Correct SkFixedToDouble.

include/core/SkFixed.h

 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkFixed_DEFINED
 #define SkFixed_DEFINED
 
@@ skipping 10 matching lines @@
 #define SK_Fixed1           (1 << 16)
 #define SK_FixedHalf        (1 << 15)
 #define SK_FixedMax         (0x7FFFFFFF)
 #define SK_FixedMin         (-SK_FixedMax)
 #define SK_FixedNaN         ((int) 0x80000000)
 #define SK_FixedPI          (0x3243F)
 #define SK_FixedSqrt2       (92682)
 #define SK_FixedTanPIOver8  (0x6A0A)
 #define SK_FixedRoot2Over2  (0xB505)
 
-#define SkFixedToFloat(x)   ((x) * 1.5258789e-5f)
+#define SkFixedToFloat(x)   ((x) * 1.52587890625e-5f)

[bungeman-skia, 2015/04/16 20:41:31]

Note that this diff might not cause any change, since I think we got lucky here
and all (current) compilers round the resulting value nicely, mapping this to
the same bit pattern. However, if the compiler didn't round so nicely, the old
value may have been off by one ulp.

 #if 1
     #define SkFloatToFixed(x)   ((SkFixed)((x) * SK_Fixed1))
 #else
     // pins over/under flows to max/min int32 (slower than just a cast)
     static inline SkFixed SkFloatToFixed(float x) {
         int64_t n = x * SK_Fixed1;
         return (SkFixed)n;
     }
 #endif
 
 #ifdef SK_DEBUG
     static inline SkFixed SkFloatToFixed_Check(float x) {
         int64_t n64 = (int64_t)(x * SK_Fixed1);
         SkFixed n32 = (SkFixed)n64;
         SkASSERT(n64 == n32);
         return n32;
     }
 #else
     #define SkFloatToFixed_Check(x) SkFloatToFixed(x)
 #endif
 
-#define SkFixedToDouble(x)  ((x) * 1.5258789e-5)
+#define SkFixedToDouble(x)  ((x) * 1.52587890625e-5)

[bungeman-skia, 2015/04/16 20:41:31]

Note that no one is actually using this at the moment, but we should update this
while it's easy to do so (and I have a test that would like to use it).

 #define SkDoubleToFixed(x)  ((SkFixed)((x) * SK_Fixed1))
 
 /** Converts an integer to a SkFixed, asserting that the result does not overflow
     a 32 bit signed integer
 */
 #ifdef SK_DEBUG
     inline SkFixed SkIntToFixed(int n)
     {
         SkASSERT(n >= -32768 && n <= 32767);
         return n << 16;
@@ skipping 87 matching lines @@
 #define Sk48Dot16FloorToInt(x)    static_cast<int>((x) >> 16)
 
 static inline float Sk48Dot16ToScalar(Sk48Dot16 x) {
     return static_cast<float>(x * 1.5258789e-5);  // x * (1.0f / (1 << 16))
 }
 #define SkFloatTo48Dot16(x)       (static_cast<Sk48Dot16>((x) * (1 << 16)))
 
 #define SkScalarTo48Dot16(x)      SkFloatTo48Dot16(x)
 
 #endif