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      1 /*
      2  * Copyright 2011 Google Inc.
      3  *
      4  * Use of this source code is governed by a BSD-style license that can be
      5  * found in the LICENSE file.
      6  */
      7 
      8 #ifndef SkClampRange_DEFINED
      9 #define SkClampRange_DEFINED
     10 
     11 #include "SkFixed.h"
     12 #include "SkScalar.h"
     13 
     14 #define SkGradFixed               SkFixed3232
     15 
     16 // We want the largest 32.32 value representable as a float. (float)0x7FFFFFFF
     17 // becomes too big, due to limited mantissa on the float and its rounding rules, so
     18 // we have to manually compute the next smaller value (aka nextafter).
     19 
     20 // #define SkGradFixedMaxScalar nextafterf(SkFixed3232ToFloat(SkFixed3232Max), 0)
     21 // #define SkGradFixedMinScalar nextafterf(SkFixed3232ToFloat(SkFixed3232Min), 0)
     22 #define SkGradFixedMaxScalar      ( 2147483520.0f)
     23 #define SkGradFixedMinScalar      (-2147483520.0f)
     24 #define SkScalarPinToGradFixed(x) SkScalarToFixed3232(SkTPin(x,                   \
     25                                                              SkGradFixedMinScalar,\
     26                                                              SkGradFixedMaxScalar))
     27 #define SkFixedToGradFixed(x)     SkFixedToFixed3232(x)
     28 #define SkGradFixedToFixed(x)     (SkFixed)((x) >> 16)
     29 #define kFracMax_SkGradFixed      0xFFFFFFFFLL
     30 
     31 /**
     32  *  Iteration fixed fx by dx, clamping as you go to [0..kFracMax_SkGradFixed], this class
     33  *  computes the (up to) 3 spans there are:
     34  *
     35  *  range0: use constant value V0
     36  *  range1: iterate as usual fx += dx
     37  *  range2: use constant value V1
     38  */
     39 struct SkClampRange {
     40     int fCount0;    // count for fV0
     41     int fCount1;    // count for interpolating (fV0...fV1)
     42     int fCount2;    // count for fV1
     43     SkGradFixed fFx1;   // initial fx value for the fCount1 range.
     44                     // only valid if fCount1 > 0
     45     int fV0, fV1;
     46 
     47     void init(SkGradFixed fx, SkGradFixed dx, int count, int v0, int v1);
     48 
     49     void validate(int count) const {
     50 #ifdef SK_DEBUG
     51         SkASSERT(fCount0 >= 0);
     52         SkASSERT(fCount1 >= 0);
     53         SkASSERT(fCount2 >= 0);
     54         SkASSERT(fCount0 + fCount1 + fCount2 == count);
     55 #endif
     56     }
     57 
     58 private:
     59     void initFor1(SkGradFixed fx);
     60 };
     61 
     62 #endif
     63