mirror of
https://github.com/mozilla/gecko-dev.git
synced 2024-11-06 00:55:37 +00:00
78 lines
2.5 KiB
C
78 lines
2.5 KiB
C
/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 4 -*-
|
|
* 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(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 */
|