The Tor Browser / file comparison
comparison: gfx/skia/trunk/src/core/SkQuadClipper.cpp
gfx/skia/trunk/src/core/SkQuadClipper.cpp
- branch
- TOR_BUG_9701
- changeset 8
- 97036ab72558
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| -1:000000000000 | 0:434b9087d240 |
|---|---|
| 1 /* | |
| 2 * Copyright 2009 The Android Open Source Project | |
| 3 * | |
| 4 * Use of this source code is governed by a BSD-style license that can be | |
| 5 * found in the LICENSE file. | |
| 6 */ | |
| 7 | |
| 8 #include "SkQuadClipper.h" | |
| 9 #include "SkGeometry.h" | |
| 10 | |
| 11 SkQuadClipper::SkQuadClipper() { | |
| 12 fClip.setEmpty(); | |
| 13 } | |
| 14 | |
| 15 void SkQuadClipper::setClip(const SkIRect& clip) { | |
| 16 // conver to scalars, since that's where we'll see the points | |
| 17 fClip.set(clip); | |
| 18 } | |
| 19 | |
| 20 /////////////////////////////////////////////////////////////////////////////// | |
| 21 | |
| 22 static bool chopMonoQuadAt(SkScalar c0, SkScalar c1, SkScalar c2, | |
| 23 SkScalar target, SkScalar* t) { | |
| 24 /* Solve F(t) = y where F(t) := [0](1-t)^2 + 2[1]t(1-t) + [2]t^2 | |
| 25 * We solve for t, using quadratic equation, hence we have to rearrange | |
| 26 * our cooefficents to look like At^2 + Bt + C | |
| 27 */ | |
| 28 SkScalar A = c0 - c1 - c1 + c2; | |
| 29 SkScalar B = 2*(c1 - c0); | |
| 30 SkScalar C = c0 - target; | |
| 31 | |
| 32 SkScalar roots[2]; // we only expect one, but make room for 2 for safety | |
| 33 int count = SkFindUnitQuadRoots(A, B, C, roots); | |
| 34 if (count) { | |
| 35 *t = roots[0]; | |
| 36 return true; | |
| 37 } | |
| 38 return false; | |
| 39 } | |
| 40 | |
| 41 static bool chopMonoQuadAtY(SkPoint pts[3], SkScalar y, SkScalar* t) { | |
| 42 return chopMonoQuadAt(pts[0].fY, pts[1].fY, pts[2].fY, y, t); | |
| 43 } | |
| 44 | |
| 45 /////////////////////////////////////////////////////////////////////////////// | |
| 46 | |
| 47 /* If we somehow returned the fact that we had to flip the pts in Y, we could | |
| 48 communicate that to setQuadratic, and then avoid having to flip it back | |
| 49 here (only to have setQuadratic do the flip again) | |
| 50 */ | |
| 51 bool SkQuadClipper::clipQuad(const SkPoint srcPts[3], SkPoint dst[3]) { | |
| 52 bool reverse; | |
| 53 | |
| 54 // we need the data to be monotonically increasing in Y | |
| 55 if (srcPts[0].fY > srcPts[2].fY) { | |
| 56 dst[0] = srcPts[2]; | |
| 57 dst[1] = srcPts[1]; | |
| 58 dst[2] = srcPts[0]; | |
| 59 reverse = true; | |
| 60 } else { | |
| 61 memcpy(dst, srcPts, 3 * sizeof(SkPoint)); | |
| 62 reverse = false; | |
| 63 } | |
| 64 | |
| 65 // are we completely above or below | |
| 66 const SkScalar ctop = fClip.fTop; | |
| 67 const SkScalar cbot = fClip.fBottom; | |
| 68 if (dst[2].fY <= ctop || dst[0].fY >= cbot) { | |
| 69 return false; | |
| 70 } | |
| 71 | |
| 72 SkScalar t; | |
| 73 SkPoint tmp[5]; // for SkChopQuadAt | |
| 74 | |
| 75 // are we partially above | |
| 76 if (dst[0].fY < ctop) { | |
| 77 if (chopMonoQuadAtY(dst, ctop, &t)) { | |
| 78 // take the 2nd chopped quad | |
| 79 SkChopQuadAt(dst, tmp, t); | |
| 80 dst[0] = tmp[2]; | |
| 81 dst[1] = tmp[3]; | |
| 82 } else { | |
| 83 // if chopMonoQuadAtY failed, then we may have hit inexact numerics | |
| 84 // so we just clamp against the top | |
| 85 for (int i = 0; i < 3; i++) { | |
| 86 if (dst[i].fY < ctop) { | |
| 87 dst[i].fY = ctop; | |
| 88 } | |
| 89 } | |
| 90 } | |
| 91 } | |
| 92 | |
| 93 // are we partially below | |
| 94 if (dst[2].fY > cbot) { | |
| 95 if (chopMonoQuadAtY(dst, cbot, &t)) { | |
| 96 SkChopQuadAt(dst, tmp, t); | |
| 97 dst[1] = tmp[1]; | |
| 98 dst[2] = tmp[2]; | |
| 99 } else { | |
| 100 // if chopMonoQuadAtY failed, then we may have hit inexact numerics | |
| 101 // so we just clamp against the bottom | |
| 102 for (int i = 0; i < 3; i++) { | |
| 103 if (dst[i].fY > cbot) { | |
| 104 dst[i].fY = cbot; | |
| 105 } | |
| 106 } | |
| 107 } | |
| 108 } | |
| 109 | |
| 110 if (reverse) { | |
| 111 SkTSwap<SkPoint>(dst[0], dst[2]); | |
| 112 } | |
| 113 return true; | |
| 114 } |
