no bug - Bumping Firefox l10n changesets r=release a=l10n-bump DONTBUILD CLOSED TREE
[gecko.git] / gfx / thebes / gfxLineSegment.h
blob7f4ad13f61c81e4f221cde2f639e987981dfd892
1 /* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 2 -*-
2 * This Source Code Form is subject to the terms of the Mozilla Public
3 * License, v. 2.0. If a copy of the MPL was not distributed with this
4 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
6 #ifndef GFX_LINESEGMENT_H
7 #define GFX_LINESEGMENT_H
9 #include "gfxTypes.h"
10 #include "gfxPoint.h"
12 struct gfxLineSegment {
13 gfxLineSegment() {}
14 gfxLineSegment(const gfxPoint& aStart, const gfxPoint& aEnd)
15 : mStart(aStart), mEnd(aEnd) {}
17 bool PointsOnSameSide(const gfxPoint& aOne, const gfxPoint& aTwo) {
18 // Solve the equation
19 // y - mStart.y - ((mEnd.y - mStart.y)/(mEnd.x - mStart.x))(x - mStart.x)
20 // for both points
22 gfxFloat deltaY = (mEnd.y - mStart.y);
23 gfxFloat deltaX = (mEnd.x - mStart.x);
25 gfxFloat one = deltaX * (aOne.y - mStart.y) - deltaY * (aOne.x - mStart.x);
26 gfxFloat two = deltaX * (aTwo.y - mStart.y) - deltaY * (aTwo.x - mStart.x);
28 // If both results have the same sign, then we're on the correct side of the
29 // line. 0 (on the line) is always considered in.
31 if ((one >= 0 && two >= 0) || (one <= 0 && two <= 0)) return true;
32 return false;
35 /**
36 * Determines if two line segments intersect, and returns the intersection
37 * point in aIntersection if they do.
39 * Coincident lines are considered not intersecting as they don't have an
40 * intersection point.
42 bool Intersects(const gfxLineSegment& aOther, gfxPoint& aIntersection) {
43 gfxFloat denominator =
44 (aOther.mEnd.y - aOther.mStart.y).value * (mEnd.x - mStart.x).value -
45 (aOther.mEnd.x - aOther.mStart.x).value * (mEnd.y - mStart.y).value;
47 // Parallel or coincident. We treat coincident as not intersecting since
48 // these lines are guaranteed to have corners that intersect instead.
49 if (!denominator) {
50 return false;
53 gfxFloat anumerator = (aOther.mEnd.x - aOther.mStart.x).value *
54 (mStart.y - aOther.mStart.y).value -
55 (aOther.mEnd.y - aOther.mStart.y).value *
56 (mStart.x - aOther.mStart.x).value;
58 gfxFloat bnumerator =
59 (mEnd.x - mStart.x).value * (mStart.y - aOther.mStart.y).value -
60 (mEnd.y - mStart.y).value * (mStart.x - aOther.mStart.x).value;
62 gfxFloat ua = anumerator / denominator;
63 gfxFloat ub = bnumerator / denominator;
65 if (ua <= 0.0 || ua >= 1.0 || ub <= 0.0 || ub >= 1.0) {
66 // Intersection is outside of the segment
67 return false;
70 aIntersection = mStart + (mEnd - mStart) * ua;
71 return true;
74 gfxPoint mStart;
75 gfxPoint mEnd;
78 #endif /* GFX_LINESEGMENT_H */