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+/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef GFX_LINESEGMENT_H
+#define GFX_LINESEGMENT_H
+
+#include "gfxTypes.h"
+#include "gfxPoint.h"
+
+struct gfxLineSegment {
+ gfxLineSegment() {}
+ gfxLineSegment(const gfxPoint& aStart, const gfxPoint& aEnd)
+ : mStart(aStart), mEnd(aEnd) {}
+
+ bool PointsOnSameSide(const gfxPoint& aOne, const gfxPoint& aTwo) {
+ // Solve the equation
+ // y - mStart.y - ((mEnd.y - mStart.y)/(mEnd.x - mStart.x))(x - mStart.x)
+ // for both points
+
+ gfxFloat deltaY = (mEnd.y - mStart.y);
+ gfxFloat deltaX = (mEnd.x - mStart.x);
+
+ gfxFloat one = deltaX * (aOne.y - mStart.y) - deltaY * (aOne.x - mStart.x);
+ gfxFloat two = deltaX * (aTwo.y - mStart.y) - deltaY * (aTwo.x - mStart.x);
+
+ // If both results have the same sign, then we're on the correct side of the
+ // line. 0 (on the line) is always considered in.
+
+ if ((one >= 0 && two >= 0) || (one <= 0 && two <= 0)) return true;
+ return false;
+ }
+
+ /**
+ * Determines if two line segments intersect, and returns the intersection
+ * point in aIntersection if they do.
+ *
+ * Coincident lines are considered not intersecting as they don't have an
+ * intersection point.
+ */
+ bool Intersects(const gfxLineSegment& aOther, gfxPoint& aIntersection) {
+ gfxFloat denominator =
+ (aOther.mEnd.y - aOther.mStart.y).value * (mEnd.x - mStart.x).value -
+ (aOther.mEnd.x - aOther.mStart.x).value * (mEnd.y - mStart.y).value;
+
+ // Parallel or coincident. We treat coincident as not intersecting since
+ // these lines are guaranteed to have corners that intersect instead.
+ if (!denominator) {
+ return false;
+ }
+
+ gfxFloat anumerator = (aOther.mEnd.x - aOther.mStart.x).value *
+ (mStart.y - aOther.mStart.y).value -
+ (aOther.mEnd.y - aOther.mStart.y).value *
+ (mStart.x - aOther.mStart.x).value;
+
+ gfxFloat bnumerator =
+ (mEnd.x - mStart.x).value * (mStart.y - aOther.mStart.y).value -
+ (mEnd.y - mStart.y).value * (mStart.x - aOther.mStart.x).value;
+
+ gfxFloat ua = anumerator / denominator;
+ gfxFloat ub = bnumerator / denominator;
+
+ if (ua <= 0.0 || ua >= 1.0 || ub <= 0.0 || ub >= 1.0) {
+ // Intersection is outside of the segment
+ return false;
+ }
+
+ aIntersection = mStart + (mEnd - mStart) * ua;
+ return true;
+ }
+
+ gfxPoint mStart;
+ gfxPoint mEnd;
+};
+
+#endif /* GFX_LINESEGMENT_H */