diff --git a/ChangeLog b/ChangeLog index 181ade9ae..cdbec0db1 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,11 @@ +2017-03-14 Werner Lemberg + + [sfnt] Implement PS names for font instances [2/3]. + + * src/sfnt/sfdriver.c (fix2float) [TT_CONFIG_OPTION_GX_VAR_SUPPORT]: + New function to find the shortest representation of a 16.16 + fractional number. + 2017-03-14 Werner Lemberg [sfnt] Implement PS names for font instances [1/3]. diff --git a/src/sfnt/sfdriver.c b/src/sfnt/sfdriver.c index 455c49061..f0ae98168 100644 --- a/src/sfnt/sfdriver.c +++ b/src/sfnt/sfdriver.c @@ -601,6 +601,126 @@ } +#ifdef TT_CONFIG_OPTION_GX_VAR_SUPPORT + + /* + * Find the shortest decimal representation of a 16.16 fixed point + * number. The function fills `buf' with the result, returning a pointer + * to the position after the representation's last byte. + */ + + static char* + fixed2float( FT_Int fixed, + char* buf ) + { + char* p; + char* q; + char tmp[5]; + + FT_Int int_part; + FT_Int frac_part; + + FT_Int i; + + + p = buf; + + if ( fixed == 0 ) + { + *p++ = '0'; + return p; + } + + if ( fixed < 0 ) + { + *p++ = '-'; + fixed = -fixed; + } + + int_part = ( fixed >> 16 ) & 0xFFFF; + frac_part = fixed & 0xFFFF; + + /* get digits of integer part (in reverse order) */ + q = tmp; + while ( int_part > 0 ) + { + *q++ = '0' + int_part % 10; + int_part /= 10; + } + + /* copy digits in correct order to buffer */ + while ( q > tmp ) + *p++ = *--q; + + if ( !frac_part ) + return p; + + /* save position of point */ + q = p; + *p++ = '.'; + + /* apply rounding */ + frac_part = frac_part * 10 + 5; + + /* get digits of fractional part */ + for ( i = 0; i < 5; i++ ) + { + *p++ = '0' + frac_part / 0x10000L; + + frac_part %= 0x10000L; + if ( !frac_part ) + break; + + frac_part *= 10; + } + + /* + If the remainder stored in `frac_part' (after the last FOR loop) is + smaller than 34480*10, the resulting decimal value minus 0.00001 is + an equivalent representation of `fixed'. + + The above FOR loop always finds the larger of the two values; I + verified this by iterating over all possible fixed point numbers. + + If the remainder is 17232*10, both values are equally good, and we + take the next even number (following IEEE 754's `round to nearest, + ties to even' rounding rule). + + If the remainder is smaller than 17232*10, the lower of the two + numbers is nearer to the exact result (values 17232 and 34480 were + also found by testing all possible fixed point values). + + We use this to find a shorter decimal representation. If not ending + with digit zero, we take the representation with less error. + */ + p--; + if ( p - q == 5 ) /* five digits? */ + { + /* take the representation that has zero as the last digit */ + if ( frac_part < 34480 * 10 && + *p == '1' ) + *p = '0'; + + /* otherwise use the one with less error */ + else if ( frac_part == 17232 * 10 && + *p & 1 ) + *p -= 1; + + else if ( frac_part < 17232 * 10 && + *p != '0' ) + *p -= 1; + } + + /* remove trailing zeros */ + while ( *p == '0' ) + *p-- = '\0'; + + return p + 1; + } + +#endif /* TT_CONFIG_OPTION_GX_VAR_SUPPORT */ + + static const char* sfnt_get_ps_name( TT_Face face ) {