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123 lines
4.7 KiB
C++
123 lines
4.7 KiB
C++
/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 2 -*-
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* ***** BEGIN LICENSE BLOCK *****
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* Version: MPL 1.1/GPL 2.0/LGPL 2.1
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*
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* The contents of this file are subject to the Mozilla Public License Version
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* 1.1 (the "License"); you may not use this file except in compliance with
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* the License. You may obtain a copy of the License at
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* http://www.mozilla.org/MPL/
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*
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* Software distributed under the License is distributed on an "AS IS" basis,
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* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
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* for the specific language governing rights and limitations under the
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* License.
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*
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* The Original Code is Mozilla Corporation code.
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*
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* The Initial Developer of the Original Code is Mozilla Foundation.
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* Portions created by the Initial Developer are Copyright (C) 2011
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* the Initial Developer. All Rights Reserved.
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*
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* Contributor(s):
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* Matt Woodrow <mwoodrow@mozilla.com>
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*
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* Alternatively, the contents of this file may be used under the terms of
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* either the GNU General Public License Version 2 or later (the "GPL"), or
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* the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
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* in which case the provisions of the GPL or the LGPL are applicable instead
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* of those above. If you wish to allow use of your version of this file only
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* under the terms of either the GPL or the LGPL, and not to allow others to
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* use your version of this file under the terms of the MPL, indicate your
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* decision by deleting the provisions above and replace them with the notice
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* and other provisions required by the GPL or the LGPL. If you do not delete
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* the provisions above, a recipient may use your version of this file under
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* the terms of any one of the MPL, the GPL or the LGPL.
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*
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* ***** END LICENSE BLOCK ***** */
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#ifndef MOZILLA_GFX_PATHHELPERS_H_
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#define MOZILLA_GFX_PATHHELPERS_H_
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#include "2D.h"
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#ifndef M_PI
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#define M_PI 3.14159265358979323846
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#endif
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namespace mozilla {
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namespace gfx {
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template <typename T>
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void ArcToBezier(T* aSink, const Point &aOrigin, float aRadius, float aStartAngle,
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float aEndAngle, bool aAntiClockwise)
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{
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Point startPoint(aOrigin.x + cos(aStartAngle) * aRadius,
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aOrigin.y + sin(aStartAngle) * aRadius);
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aSink->LineTo(startPoint);
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// Clockwise we always sweep from the smaller to the larger angle, ccw
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// it's vice versa.
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if (!aAntiClockwise && (aEndAngle < aStartAngle)) {
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Float correction = ceil((aStartAngle - aEndAngle) / (2.0f * M_PI));
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aEndAngle += correction * 2.0f * M_PI;
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} else if (aAntiClockwise && (aStartAngle < aEndAngle)) {
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Float correction = ceil((aEndAngle - aStartAngle) / (2.0f * M_PI));
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aStartAngle += correction * 2.0f * M_PI;
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}
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// Sweeping more than 2 * pi is a full circle.
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if (!aAntiClockwise && (aEndAngle - aStartAngle > 2 * M_PI)) {
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aEndAngle = aStartAngle + 2.0f * M_PI;
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} else if (aAntiClockwise && (aStartAngle - aEndAngle > 2.0f * M_PI)) {
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aEndAngle = aStartAngle - 2.0f * M_PI;
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}
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// Calculate the total arc we're going to sweep.
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Float arcSweepLeft = fabs(aEndAngle - aStartAngle);
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Float sweepDirection = aAntiClockwise ? -1.0f : 1.0f;
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Float currentStartAngle = aStartAngle;
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while (arcSweepLeft > 0) {
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// We guarantee here the current point is the start point of the next
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// curve segment.
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Float currentEndAngle;
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if (arcSweepLeft > M_PI / 2.0f) {
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currentEndAngle = currentStartAngle + M_PI / 2.0f * sweepDirection;
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} else {
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currentEndAngle = currentStartAngle + arcSweepLeft * sweepDirection;
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}
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Point currentStartPoint(aOrigin.x + cos(currentStartAngle) * aRadius,
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aOrigin.y + sin(currentStartAngle) * aRadius);
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Point currentEndPoint(aOrigin.x + cos(currentEndAngle) * aRadius,
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aOrigin.y + sin(currentEndAngle) * aRadius);
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// Calculate kappa constant for partial curve. The sign of angle in the
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// tangent will actually ensure this is negative for a counter clockwise
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// sweep, so changing signs later isn't needed.
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Float kappa = (4.0f / 3.0f) * tan((currentEndAngle - currentStartAngle) / 4.0f) * aRadius;
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Point tangentStart(-sin(currentStartAngle), cos(currentStartAngle));
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Point cp1 = currentStartPoint;
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cp1 += tangentStart * kappa;
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Point revTangentEnd(sin(currentEndAngle), -cos(currentEndAngle));
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Point cp2 = currentEndPoint;
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cp2 += revTangentEnd * kappa;
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aSink->BezierTo(cp1, cp2, currentEndPoint);
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arcSweepLeft -= M_PI / 2.0f;
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currentStartAngle = currentEndAngle;
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}
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}
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}
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}
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#endif /* MOZILLA_GFX_PATHHELPERS_H_ */
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