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comparison: gfx/skia/trunk/src/gpu/FlingState.cpp
gfx/skia/trunk/src/gpu/FlingState.cpp
- branch
- TOR_BUG_3246
- changeset 7
- 129ffea94266
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| -1:000000000000 | 0:d1664547a428 |
|---|---|
| 1 | |
| 2 /* | |
| 3 * Copyright 2010 Google Inc. | |
| 4 * | |
| 5 * Use of this source code is governed by a BSD-style license that can be | |
| 6 * found in the LICENSE file. | |
| 7 */ | |
| 8 | |
| 9 | |
| 10 | |
| 11 #include "FlingState.h" | |
| 12 #include "SkMatrix.h" | |
| 13 #include "SkTime.h" | |
| 14 | |
| 15 #define DISCRETIZE_TRANSLATE_TO_AVOID_FLICKER true | |
| 16 | |
| 17 static const float MAX_FLING_SPEED = 1500; | |
| 18 | |
| 19 static float pin_max_fling(float speed) { | |
| 20 if (speed > MAX_FLING_SPEED) { | |
| 21 speed = MAX_FLING_SPEED; | |
| 22 } | |
| 23 return speed; | |
| 24 } | |
| 25 | |
| 26 static double getseconds() { | |
| 27 return SkTime::GetMSecs() * 0.001; | |
| 28 } | |
| 29 | |
| 30 // returns +1 or -1, depending on the sign of x | |
| 31 // returns +1 if x is zero | |
| 32 static SkScalar SkScalarSign(SkScalar x) { | |
| 33 SkScalar sign = SK_Scalar1; | |
| 34 if (x < 0) { | |
| 35 sign = -sign; | |
| 36 } | |
| 37 return sign; | |
| 38 } | |
| 39 | |
| 40 static void unit_axis_align(SkVector* unit) { | |
| 41 const SkScalar TOLERANCE = SkDoubleToScalar(0.15); | |
| 42 if (SkScalarAbs(unit->fX) < TOLERANCE) { | |
| 43 unit->fX = 0; | |
| 44 unit->fY = SkScalarSign(unit->fY); | |
| 45 } else if (SkScalarAbs(unit->fY) < TOLERANCE) { | |
| 46 unit->fX = SkScalarSign(unit->fX); | |
| 47 unit->fY = 0; | |
| 48 } | |
| 49 } | |
| 50 | |
| 51 void FlingState::reset(float sx, float sy) { | |
| 52 fActive = true; | |
| 53 fDirection.set(sx, sy); | |
| 54 fSpeed0 = SkPoint::Normalize(&fDirection); | |
| 55 fSpeed0 = pin_max_fling(fSpeed0); | |
| 56 fTime0 = getseconds(); | |
| 57 | |
| 58 unit_axis_align(&fDirection); | |
| 59 // printf("---- speed %g dir %g %g\n", fSpeed0, fDirection.fX, fDirection.fY); | |
| 60 } | |
| 61 | |
| 62 bool FlingState::evaluateMatrix(SkMatrix* matrix) { | |
| 63 if (!fActive) { | |
| 64 return false; | |
| 65 } | |
| 66 | |
| 67 const float t = getseconds() - fTime0; | |
| 68 const float MIN_SPEED = 2; | |
| 69 const float K0 = 5.0; | |
| 70 const float K1 = 0.02; | |
| 71 const float speed = fSpeed0 * (sk_float_exp(- K0 * t) - K1); | |
| 72 if (speed <= MIN_SPEED) { | |
| 73 fActive = false; | |
| 74 return false; | |
| 75 } | |
| 76 float dist = (fSpeed0 - speed) / K0; | |
| 77 | |
| 78 // printf("---- time %g speed %g dist %g\n", t, speed, dist); | |
| 79 float tx = fDirection.fX * dist; | |
| 80 float ty = fDirection.fY * dist; | |
| 81 if (DISCRETIZE_TRANSLATE_TO_AVOID_FLICKER) { | |
| 82 tx = sk_float_round2int(tx); | |
| 83 ty = sk_float_round2int(ty); | |
| 84 } | |
| 85 matrix->setTranslate(tx, ty); | |
| 86 // printf("---- evaluate (%g %g)\n", tx, ty); | |
| 87 | |
| 88 return true; | |
| 89 } | |
| 90 | |
| 91 //////////////////////////////////////// | |
| 92 | |
| 93 GrAnimateFloat::GrAnimateFloat() : fTime0(0) {} | |
| 94 | |
| 95 void GrAnimateFloat::start(float v0, float v1, float duration) { | |
| 96 fValue0 = v0; | |
| 97 fValue1 = v1; | |
| 98 fDuration = duration; | |
| 99 if (duration > 0) { | |
| 100 fTime0 = SkTime::GetMSecs(); | |
| 101 if (!fTime0) { | |
| 102 fTime0 = 1; // time0 is our sentinel | |
| 103 } | |
| 104 } else { | |
| 105 fTime0 = 0; | |
| 106 } | |
| 107 } | |
| 108 | |
| 109 float GrAnimateFloat::evaluate() { | |
| 110 if (!fTime0) { | |
| 111 return fValue1; | |
| 112 } | |
| 113 | |
| 114 double elapsed = (SkTime::GetMSecs() - fTime0) * 0.001; | |
| 115 if (elapsed >= fDuration) { | |
| 116 fTime0 = 0; | |
| 117 return fValue1; | |
| 118 } | |
| 119 | |
| 120 double t = elapsed / fDuration; | |
| 121 if (true) { | |
| 122 t = (3 - 2 * t) * t * t; | |
| 123 } | |
| 124 return fValue0 + t * (fValue1 - fValue0); | |
| 125 } |
