1 /* 2 Copyright 2010 Google Inc. 3 4 Licensed under the Apache License, Version 2.0 (the "License"); 5 you may not use this file except in compliance with the License. 6 You may obtain a copy of the License at 7 8 http://www.apache.org/licenses/LICENSE-2.0 9 10 Unless required by applicable law or agreed to in writing, software 11 distributed under the License is distributed on an "AS IS" BASIS, 12 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 See the License for the specific language governing permissions and 14 limitations under the License. 15 */ 16 17 18 #include "FlingState.h" 19 #include "SkMatrix.h" 20 #include "SkTime.h" 21 22 #define DISCRETIZE_TRANSLATE_TO_AVOID_FLICKER true 23 24 static const float MAX_FLING_SPEED = 1500; 25 pin_max_fling(float speed)26 static float pin_max_fling(float speed) { 27 if (speed > MAX_FLING_SPEED) { 28 speed = MAX_FLING_SPEED; 29 } 30 return speed; 31 } 32 getseconds()33 static double getseconds() { 34 return SkTime::GetMSecs() * 0.001; 35 } 36 37 // returns +1 or -1, depending on the sign of x 38 // returns +1 if x is zero SkScalarSign(SkScalar x)39 static SkScalar SkScalarSign(SkScalar x) { 40 SkScalar sign = SK_Scalar1; 41 if (x < 0) { 42 sign = -sign; 43 } 44 return sign; 45 } 46 unit_axis_align(SkVector * unit)47 static void unit_axis_align(SkVector* unit) { 48 const SkScalar TOLERANCE = SkDoubleToScalar(0.15); 49 if (SkScalarAbs(unit->fX) < TOLERANCE) { 50 unit->fX = 0; 51 unit->fY = SkScalarSign(unit->fY); 52 } else if (SkScalarAbs(unit->fY) < TOLERANCE) { 53 unit->fX = SkScalarSign(unit->fX); 54 unit->fY = 0; 55 } 56 } 57 reset(float sx,float sy)58 void FlingState::reset(float sx, float sy) { 59 fActive = true; 60 fDirection.set(sx, sy); 61 fSpeed0 = SkPoint::Normalize(&fDirection); 62 fSpeed0 = pin_max_fling(fSpeed0); 63 fTime0 = getseconds(); 64 65 unit_axis_align(&fDirection); 66 // printf("---- speed %g dir %g %g\n", fSpeed0, fDirection.fX, fDirection.fY); 67 } 68 evaluateMatrix(SkMatrix * matrix)69 bool FlingState::evaluateMatrix(SkMatrix* matrix) { 70 if (!fActive) { 71 return false; 72 } 73 74 const float t = getseconds() - fTime0; 75 const float MIN_SPEED = 2; 76 const float K0 = 5.0; 77 const float K1 = 0.02; 78 const float speed = fSpeed0 * (sk_float_exp(- K0 * t) - K1); 79 if (speed <= MIN_SPEED) { 80 fActive = false; 81 return false; 82 } 83 float dist = (fSpeed0 - speed) / K0; 84 85 // printf("---- time %g speed %g dist %g\n", t, speed, dist); 86 float tx = fDirection.fX * dist; 87 float ty = fDirection.fY * dist; 88 if (DISCRETIZE_TRANSLATE_TO_AVOID_FLICKER) { 89 tx = sk_float_round2int(tx); 90 ty = sk_float_round2int(ty); 91 } 92 matrix->setTranslate(tx, ty); 93 // printf("---- evaluate (%g %g)\n", tx, ty); 94 95 return true; 96 } 97 98 //////////////////////////////////////// 99 GrAnimateFloat()100 GrAnimateFloat::GrAnimateFloat() : fTime0(0) {} 101 start(float v0,float v1,float duration)102 void GrAnimateFloat::start(float v0, float v1, float duration) { 103 fValue0 = v0; 104 fValue1 = v1; 105 fDuration = duration; 106 if (duration > 0) { 107 fTime0 = SkTime::GetMSecs(); 108 if (!fTime0) { 109 fTime0 = 1; // time0 is our sentinel 110 } 111 } else { 112 fTime0 = 0; 113 } 114 } 115 evaluate()116 float GrAnimateFloat::evaluate() { 117 if (!fTime0) { 118 return fValue1; 119 } 120 121 double elapsed = (SkTime::GetMSecs() - fTime0) * 0.001; 122 if (elapsed >= fDuration) { 123 fTime0 = 0; 124 return fValue1; 125 } 126 127 double t = elapsed / fDuration; 128 if (true) { 129 t = (3 - 2 * t) * t * t; 130 } 131 return fValue0 + t * (fValue1 - fValue0); 132 } 133 134 135