| /* |
| * Copyright 2016 Google Inc. |
| * |
| * Use of this source code is governed by a BSD-style license that can be |
| * found in the LICENSE file. |
| */ |
| |
| #ifndef SkScaleToSides_DEFINED |
| #define SkScaleToSides_DEFINED |
| |
| #include "include/core/SkScalar.h" |
| #include "include/core/SkTypes.h" |
| |
| #include <cmath> |
| #include <utility> |
| |
| class SkScaleToSides { |
| public: |
| // This code assumes that a and b fit in a float, and therefore the resulting smaller value |
| // of a and b will fit in a float. The side of the rectangle may be larger than a float. |
| // Scale must be less than or equal to the ratio limit / (*a + *b). |
| // This code assumes that NaN and Inf are never passed in. |
| static void AdjustRadii(double limit, double scale, SkScalar* a, SkScalar* b) { |
| SkASSERTF(scale < 1.0 && scale > 0.0, "scale: %g", scale); |
| |
| *a = (float)((double)*a * scale); |
| *b = (float)((double)*b * scale); |
| |
| if (*a + *b > limit) { |
| float* minRadius = a; |
| float* maxRadius = b; |
| |
| // Force minRadius to be the smaller of the two. |
| if (*minRadius > *maxRadius) { |
| using std::swap; |
| swap(minRadius, maxRadius); |
| } |
| |
| // newMinRadius must be float in order to give the actual value of the radius. |
| // The newMinRadius will always be smaller than limit. The largest that minRadius can be |
| // is 1/2 the ratio of minRadius : (minRadius + maxRadius), therefore in the resulting |
| // division, minRadius can be no larger than 1/2 limit + ULP. The newMinRadius can be |
| // 1/2 a ULP off at this point. |
| float newMinRadius = *minRadius; |
| |
| // Because newMaxRadius is the result of a double to float conversion, it can be larger |
| // than limit, but only by one ULP. |
| float newMaxRadius = (float)(limit - newMinRadius); |
| |
| // The total sum of newMinRadius and newMaxRadius can be upto 1.5 ULPs off. If the |
| // sum is greater than the limit then newMaxRadius may have to be reduced twice. |
| // Note: nextafterf is a c99 call and should be std::nextafter, but this is not |
| // implemented in the GCC ARM compiler. |
| if (newMaxRadius + newMinRadius > limit) { |
| newMaxRadius = nextafterf(newMaxRadius, 0.0f); |
| if (newMaxRadius + newMinRadius > limit) { |
| newMaxRadius = nextafterf(newMaxRadius, 0.0f); |
| } |
| } |
| *maxRadius = newMaxRadius; |
| } |
| |
| SkASSERTF(*a >= 0.0f && *b >= 0.0f, "a: %g, b: %g, limit: %g, scale: %g", *a, *b, limit, |
| scale); |
| |
| SkASSERTF(*a + *b <= limit, |
| "\nlimit: %.17f, sum: %.17f, a: %.10f, b: %.10f, scale: %.20f", |
| limit, *a + *b, *a, *b, scale); |
| } |
| }; |
| #endif // ScaleToSides_DEFINED |