gecko-dev/gfx/2d/PathHelpers.h

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