1 /* 2 * Copyright 2016 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 SkScaleToSides_DEFINED 9 #define SkScaleToSides_DEFINED 10 11 #include "include/core/SkScalar.h" 12 #include "include/core/SkTypes.h" 13 14 #include <cmath> 15 #include <utility> 16 17 class SkScaleToSides { 18 public: 19 // This code assumes that a and b fit in a float, and therefore the resulting smaller value 20 // of a and b will fit in a float. The side of the rectangle may be larger than a float. 21 // Scale must be less than or equal to the ratio limit / (*a + *b). 22 // This code assumes that NaN and Inf are never passed in. AdjustRadii(double limit,double scale,SkScalar * a,SkScalar * b)23 static void AdjustRadii(double limit, double scale, SkScalar* a, SkScalar* b) { 24 SkASSERTF(scale < 1.0 && scale > 0.0, "scale: %g", scale); 25 26 *a = (float)((double)*a * scale); 27 *b = (float)((double)*b * scale); 28 29 if (*a + *b > limit) { 30 float* minRadius = a; 31 float* maxRadius = b; 32 33 // Force minRadius to be the smaller of the two. 34 if (*minRadius > *maxRadius) { 35 using std::swap; 36 swap(minRadius, maxRadius); 37 } 38 39 // newMinRadius must be float in order to give the actual value of the radius. 40 // The newMinRadius will always be smaller than limit. The largest that minRadius can be 41 // is 1/2 the ratio of minRadius : (minRadius + maxRadius), therefore in the resulting 42 // division, minRadius can be no larger than 1/2 limit + ULP. 43 float newMinRadius = *minRadius; 44 45 float newMaxRadius = (float)(limit - newMinRadius); 46 47 // Reduce newMaxRadius an ulp at a time until it fits. This usually never happens, 48 // but if it does it could be 1 or 2 times. In certain pathological cases it could be 49 // more. Max iterations seen so far is 17. 50 while (newMaxRadius + newMinRadius > limit) { 51 newMaxRadius = nextafterf(newMaxRadius, 0.0f); 52 } 53 *maxRadius = newMaxRadius; 54 } 55 56 SkASSERTF(*a >= 0.0f && *b >= 0.0f, "a: %g, b: %g, limit: %g, scale: %g", *a, *b, limit, 57 scale); 58 59 SkASSERTF(*a + *b <= limit, 60 "\nlimit: %.17f, sum: %.17f, a: %.10f, b: %.10f, scale: %.20f", 61 limit, *a + *b, *a, *b, scale); 62 } 63 }; 64 #endif // ScaleToSides_DEFINED 65