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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 <cmath>
#include "SkScalar.h"
#include "SkTypes.h"
class ScaleToSides {
public:
// This code assumes that a and b fit in 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);
// This check is conservative. (double)*a + (double)*b >= (double)(*a + *b)
if ((double)*a + (double)*b > limit) {
float* minRadius = a;
float* maxRadius = b;
// Force minRadius to be the smaller of the two.
if (*minRadius > *maxRadius) {
SkTSwap(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.
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);
// If newMaxRadius forces the total over the limit, then it needs to be
// reduced by one ULP to be less than limit - newMinRadius.
// Note: nexttowardf is a c99 call and should be std::nexttoward, but this is not
// implemented in the ARM compiler.
if ((double)newMaxRadius + (double)newMinRadius > limit) {
newMaxRadius = nexttowardf(newMaxRadius, 0.0);
}
*maxRadius = newMaxRadius;
}
SkASSERTF(*a >= 0.0f && *b >= 0.0f, "a: %g, b: %g", *a, *b);
SkASSERTF((*a + *b) <= limit, "limit: %g, a: %g, b: %g", limit, *a, *b);
}
};
#endif // ScaleToSides_DEFINED
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