127 lines
4.1 KiB
C++
127 lines
4.1 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=8 sts=2 et sw=2 tw=80: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#include "SVGArcConverter.h"
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using namespace mozilla::gfx;
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namespace mozilla {
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//-----------------------------------------------------------------------
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static double CalcVectorAngle(double ux, double uy, double vx, double vy) {
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double ta = atan2(uy, ux);
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double tb = atan2(vy, vx);
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if (tb >= ta) return tb - ta;
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return 2 * M_PI - (ta - tb);
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}
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SVGArcConverter::SVGArcConverter(const Point& from, const Point& to,
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const Point& radii, double angle,
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bool largeArcFlag, bool sweepFlag) {
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MOZ_ASSERT(radii.x != 0.0f && radii.y != 0.0f, "Bad radii");
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const double radPerDeg = M_PI / 180.0;
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mSegIndex = 0;
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if (from == to) {
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mNumSegs = 0;
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return;
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}
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// Convert to center parameterization as shown in
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// http://www.w3.org/TR/SVG/implnote.html
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mRx = fabs(radii.x);
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mRy = fabs(radii.y);
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mSinPhi = sin(angle * radPerDeg);
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mCosPhi = cos(angle * radPerDeg);
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double x1dash =
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mCosPhi * (from.x - to.x) / 2.0 + mSinPhi * (from.y - to.y) / 2.0;
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double y1dash =
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-mSinPhi * (from.x - to.x) / 2.0 + mCosPhi * (from.y - to.y) / 2.0;
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double root;
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double numerator = mRx * mRx * mRy * mRy - mRx * mRx * y1dash * y1dash -
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mRy * mRy * x1dash * x1dash;
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if (numerator < 0.0) {
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// If mRx , mRy and are such that there is no solution (basically,
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// the ellipse is not big enough to reach from 'from' to 'to'
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// then the ellipse is scaled up uniformly until there is
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// exactly one solution (until the ellipse is just big enough).
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// -> find factor s, such that numerator' with mRx'=s*mRx and
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// mRy'=s*mRy becomes 0 :
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double s = sqrt(1.0 - numerator / (mRx * mRx * mRy * mRy));
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mRx *= s;
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mRy *= s;
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root = 0.0;
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} else {
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root = (largeArcFlag == sweepFlag ? -1.0 : 1.0) *
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sqrt(numerator /
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(mRx * mRx * y1dash * y1dash + mRy * mRy * x1dash * x1dash));
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}
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double cxdash = root * mRx * y1dash / mRy;
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double cydash = -root * mRy * x1dash / mRx;
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mC.x = mCosPhi * cxdash - mSinPhi * cydash + (from.x + to.x) / 2.0;
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mC.y = mSinPhi * cxdash + mCosPhi * cydash + (from.y + to.y) / 2.0;
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mTheta = CalcVectorAngle(1.0, 0.0, (x1dash - cxdash) / mRx,
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(y1dash - cydash) / mRy);
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double dtheta =
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CalcVectorAngle((x1dash - cxdash) / mRx, (y1dash - cydash) / mRy,
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(-x1dash - cxdash) / mRx, (-y1dash - cydash) / mRy);
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if (!sweepFlag && dtheta > 0)
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dtheta -= 2.0 * M_PI;
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else if (sweepFlag && dtheta < 0)
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dtheta += 2.0 * M_PI;
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// Convert into cubic bezier segments <= 90deg
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mNumSegs = static_cast<int>(ceil(fabs(dtheta / (M_PI / 2.0))));
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mDelta = dtheta / mNumSegs;
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mT = 8.0 / 3.0 * sin(mDelta / 4.0) * sin(mDelta / 4.0) / sin(mDelta / 2.0);
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mFrom = from;
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}
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bool SVGArcConverter::GetNextSegment(Point* cp1, Point* cp2, Point* to) {
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if (mSegIndex == mNumSegs) {
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return false;
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}
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double cosTheta1 = cos(mTheta);
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double sinTheta1 = sin(mTheta);
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double theta2 = mTheta + mDelta;
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double cosTheta2 = cos(theta2);
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double sinTheta2 = sin(theta2);
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// a) calculate endpoint of the segment:
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to->x = mCosPhi * mRx * cosTheta2 - mSinPhi * mRy * sinTheta2 + mC.x;
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to->y = mSinPhi * mRx * cosTheta2 + mCosPhi * mRy * sinTheta2 + mC.y;
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// b) calculate gradients at start/end points of segment:
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cp1->x =
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mFrom.x + mT * (-mCosPhi * mRx * sinTheta1 - mSinPhi * mRy * cosTheta1);
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cp1->y =
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mFrom.y + mT * (-mSinPhi * mRx * sinTheta1 + mCosPhi * mRy * cosTheta1);
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cp2->x = to->x + mT * (mCosPhi * mRx * sinTheta2 + mSinPhi * mRy * cosTheta2);
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cp2->y = to->y + mT * (mSinPhi * mRx * sinTheta2 - mCosPhi * mRy * cosTheta2);
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// do next segment
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mTheta = theta2;
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mFrom = *to;
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++mSegIndex;
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return true;
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}
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} // namespace mozilla
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