#### Other Tools

```/* -*- 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() : mStart(gfxPoint()), mEnd(gfxPoint()) {} ```
``` 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) * (mEnd.x - mStart.x) - ```
``` (aOther.mEnd.x - aOther.mStart.x) * (mEnd.y - mStart.y); ```
``` ```
``` // 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) * (mStart.y - aOther.mStart.y) - ```
``` (aOther.mEnd.y - aOther.mStart.y) * (mStart.x - aOther.mStart.x); ```
``` ```
``` gfxFloat bnumerator = (mEnd.x - mStart.x) * (mStart.y - aOther.mStart.y) - ```
``` (mEnd.y - mStart.y) * (mStart.x - aOther.mStart.x); ```
``` ```
``` 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 */ ```