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- /*
- * 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
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