1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/gfx/thebes/gfxLineSegment.h Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,77 @@
1.4 +/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 4 -*-
1.5 + * This Source Code Form is subject to the terms of the Mozilla Public
1.6 + * License, v. 2.0. If a copy of the MPL was not distributed with this
1.7 + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
1.8 +
1.9 +#ifndef GFX_LINESEGMENT_H
1.10 +#define GFX_LINESEGMENT_H
1.11 +
1.12 +#include "gfxTypes.h"
1.13 +#include "gfxPoint.h"
1.14 +
1.15 +struct gfxLineSegment {
1.16 + gfxLineSegment(const gfxPoint &aStart, const gfxPoint &aEnd)
1.17 + : mStart(aStart)
1.18 + , mEnd(aEnd)
1.19 + {}
1.20 +
1.21 + bool PointsOnSameSide(const gfxPoint& aOne, const gfxPoint& aTwo)
1.22 + {
1.23 + // Solve the equation y - mStart.y - ((mEnd.y - mStart.y)/(mEnd.x - mStart.x))(x - mStart.x) for both points
1.24 +
1.25 + gfxFloat deltaY = (mEnd.y - mStart.y);
1.26 + gfxFloat deltaX = (mEnd.x - mStart.x);
1.27 +
1.28 + gfxFloat one = deltaX * (aOne.y - mStart.y) - deltaY * (aOne.x - mStart.x);
1.29 + gfxFloat two = deltaX * (aTwo.y - mStart.y) - deltaY * (aTwo.x - mStart.x);
1.30 +
1.31 + // If both results have the same sign, then we're on the correct side of the line.
1.32 + // 0 (on the line) is always considered in.
1.33 +
1.34 + if ((one >= 0 && two >= 0) || (one <= 0 && two <= 0))
1.35 + return true;
1.36 + return false;
1.37 + }
1.38 +
1.39 + /**
1.40 + * Determines if two line segments intersect, and returns the intersection
1.41 + * point in aIntersection if they do.
1.42 + *
1.43 + * Coincident lines are considered not intersecting as they don't have an
1.44 + * intersection point.
1.45 + */
1.46 + bool Intersects(const gfxLineSegment& aOther, gfxPoint& aIntersection)
1.47 + {
1.48 + gfxFloat denominator = (aOther.mEnd.y - aOther.mStart.y) * (mEnd.x - mStart.x ) -
1.49 + (aOther.mEnd.x - aOther.mStart.x ) * (mEnd.y - mStart.y);
1.50 +
1.51 + // Parallel or coincident. We treat coincident as not intersecting since
1.52 + // these lines are guaranteed to have corners that intersect instead.
1.53 + if (!denominator) {
1.54 + return false;
1.55 + }
1.56 +
1.57 + gfxFloat anumerator = (aOther.mEnd.x - aOther.mStart.x) * (mStart.y - aOther.mStart.y) -
1.58 + (aOther.mEnd.y - aOther.mStart.y) * (mStart.x - aOther.mStart.x);
1.59 +
1.60 + gfxFloat bnumerator = (mEnd.x - mStart.x) * (mStart.y - aOther.mStart.y) -
1.61 + (mEnd.y - mStart.y) * (mStart.x - aOther.mStart.x);
1.62 +
1.63 + gfxFloat ua = anumerator / denominator;
1.64 + gfxFloat ub = bnumerator / denominator;
1.65 +
1.66 + if (ua <= 0.0 || ua >= 1.0 ||
1.67 + ub <= 0.0 || ub >= 1.0) {
1.68 + //Intersection is outside of the segment
1.69 + return false;
1.70 + }
1.71 +
1.72 + aIntersection = mStart + (mEnd - mStart) * ua;
1.73 + return true;
1.74 + }
1.75 +
1.76 + gfxPoint mStart;
1.77 + gfxPoint mEnd;
1.78 +};
1.79 +
1.80 +#endif /* GFX_LINESEGMENT_H */
