mirror of
https://github.com/mozilla/gecko-dev.git
synced 2024-12-01 00:32:11 +00:00
77 lines
2.6 KiB
C
77 lines
2.6 KiB
C
/* -*- 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 */
|