edge */
          flatFamilyEdge = familyBlues[1];

          diff = cf2_fixedAbs( SUB_INT32( flatEdge, flatFamilyEdge ) );

          if ( diff < minDiff && diff < csUnitsPerPixel )
            blues->zone[i].csFlatEdge = flatFamilyEdge;
        }
      }
      else
      {
        /* In a top zone, the bottom edge is the flat edge.                */
        /* Search `FamilyBlues' for top zones; skip first zone, which is a */
        /* bottom zone; look for closest Family edge that is within the    */
        /* one pixel threshold                                             */

        minDiff = CF2_FIXED_MAX;

        for ( j = 2; j < numFamilyBlues; j += 2 )
        {
          /* bottom edge */
          flatFamilyEdge = familyBlues[j];

          /* adjust edges of top zone upward by twice darkening amount */
          flatFamilyEdge += 2 * font->darkenY;      /* bottom edge */

          diff = cf2_fixedAbs( SUB_INT32( flatEdge, flatFamilyEdge ) );

          if ( diff < minDiff && diff < csUnitsPerPixel )
          {
            blues->zone[i].csFlatEdge = flatFamilyEdge;
            minDiff                   = diff;

            if ( diff == 0 )
              break;
          }
        }
      }
    }

    /* TODO: enforce separation of zones, including BlueFuzz */

    /* Adjust BlueScale; similar to AdjustBlueScale() in coretype */
    /* `bcsetup.c'.                                               */

    if ( maxZoneHeight > 0 )
    {
      if ( blues->blueScale > FT_DivFix( cf2_intToFixed( 1 ),
                                         maxZoneHeight ) )
      {
        /* clamp at maximum scale */
        blues->blueScale = FT_DivFix( cf2_intToFixed( 1 ),
                                      maxZoneHeight );
      }

      /*
       * TODO: Revisit the bug fix for 613448.  The minimum scale
       *       requirement catches a number of library fonts.  For
       *       example, with default BlueScale (.039625) and 0.4 minimum,
       *       the test below catches any font with maxZoneHeight < 10.1.
       *       There are library fonts ranging from 2 to 10 that get
       *       caught, including e.g., Eurostile LT Std Medium with
       *       maxZoneHeight of 6.
       *
       */
#if 0
      if ( blueScale < .4 / maxZoneHeight )
      {
        tetraphilia_assert( 0 );
        /* clamp at minimum scale, per bug 0613448 fix */
        blueScale = .4 / maxZoneHeight;
      }
#endif

    }

    /*
     * Suppress overshoot and boost blue zones at small sizes.  Boost
     * amount varies linearly from 0.5 pixel near 0 to 0 pixel at
     * blueScale cutoff.
     * Note: This boost amount is different from the coretype heuristic.
     *
     */

    if ( blues->scale < blues->blueScale )
    {
      blues->suppressOvershoot = TRUE;

      /* Change rounding threshold for `dsFlatEdge'.                    */
      /* Note: constant changed from 0.5 to 0.6 to avoid a problem with */
      /*       10ppem Arial                                             */

      blues->boost = cf2_doubleToFixed( .6 ) -
                       FT_MulDiv( cf2_doubleToFixed ( .6 ),
                                  blues->scale,
                                  blues->blueScale );
      if ( blues->boost > 0x7FFF )
      {
        /* boost must remain less than 0.5, or baseline could go negative */
        blues->boost = 0x7FFF;
      }
    }

    /* boost and darkening have similar effects; don't do both */
    if ( font->stemDarkened )
      blues->boost = 0;

    /* set device space alignment for each zone;    */
    /* apply boost amount before rounding flat edge */

    for ( i = 0; i < blues->count; i++ )
    {
      if ( blues->zone[i].bottomZone )
        blues->zone[i].dsFlatEdge = cf2_fixedRound(
                                      FT_MulFix(
                                        blues->zone[i].csFlatEdge,
                                        blues->scale ) -
                                      blues->boost );
      else
        blues->zone[i].dsFlatEdge = cf2_fixedRound(
                                      FT_MulFix(
                                        blues->zone[i].csFlatEdge,
                                        blues->scale ) +
                                      blues->boost );
    }
  }


  /*
   * Check whether `stemHint' is captured by one of the blue zones.
   *
   * Zero, one or both edges may be valid; only valid edges can be
   * captured.  For compatibility with CoolType, search top and bottom
   * zones in the same pass (see `BlueLock').  If a hint is captured,
   * return true and position the edge(s) in one of 3 ways:
   *
   * 1) If `BlueScale' suppresses overshoot, position the captured edge
   *    at the flat edge of the zone.
   * 2) If overshoot is not suppressed and `BlueShift' requires
   *    overshoot, position the captured edge a minimum of 1 device pixel
   *    from the flat edge.
   * 3) If overshoot is not suppressed or required, position the captured
   *    edge at the nearest device pixel.
   *
   */
  FT_LOCAL_DEF( FT_Bool )
  cf2_blues_capture( const CF2_Blues  blues,
                     CF2_Hint         bottomHintEdge,
                     CF2_Hint         topHintEdge )
  {
    /* TODO: validate? */
    CF2_Fixed  csFuzz = blues->blueFuzz;

    /* new position of captured edge */
    CF2_Fixed  dsNew;

    /* amount that hint is moved when positioned */
    CF2_Fixed  dsMove = 0;

    FT_Bool   captured = FALSE;
    CF2_UInt  i;


    /* assert edge flags are consistent */
    FT_ASSERT( !cf2_hint_isTop( bottomHintEdge ) &&
               !cf2_hint_isBottom( topHintEdge ) );

    /* TODO: search once without blue fuzz for compatibility with coretype? */
    for ( i = 0; i < blues->count; i++ )
    {
      if ( blues->zone[i].bottomZone           &&
           cf2_hint_isBottom( bottomHintEdge ) )
      {
        if ( SUB_INT32( blues->zone[i].csBottomEdge, csFuzz ) <=
               bottomHintEdge->csCoord                           &&
             bottomHintEdge->csCoord <=
               ADD_INT32( blues->zone[i].csTopEdge, csFuzz )     )
        {
          /* bottom edge captured by bottom zone */

          if ( blues->suppressOvershoot )
            dsNew = blues->zone[i].dsFlatEdge;

          else if ( SUB_INT32( blues->zone[i].csTopEdge,
                               bottomHintEdge->csCoord ) >=
                      blues->blueShift )
          {
            /* guarantee minimum of 1 pixel overshoot */
            dsNew = FT_MIN(
                      cf2_fixedRound( bottomHintEdge->dsCoord ),
                      SUB_INT32( blues->zone[i].dsFlatEdge,
                                 cf2_intToFixed( 1 ) ) );
          }

          else
          {
            /* simply round captured edge */
            dsNew = cf2_fixedRound( bottomHintEdge->dsCoord );
          }

          dsMove   = SUB_INT32( dsNew, bottomHintEdge->dsCoord );
          captured = TRUE;

          break;
        }
      }

      if ( !blues->zone[i].bottomZone && cf2_hint_isTop( topHintEdge ) )
      {
        if ( SUB_INT32( blues->zone[i].csBottomEdge, csFuzz ) <=
               topHintEdge->csCoord                              &&
             topHintEdge->csCoord <=
               ADD_INT32( blues->zone[i].csTopEdge, csFuzz )     )
        {
          /* top edge captured by top zone */

          if ( blues->suppressOvershoot )
            dsNew = blues->zone[i].dsFlatEdge;

          else if ( SUB_INT32( topHintEdge->csCoord,
                               blues->zone[i].csBottomEdge ) >=
                      blues->blueShift )
          {
            /* guarantee minimum of 1 pixel overshoot */
            dsNew = FT_MAX(
                      cf2_fixedRound( topHintEdge->dsCoord ),
                      blues->zone[i].dsFlatEdge + cf2_intToFixed( 1 ) );
          }

          else
          {
            /* simply round captured edge */
            dsNew = cf2_fixedRound( topHintEdge->dsCoord );
          }

          dsMove   = SUB_INT32( dsNew, topHintEdge->dsCoord );
          captured = TRUE;

          break;
        }
      }
    }

    if ( captured )
    {
      /* move both edges and flag them `locked' */
      if ( cf2_hint_isValid( bottomHintEdge ) )
      {
        bottomHintEdge->dsCoord = ADD_INT32( bottomHintEdge->dsCoord,
                                             dsMove );
        cf2_hint_lock( bottomHintEdge );
      }

      if ( cf2_hint_isValid( topHintEdge ) )
      {
        topHintEdge->dsCoord = ADD_INT32( topHintEdge->dsCoord, dsMove );
        cf2_hint_lock( topHintEdge );
      }
    }

    return captured;
  }


/* END */

kc3-lang/freetype/src/psaux/psblues.c

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kc3-lang/freetype /src/psaux/psblues.c