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Fixed fixed-point math issues. fvar tables now work fine, which means Skia finally works!

This commit is contained in:
Pietro Gagliardi 2017-11-04 02:44:38 -04:00
parent ad34745327
commit 6869f28718
2 changed files with 29 additions and 20 deletions
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2
darwin/attrstr.m
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@ -55,7 +55,7 @@ void uninitUnderlineColors(void)
}
// unlike the other systems, Core Text rolls family, size, weight, italic, width, AND opentype features into the "font" attribute
// TODO opentype features and AAT fvar table info is lost, so a handful of fonts in the font panel ("Titling" variants of some fonts and Skia and possibly others but those are the examples I know about) cannot be represented by uiDrawFontDescriptor; what *can* we do about this since this info is NOT part of the font on other platforms?
// TODO opentype features are lost, so a handful of fonts in the font panel ("Titling" variants of some fonts and possibly others but those are the examples I know about) cannot be represented by uiDrawFontDescriptor; what *can* we do about this since this info is NOT part of the font on other platforms?
// TODO see if we could use NSAttributedString?
// TODO consider renaming this struct and the fep variable(s)
// TODO restructure all this so the important details at the top are below with the combined font attributes type?

47
darwin/fontvariation.m
View File

@ -32,9 +32,10 @@
#define fvarWeight 0x77676874
#define fvarWidth 0x77647468
typedef uint32_t fixed1616;
typedef uint16_t fixed214;
typedef int32_t fixed1616;
typedef int16_t fixed214;
// note that Microsoft's data type list implies that *all* fixed-point types have the same format; it only gives specific examples for the 2.14 format, which confused me because I thought 16.16 worked differently, but eh
static fixed1616 doubleToFixed1616(double d)
{
double ipart, fpart;
@ -42,7 +43,12 @@ static fixed1616 doubleToFixed1616(double d)
int16_t i16;
uint32_t ret;
fpart = fabs(modf(d, &ipart));
fpart = modf(d, &ipart);
// fpart must be unsigned; modf() gives us fpart with the same sign as f (so we have to adjust both ipart and fpart appropriately)
if (fpart < 0) {
ipart -= 1;
fpart = 1 + fpart;
}
fpart *= 65536;
flong = lround(fpart);
i16 = (int16_t) ipart;
@ -52,14 +58,16 @@ static fixed1616 doubleToFixed1616(double d)
return (fixed1616) ret;
}
static double fixed1616ToDouble(fixed1616 f)
// see also https://stackoverflow.com/questions/8506317/fixed-point-unsigned-division-in-c and freetype's FT_DivFix()
// TODO figure out the specifics of freetype's more complex implementation that shifts b and juggles signs
static fixed1616 fixed1616Divide(fixed1616 a, fixed1616 b)
{
int16_t base;
double frac;
uint32_t u;
int64_t a64;
base = (int16_t) ((f >> 16) & 0xFFFF);
frac = ((double) (f & 0xFFFF)) / 65536;
return ((double) base) + frac;
u = (uint32_t) a;
a64 = (int64_t) (((uint64_t) u) << 16);
return (fixed1616) (a64 / b);
}
static fixed214 fixed1616ToFixed214(fixed1616 f)
@ -67,7 +75,7 @@ static fixed214 fixed1616ToFixed214(fixed1616 f)
uint32_t t;
uint32_t topbit;
t = f + 0x00000002;
t = (uint32_t) (f + 0x00000002);
topbit = t & 0x80000000;
t >>= 2;
if (topbit != 0)
@ -77,10 +85,12 @@ static fixed214 fixed1616ToFixed214(fixed1616 f)
static double fixed214ToDouble(fixed214 f)
{
uint16_t u;
double base;
double frac;
switch ((f >> 14) & 0x3) {
u = (uint16_t) f;
switch ((u >> 14) & 0x3) {
case 0:
base = 0;
break;
@ -93,22 +103,20 @@ static double fixed214ToDouble(fixed214 f)
case 3:
base = -1;
}
frac = ((double) (f & 0x3FFF)) / 16384;
frac = ((double) (u & 0x3FFF)) / 16384;
return base + frac;
}
static fixed1616 fixed214ToFixed1616(fixed214 f)
{
int32_t t;
uint32_t x;
t = (int32_t) ((int16_t) f);
t <<= 2;
x = (uint32_t) t;
return (fixed1616) (x - 0x00000002);
return (fixed1616) (t - 0x00000002);
}
static const fixed1616 fixed1616Negative1 = 0xFFFF0000;
static const fixed1616 fixed1616Negative1 = (int32_t) ((uint32_t) 0xFFFF0000);
static const fixed1616 fixed1616Zero = 0x00000000;
static const fixed1616 fixed1616Positive1 = 0x00010000;
@ -119,9 +127,9 @@ static fixed1616 fixed1616Normalize(fixed1616 val, fixed1616 min, fixed1616 max,
if (val > max)
val = max;
if (val < def)
return -(def - val) / (def - min);
return fixed1616Divide(-(def - val), (def - min));
if (val > def)
return (val - def) / (max - def);
return fixed1616Divide((val - def), (max - def));
return fixed1616Zero;
}
@ -148,7 +156,8 @@ static fixed214 normalizedTo214(fixed1616 val, const fixed1616 *avarMappings, si
start = end - 2;
startFrom = avarMappings[start];
startTo = avarMappings[start + 1];
val = (val - startFrom) / (endFrom - startFrom);
val = fixed1616Divide((val - startFrom), (endFrom - startFrom));
// TODO find a font with an avar table and make sure this works, or if we need to use special code for this too
val *= (endTo - startTo);
val += startTo;
}