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comparison: gfx/thebes/gfxLineSegment.h
gfx/thebes/gfxLineSegment.h
- branch
- TOR_BUG_9701
- changeset 15
- b8a032363ba2
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| -1:000000000000 | 0:46785312d9df |
|---|---|
| 1 /* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 4 -*- | |
| 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/. */ | |
| 5 | |
| 6 #ifndef GFX_LINESEGMENT_H | |
| 7 #define GFX_LINESEGMENT_H | |
| 8 | |
| 9 #include "gfxTypes.h" | |
| 10 #include "gfxPoint.h" | |
| 11 | |
| 12 struct gfxLineSegment { | |
| 13 gfxLineSegment(const gfxPoint &aStart, const gfxPoint &aEnd) | |
| 14 : mStart(aStart) | |
| 15 , mEnd(aEnd) | |
| 16 {} | |
| 17 | |
| 18 bool PointsOnSameSide(const gfxPoint& aOne, const gfxPoint& aTwo) | |
| 19 { | |
| 20 // Solve the equation y - mStart.y - ((mEnd.y - mStart.y)/(mEnd.x - mStart.x))(x - mStart.x) for both points | |
| 21 | |
| 22 gfxFloat deltaY = (mEnd.y - mStart.y); | |
| 23 gfxFloat deltaX = (mEnd.x - mStart.x); | |
| 24 | |
| 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); | |
| 27 | |
| 28 // If both results have the same sign, then we're on the correct side of the line. | |
| 29 // 0 (on the line) is always considered in. | |
| 30 | |
| 31 if ((one >= 0 && two >= 0) || (one <= 0 && two <= 0)) | |
| 32 return true; | |
| 33 return false; | |
| 34 } | |
| 35 | |
| 36 /** | |
| 37 * Determines if two line segments intersect, and returns the intersection | |
| 38 * point in aIntersection if they do. | |
| 39 * | |
| 40 * Coincident lines are considered not intersecting as they don't have an | |
| 41 * intersection point. | |
| 42 */ | |
| 43 bool Intersects(const gfxLineSegment& aOther, gfxPoint& aIntersection) | |
| 44 { | |
| 45 gfxFloat denominator = (aOther.mEnd.y - aOther.mStart.y) * (mEnd.x - mStart.x ) - | |
| 46 (aOther.mEnd.x - aOther.mStart.x ) * (mEnd.y - mStart.y); | |
| 47 | |
| 48 // Parallel or coincident. We treat coincident as not intersecting since | |
| 49 // these lines are guaranteed to have corners that intersect instead. | |
| 50 if (!denominator) { | |
| 51 return false; | |
| 52 } | |
| 53 | |
| 54 gfxFloat anumerator = (aOther.mEnd.x - aOther.mStart.x) * (mStart.y - aOther.mStart.y) - | |
| 55 (aOther.mEnd.y - aOther.mStart.y) * (mStart.x - aOther.mStart.x); | |
| 56 | |
| 57 gfxFloat bnumerator = (mEnd.x - mStart.x) * (mStart.y - aOther.mStart.y) - | |
| 58 (mEnd.y - mStart.y) * (mStart.x - aOther.mStart.x); | |
| 59 | |
| 60 gfxFloat ua = anumerator / denominator; | |
| 61 gfxFloat ub = bnumerator / denominator; | |
| 62 | |
| 63 if (ua <= 0.0 || ua >= 1.0 || | |
| 64 ub <= 0.0 || ub >= 1.0) { | |
| 65 //Intersection is outside of the segment | |
| 66 return false; | |
| 67 } | |
| 68 | |
| 69 aIntersection = mStart + (mEnd - mStart) * ua; | |
| 70 return true; | |
| 71 } | |
| 72 | |
| 73 gfxPoint mStart; | |
| 74 gfxPoint mEnd; | |
| 75 }; | |
| 76 | |
| 77 #endif /* GFX_LINESEGMENT_H */ |
