mirror of https://github.com/axmolengine/axmol.git
213 lines
9.0 KiB
C
213 lines
9.0 KiB
C
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/* libs/graphics/sgl/SkGeometry.h
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**
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** Copyright 2006, The Android Open Source Project
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**
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** Licensed under the Apache License, Version 2.0 (the "License");
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** you may not use this file except in compliance with the License.
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** You may obtain a copy of the License at
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**
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** http://www.apache.org/licenses/LICENSE-2.0
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**
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** Unless required by applicable law or agreed to in writing, software
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** distributed under the License is distributed on an "AS IS" BASIS,
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** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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** See the License for the specific language governing permissions and
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** limitations under the License.
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*/
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#ifndef SkGeometry_DEFINED
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#define SkGeometry_DEFINED
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#include "SkMatrix.h"
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/** An XRay is a half-line that runs from the specific point/origin to
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+infinity in the X direction. e.g. XRay(3,5) is the half-line
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(3,5)....(infinity, 5)
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*/
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typedef SkPoint SkXRay;
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/** Given a line segment from pts[0] to pts[1], and an xray, return true if
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they intersect. Optional outgoing "ambiguous" argument indicates
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whether the answer is ambiguous because the query occurred exactly at
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one of the endpoints' y coordinates, indicating that another query y
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coordinate is preferred for robustness.
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*/
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bool SkXRayCrossesLine(const SkXRay& pt, const SkPoint pts[2],
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bool* ambiguous = NULL);
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/** Given a quadratic equation Ax^2 + Bx + C = 0, return 0, 1, 2 roots for the
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equation.
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*/
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int SkFindUnitQuadRoots(SkScalar A, SkScalar B, SkScalar C, SkScalar roots[2]);
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///////////////////////////////////////////////////////////////////////////////
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/** Set pt to the point on the src quadratic specified by t. t must be
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0 <= t <= 1.0
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*/
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void SkEvalQuadAt(const SkPoint src[3], SkScalar t, SkPoint* pt,
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SkVector* tangent = NULL);
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void SkEvalQuadAtHalf(const SkPoint src[3], SkPoint* pt,
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SkVector* tangent = NULL);
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/** Given a src quadratic bezier, chop it at the specified t value,
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where 0 < t < 1, and return the two new quadratics in dst:
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dst[0..2] and dst[2..4]
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*/
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void SkChopQuadAt(const SkPoint src[3], SkPoint dst[5], SkScalar t);
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/** Given a src quadratic bezier, chop it at the specified t == 1/2,
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The new quads are returned in dst[0..2] and dst[2..4]
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*/
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void SkChopQuadAtHalf(const SkPoint src[3], SkPoint dst[5]);
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/** Given the 3 coefficients for a quadratic bezier (either X or Y values), look
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for extrema, and return the number of t-values that are found that represent
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these extrema. If the quadratic has no extrema betwee (0..1) exclusive, the
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function returns 0.
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Returned count tValues[]
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0 ignored
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1 0 < tValues[0] < 1
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*/
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int SkFindQuadExtrema(SkScalar a, SkScalar b, SkScalar c, SkScalar tValues[1]);
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/** Given 3 points on a quadratic bezier, chop it into 1, 2 beziers such that
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the resulting beziers are monotonic in Y. This is called by the scan converter.
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Depending on what is returned, dst[] is treated as follows
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0 dst[0..2] is the original quad
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1 dst[0..2] and dst[2..4] are the two new quads
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*/
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int SkChopQuadAtYExtrema(const SkPoint src[3], SkPoint dst[5]);
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int SkChopQuadAtXExtrema(const SkPoint src[3], SkPoint dst[5]);
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/** Given 3 points on a quadratic bezier, divide it into 2 quadratics
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if the point of maximum curvature exists on the quad segment.
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Depending on what is returned, dst[] is treated as follows
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1 dst[0..2] is the original quad
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2 dst[0..2] and dst[2..4] are the two new quads
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If dst == null, it is ignored and only the count is returned.
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*/
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int SkChopQuadAtMaxCurvature(const SkPoint src[3], SkPoint dst[5]);
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/** Given 3 points on a quadratic bezier, use degree elevation to
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convert it into the cubic fitting the same curve. The new cubic
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curve is returned in dst[0..3].
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*/
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SK_API void SkConvertQuadToCubic(const SkPoint src[3], SkPoint dst[4]);
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///////////////////////////////////////////////////////////////////////////////
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/** Convert from parametric from (pts) to polynomial coefficients
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coeff[0]*T^3 + coeff[1]*T^2 + coeff[2]*T + coeff[3]
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*/
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void SkGetCubicCoeff(const SkPoint pts[4], SkScalar cx[4], SkScalar cy[4]);
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/** Set pt to the point on the src cubic specified by t. t must be
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0 <= t <= 1.0
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*/
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void SkEvalCubicAt(const SkPoint src[4], SkScalar t, SkPoint* locOrNull,
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SkVector* tangentOrNull, SkVector* curvatureOrNull);
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/** Given a src cubic bezier, chop it at the specified t value,
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where 0 < t < 1, and return the two new cubics in dst:
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dst[0..3] and dst[3..6]
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*/
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void SkChopCubicAt(const SkPoint src[4], SkPoint dst[7], SkScalar t);
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void SkChopCubicAt(const SkPoint src[4], SkPoint dst[7], const SkScalar t[],
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int t_count);
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/** Given a src cubic bezier, chop it at the specified t == 1/2,
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The new cubics are returned in dst[0..3] and dst[3..6]
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*/
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void SkChopCubicAtHalf(const SkPoint src[4], SkPoint dst[7]);
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/** Given the 4 coefficients for a cubic bezier (either X or Y values), look
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for extrema, and return the number of t-values that are found that represent
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these extrema. If the cubic has no extrema betwee (0..1) exclusive, the
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function returns 0.
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Returned count tValues[]
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0 ignored
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1 0 < tValues[0] < 1
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2 0 < tValues[0] < tValues[1] < 1
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*/
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int SkFindCubicExtrema(SkScalar a, SkScalar b, SkScalar c, SkScalar d,
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SkScalar tValues[2]);
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/** Given 4 points on a cubic bezier, chop it into 1, 2, 3 beziers such that
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the resulting beziers are monotonic in Y. This is called by the scan converter.
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Depending on what is returned, dst[] is treated as follows
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0 dst[0..3] is the original cubic
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1 dst[0..3] and dst[3..6] are the two new cubics
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2 dst[0..3], dst[3..6], dst[6..9] are the three new cubics
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If dst == null, it is ignored and only the count is returned.
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*/
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int SkChopCubicAtYExtrema(const SkPoint src[4], SkPoint dst[10]);
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int SkChopCubicAtXExtrema(const SkPoint src[4], SkPoint dst[10]);
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/** Given a cubic bezier, return 0, 1, or 2 t-values that represent the
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inflection points.
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*/
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int SkFindCubicInflections(const SkPoint src[4], SkScalar tValues[2]);
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/** Return 1 for no chop, or 2 for having chopped the cubic at its
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inflection point.
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*/
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int SkChopCubicAtInflections(const SkPoint src[4], SkPoint dst[10]);
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int SkFindCubicMaxCurvature(const SkPoint src[4], SkScalar tValues[3]);
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int SkChopCubicAtMaxCurvature(const SkPoint src[4], SkPoint dst[13],
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SkScalar tValues[3] = NULL);
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/** Given a monotonic cubic bezier, determine whether an xray intersects the
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cubic.
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By definition the cubic is open at the starting point; in other
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words, if pt.fY is equivalent to cubic[0].fY, and pt.fX is to the
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left of the curve, the line is not considered to cross the curve,
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but if it is equal to cubic[3].fY then it is considered to
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cross.
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Optional outgoing "ambiguous" argument indicates whether the answer is
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ambiguous because the query occurred exactly at one of the endpoints' y
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coordinates, indicating that another query y coordinate is preferred
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for robustness.
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*/
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bool SkXRayCrossesMonotonicCubic(const SkXRay& pt, const SkPoint cubic[4],
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bool* ambiguous = NULL);
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/** Given an arbitrary cubic bezier, return the number of times an xray crosses
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the cubic. Valid return values are [0..3]
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By definition the cubic is open at the starting point; in other
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words, if pt.fY is equivalent to cubic[0].fY, and pt.fX is to the
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left of the curve, the line is not considered to cross the curve,
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but if it is equal to cubic[3].fY then it is considered to
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cross.
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Optional outgoing "ambiguous" argument indicates whether the answer is
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ambiguous because the query occurred exactly at one of the endpoints' y
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coordinates or at a tangent point, indicating that another query y
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coordinate is preferred for robustness.
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*/
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int SkNumXRayCrossingsForCubic(const SkXRay& pt, const SkPoint cubic[4],
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bool* ambiguous = NULL);
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///////////////////////////////////////////////////////////////////////////////
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enum SkRotationDirection {
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kCW_SkRotationDirection,
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kCCW_SkRotationDirection
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};
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/** Maximum number of points needed in the quadPoints[] parameter for
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SkBuildQuadArc()
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*/
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#define kSkBuildQuadArcStorage 17
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/** Given 2 unit vectors and a rotation direction, fill out the specified
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array of points with quadratic segments. Return is the number of points
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written to, which will be { 0, 3, 5, 7, ... kSkBuildQuadArcStorage }
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matrix, if not null, is appled to the points before they are returned.
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*/
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int SkBuildQuadArc(const SkVector& unitStart, const SkVector& unitStop,
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SkRotationDirection, const SkMatrix*, SkPoint quadPoints[]);
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#endif
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