@ -85,45 +85,30 @@
/*************************************************************************/
/* */
/* Return the vertical metrics in font units for a given glyph. */
/* Greg Hitchcock from Microsoft told us that if there were no `vmtx' */
/* table, typoAscender/Descender from the `OS/2' table would be used */
/* instead, and if there were no `OS/2' table, use ascender/descender */
/* from the `hhea' table. But that is not what Microsoft's rasterizer */
/* apparently does: It uses the ppem value as the advance height, and */
/* sets the top side bearing to be zero. */
/* See macro `TT_LOADER_SET_PP' below for explanations. */
/* */
FT_LOCAL_DEF ( void )
TT_Get_VMetrics ( TT_Face face ,
FT_UInt idx ,
FT_Pos yMax ,
FT_Short * tsb ,
FT_UShort * ah )
{
if ( face - > vertical_info )
( ( SFNT_Service ) face - > sfnt ) - > get_metrics ( face , 1 , idx , tsb , ah ) ;
# if 1 /* Empirically determined, at variance with what MS said */
else
{
* tsb = 0 ;
* ah = face - > root . units_per_EM ;
}
# else /* This is what MS said to do. It isn't what they do, however. */
else if ( face - > os2 . version ! = 0xFFFFU )
{
* tsb = face - > os2 . sTypoAscender ;
* tsb = face - > os2 . sTypoAscender - yMax ;
* ah = face - > os2 . sTypoAscender - face - > os2 . sTypoDescender ;
}
else
{
* tsb = face - > horizontal . Ascender ;
* tsb = face - > horizontal . Ascender - yMax ;
* ah = face - > horizontal . Ascender - face - > horizontal . Descender ;
}
# endif
FT_TRACE5 ( ( " advance height (font units): %d \n " , * ah ) ) ;
FT_TRACE5 ( ( " top side bearing (font units): %d \n " , * tsb ) ) ;
}
@ -146,6 +131,7 @@
& left_bearing ,
& advance_width ) ;
TT_Get_VMetrics ( face , glyph_index ,
loader - > bbox . yMax ,
& top_bearing ,
& advance_height ) ;
@ -1263,18 +1249,78 @@
}
/* Calculate the four phantom points. */
/* The first two stand for horizontal origin and advance. */
/* The last two stand for vertical advance and origin. */
/*
* Calculate the phantom points
*
* Defining the right side bearing ( rsb ) as
*
* rsb = aw - ( lsb + xmax - xmin )
*
* ( with ` aw ' the advance width , ` lsb ' the left side bearing , and ` xmin '
* and ` xmax ' the glyph ' s minimum and maximum x value ) , the OpenType
* specification defines the initial position of horizontal phantom points
* as
*
* pp1 = ( xmin - lsb , 0 ) ,
* pp2 = ( pp1 + aw , 0 ) .
*
* However , the specification lacks the precise definition of vertical
* phantom points . Greg Hitchcock provided the following explanation .
*
* - a ` vmtx ' table is present
*
* For any glyph , the minimum and maximum y values ( ` ymin ' and ` ymax ' )
* are given in the ` glyf ' table , the top side bearing ( tsb ) and advance
* height ( ah ) are given in the ` vmtx ' table . The bottom side bearing
* ( bsb ) is then calculated as
*
* bsb = ah - ( tsb + ymax - ymin ) ,
*
* and the initial position of vertical phantom points is
*
* pp3 = ( x , ymax + tsb ) ,
* pp4 = ( x , pp3 - ah ) .
*
* See below for value ` x ' .
*
* - no ` vmtx ' table in the font
*
* If there is an ` OS / 2 ' table , we set
*
* DefaultAscender = sTypoAscender ,
* DefaultDescender = sTypoDescender ,
*
* otherwise we use data from the ` hhea ' table :
*
* DefaultAscender = Ascender ,
* DefaultDescender = Descender .
*
* With these two variables we can now set
*
* ah = DefaultAscender - sDefaultDescender ,
* tsb = DefaultAscender - yMax ,
*
* and proceed as if a ` vmtx ' table was present .
*
* Usually we have
*
* x = aw / 2 ,
*
* but there is a compatibility case where it can be set to
*
* x = - DefaultDescender -
* ( ( DefaultAscender - DefaultDescender - aw ) / 2 ) .
*
*/
# define TT_LOADER_SET_PP( loader ) \
do { \
( loader ) - > pp1 . x = ( loader ) - > bbox . xMin - ( loader ) - > left_bearing ; \
( loader ) - > pp1 . y = 0 ; \
( loader ) - > pp2 . x = ( loader ) - > pp1 . x + ( loader ) - > advance ; \
( loader ) - > pp2 . y = 0 ; \
( loader ) - > pp3 . x = 0 ; \
( loader ) - > pp3 . y = ( loader ) - > top_bearing + ( loader ) - > bbox . yMax ; \
( loader ) - > pp4 . x = 0 ; \
( loader ) - > pp3 . x = ( loader ) - > advance / 2 ;
( loader ) - > pp3 . y = ( loader ) - > bbox . yMax + ( loader ) - > top_bearing ; \
( loader ) - > pp4 . x = ( loader ) - > advance / 2 ;
( loader ) - > pp4 . y = ( loader ) - > pp3 . y - ( loader ) - > vadvance ; \
} while ( 0 )
Werner Lemberg
11 years ago