1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/gfx/skia/trunk/src/core/SkBitmapProcState_utils.h Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,40 @@
1.4 +#ifndef SkBitmapProcState_utils_DEFINED
1.5 +#define SkBitmapProcState_utils_DEFINED
1.6 +
1.7 +// Helper to ensure that when we shift down, we do it w/o sign-extension
1.8 +// so the caller doesn't have to manually mask off the top 16 bits
1.9 +//
1.10 +static unsigned SK_USHIFT16(unsigned x) {
1.11 + return x >> 16;
1.12 +}
1.13 +
1.14 +/*
1.15 + * The decal_ functions require that
1.16 + * 1. dx > 0
1.17 + * 2. [fx, fx+dx, fx+2dx, fx+3dx, ... fx+(count-1)dx] are all <= maxX
1.18 + *
1.19 + * In addition, we use SkFractionalInt to keep more fractional precision than
1.20 + * just SkFixed, so we will abort the decal_ call if dx is very small, since
1.21 + * the decal_ function just operates on SkFixed. If that were changed, we could
1.22 + * skip the very_small test here.
1.23 + */
1.24 +static inline bool can_truncate_to_fixed_for_decal(SkFractionalInt frX,
1.25 + SkFractionalInt frDx,
1.26 + int count, unsigned max) {
1.27 + SkFixed dx = SkFractionalIntToFixed(frDx);
1.28 +
1.29 + // if decal_ kept SkFractionalInt precision, this would just be dx <= 0
1.30 + // I just made up the 1/256. Just don't want to perceive accumulated error
1.31 + // if we truncate frDx and lose its low bits.
1.32 + if (dx <= SK_Fixed1 / 256) {
1.33 + return false;
1.34 + }
1.35 +
1.36 + // We cast to unsigned so we don't have to check for negative values, which
1.37 + // will now appear as very large positive values, and thus fail our test!
1.38 + SkFixed fx = SkFractionalIntToFixed(frX);
1.39 + return (unsigned)SkFixedFloorToInt(fx) <= max &&
1.40 + (unsigned)SkFixedFloorToInt(fx + dx * (count - 1)) < max;
1.41 +}
1.42 +
1.43 +#endif /* #ifndef SkBitmapProcState_utils_DEFINED */
