summaryrefslogtreecommitdiffstats
path: root/src/declarative/util/qdeclarativespringfollow.cpp
blob: 063c3df4f800af9f230ab12d6115a7e5e1813cdc (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
/****************************************************************************
**
** Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies).
** All rights reserved.
** Contact: Nokia Corporation (qt-info@nokia.com)
**
** This file is part of the QtDeclarative module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** No Commercial Usage
** This file contains pre-release code and may not be distributed.
** You may use this file in accordance with the terms and conditions
** contained in the Technology Preview License Agreement accompanying
** this package.
**
** GNU Lesser General Public License Usage
** Alternatively, this file may be used under the terms of the GNU Lesser
** General Public License version 2.1 as published by the Free Software
** Foundation and appearing in the file LICENSE.LGPL included in the
** packaging of this file.  Please review the following information to
** ensure the GNU Lesser General Public License version 2.1 requirements
** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
**
** In addition, as a special exception, Nokia gives you certain additional
** rights.  These rights are described in the Nokia Qt LGPL Exception
** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
**
** If you have questions regarding the use of this file, please contact
** Nokia at qt-info@nokia.com.
**
**
**
**
**
**
**
**
** $QT_END_LICENSE$
**
****************************************************************************/

#include "qdeclarativespringfollow_p.h"

#include "qdeclarativeanimation_p_p.h"

#include <QtCore/qdebug.h>

#include <private/qobject_p.h>

#include <limits.h>
#include <math.h>

QT_BEGIN_NAMESPACE



class QDeclarativeSpringFollowPrivate : public QObjectPrivate
{
    Q_DECLARE_PUBLIC(QDeclarativeSpringFollow)
public:
    QDeclarativeSpringFollowPrivate()
        : currentValue(0), sourceValue(0), maxVelocity(0), lastTime(0)
        , mass(1.0), spring(0.), damping(0.), velocity(0), epsilon(0.01)
        , modulus(0.0), useMass(false), haveModulus(false), enabled(true), mode(Track), clock(this) {}

    QDeclarativeProperty property;
    qreal currentValue;
    qreal sourceValue;
    qreal maxVelocity;
    qreal velocityms;
    int lastTime;
    qreal mass;
    qreal spring;
    qreal damping;
    qreal velocity;
    qreal epsilon;
    qreal modulus;

    bool useMass : 1;
    bool haveModulus : 1;
    bool enabled : 1;

    enum Mode {
        Track,
        Velocity,
        Spring
    };
    Mode mode;

    void tick(int);
    void updateMode();
    void start();
    void stop();

    QTickAnimationProxy<QDeclarativeSpringFollowPrivate, &QDeclarativeSpringFollowPrivate::tick> clock;
};

void QDeclarativeSpringFollowPrivate::tick(int time)
{
    Q_Q(QDeclarativeSpringFollow);

    int elapsed = time - lastTime;
    if (!elapsed)
        return;
    qreal srcVal = sourceValue;
    if (haveModulus) {
        currentValue = fmod(currentValue, modulus);
        srcVal = fmod(srcVal, modulus);
    }
    if (mode == Spring) {
        if (elapsed < 16) // capped at 62fps.
            return;
        // Real men solve the spring DEs using RK4.
        // We'll do something much simpler which gives a result that looks fine.
        int count = elapsed / 16;
        for (int i = 0; i < count; ++i) {
            qreal diff = srcVal - currentValue;
            if (haveModulus && qAbs(diff) > modulus / 2) {
                if (diff < 0)
                    diff += modulus;
                else
                    diff -= modulus;
            }
            if (useMass)
                velocity = velocity + (spring * diff - damping * velocity) / mass;
            else
                velocity = velocity + spring * diff - damping * velocity;
            if (maxVelocity > 0.) {
                // limit velocity
                if (velocity > maxVelocity)
                    velocity = maxVelocity;
                else if (velocity < -maxVelocity)
                    velocity = -maxVelocity;
            }
            currentValue += velocity * 16.0 / 1000.0;
            if (haveModulus) {
                currentValue = fmod(currentValue, modulus);
                if (currentValue < 0.0)
                    currentValue += modulus;
            }
        }
        if (qAbs(velocity) < epsilon && qAbs(srcVal - currentValue) < epsilon) {
            velocity = 0.0;
            currentValue = srcVal;
            clock.stop();
        }
        lastTime = time - (elapsed - count * 16);
    } else {
        qreal moveBy = elapsed * velocityms;
        qreal diff = srcVal - currentValue;
        if (haveModulus && qAbs(diff) > modulus / 2) {
            if (diff < 0)
                diff += modulus;
            else
                diff -= modulus;
        }
        if (diff > 0) {
            currentValue += moveBy;
            if (haveModulus)
                currentValue = fmod(currentValue, modulus);
            if (currentValue > sourceValue) {
                currentValue = sourceValue;
                clock.stop();
            }
        } else {
            currentValue -= moveBy;
            if (haveModulus && currentValue < 0.0)
                currentValue = fmod(currentValue, modulus) + modulus;
            if (currentValue < sourceValue) {
                currentValue = sourceValue;
                clock.stop();
            }
        }
        lastTime = time;
    }
    property.write(currentValue);
    emit q->valueChanged(currentValue);
    if (clock.state() != QAbstractAnimation::Running)
        emit q->syncChanged();
}

void QDeclarativeSpringFollowPrivate::updateMode()
{
    if (spring == 0. && maxVelocity == 0.)
        mode = Track;
    else if (spring > 0.)
        mode = Spring;
    else
        mode = Velocity;
}

void QDeclarativeSpringFollowPrivate::start()
{
    if (!enabled)
        return;

    Q_Q(QDeclarativeSpringFollow);
    if (mode == QDeclarativeSpringFollowPrivate::Track) {
        currentValue = sourceValue;
        property.write(currentValue);
    } else if (sourceValue != currentValue && clock.state() != QAbstractAnimation::Running) {
        lastTime = 0;
        currentValue = property.read().toReal();
        clock.start(); // infinity??
        emit q->syncChanged();
    }
}

void QDeclarativeSpringFollowPrivate::stop()
{
    clock.stop();
}

/*!
    \qmlclass SpringFollow QDeclarativeSpringFollow
    \since 4.7
    \brief The SpringFollow element allows a property to track a value.

    In example below, \e rect2 will follow \e rect1 moving with a velocity of up to 200:
    \code
    Rectangle {
        id: rect1
        width: 20; height: 20
        color: "#00ff00"
        y: 200  // initial value
        SequentialAnimation on y {
            loops: Animation.Infinite
            NumberAnimation {
                to: 200
                easing.type: "OutBounce"
                easing.amplitude: 100
                duration: 2000
            }
            PauseAnimation { duration: 1000 }
        }
    }
    Rectangle {
        id: rect2
        x: rect1.width
        width: 20; height: 20
        color: "#ff0000"
        SpringFollow on y { source: rect1.y; velocity: 200 }
    }
    \endcode
*/

QDeclarativeSpringFollow::QDeclarativeSpringFollow(QObject *parent)
: QObject(*(new QDeclarativeSpringFollowPrivate),parent)
{
}

QDeclarativeSpringFollow::~QDeclarativeSpringFollow()
{
}

void QDeclarativeSpringFollow::setTarget(const QDeclarativeProperty &property)
{
    Q_D(QDeclarativeSpringFollow);
    d->property = property;
    d->currentValue = property.read().toReal();
}

qreal QDeclarativeSpringFollow::sourceValue() const
{
    Q_D(const QDeclarativeSpringFollow);
    return d->sourceValue;
}

/*!
    \qmlproperty qreal SpringFollow::source
    This property holds the source value which will be tracked.

    Bind to a property in order to track its changes.
*/

void QDeclarativeSpringFollow::setSourceValue(qreal value)
{
    Q_D(QDeclarativeSpringFollow);
    if (d->clock.state() == QAbstractAnimation::Running && d->sourceValue == value)
        return;

    d->sourceValue = value;
    d->start();
}

/*!
    \qmlproperty qreal SpringFollow::velocity
    This property holds the maximum velocity allowed when tracking the source.
*/

qreal QDeclarativeSpringFollow::velocity() const
{
    Q_D(const QDeclarativeSpringFollow);
    return d->maxVelocity;
}

void QDeclarativeSpringFollow::setVelocity(qreal velocity)
{
    Q_D(QDeclarativeSpringFollow);
    d->maxVelocity = velocity;
    d->velocityms = velocity / 1000.0;
    d->updateMode();
}

/*!
    \qmlproperty qreal SpringFollow::spring
    This property holds the spring constant

    The spring constant describes how strongly the target is pulled towards the
    source.  Setting spring to 0 turns off spring tracking.  Useful values 0 - 5.0

    When a spring constant is set and the velocity property is greater than 0,
    velocity limits the maximum speed.
*/
qreal QDeclarativeSpringFollow::spring() const
{
    Q_D(const QDeclarativeSpringFollow);
    return d->spring;
}

void QDeclarativeSpringFollow::setSpring(qreal spring)
{
    Q_D(QDeclarativeSpringFollow);
    d->spring = spring;
    d->updateMode();
}

/*!
    \qmlproperty qreal SpringFollow::damping
    This property holds the spring damping constant

    The damping constant describes how quickly a sprung follower comes to rest.
    Useful range is 0 - 1.0
*/
qreal QDeclarativeSpringFollow::damping() const
{
    Q_D(const QDeclarativeSpringFollow);
    return d->damping;
}

void QDeclarativeSpringFollow::setDamping(qreal damping)
{
    Q_D(QDeclarativeSpringFollow);
    if (damping > 1.)
        damping = 1.;

    d->damping = damping;
}


/*!
    \qmlproperty qreal SpringFollow::epsilon
    This property holds the spring epsilon

    The epsilon is the rate and amount of change in the value which is close enough
    to 0 to be considered equal to zero. This will depend on the usage of the value.
    For pixel positions, 0.25 would suffice. For scale, 0.005 will suffice.

    The default is 0.01. Tuning this value can provide small performance improvements.
*/
qreal QDeclarativeSpringFollow::epsilon() const
{
    Q_D(const QDeclarativeSpringFollow);
    return d->epsilon;
}

void QDeclarativeSpringFollow::setEpsilon(qreal epsilon)
{
    Q_D(QDeclarativeSpringFollow);
    d->epsilon = epsilon;
}

/*!
    \qmlproperty qreal SpringFollow::modulus
    This property holds the modulus value.

    Setting a \a modulus forces the target value to "wrap around" at the modulus.
    For example, setting the modulus to 360 will cause a value of 370 to wrap around to 10.
*/
qreal QDeclarativeSpringFollow::modulus() const
{
    Q_D(const QDeclarativeSpringFollow);
    return d->modulus;
}

void QDeclarativeSpringFollow::setModulus(qreal modulus)
{
    Q_D(QDeclarativeSpringFollow);
    if (d->modulus != modulus) {
        d->haveModulus = modulus != 0.0;
        d->modulus = modulus;
        emit modulusChanged();
    }
}

/*!
    \qmlproperty qreal SpringFollow::mass
    This property holds the "mass" of the property being moved.

    mass is 1.0 by default.  Setting a different mass changes the dynamics of
    a \l spring follow.
*/
qreal QDeclarativeSpringFollow::mass() const
{
    Q_D(const QDeclarativeSpringFollow);
    return d->mass;
}

void QDeclarativeSpringFollow::setMass(qreal mass)
{
    Q_D(QDeclarativeSpringFollow);
    if (d->mass != mass && mass > 0.0) {
        d->useMass = mass != 1.0;
        d->mass = mass;
        emit massChanged();
    }
}

/*!
    \qmlproperty qreal SpringFollow::value
    The current value.
*/

/*!
    \qmlproperty bool SpringFollow::enabled
    This property holds whether the target will track the source.
*/
bool QDeclarativeSpringFollow::enabled() const
{
    Q_D(const QDeclarativeSpringFollow);
    return d->enabled;
}

void QDeclarativeSpringFollow::setEnabled(bool enabled)
{
    Q_D(QDeclarativeSpringFollow);
    d->enabled = enabled;
    if (enabled)
        d->start();
    else
        d->stop();
}

/*!
    \qmlproperty bool SpringFollow::inSync
    This property is true when target is equal to the source; otherwise
    false.  If inSync is true the target is not being animated.

    If \l enabled is false then inSync will also be false.
*/
bool QDeclarativeSpringFollow::inSync() const
{
    Q_D(const QDeclarativeSpringFollow);
    return d->enabled && d->clock.state() != QAbstractAnimation::Running;
}

qreal QDeclarativeSpringFollow::value() const
{
    Q_D(const QDeclarativeSpringFollow);
    return d->currentValue;
}

QT_END_NAMESPACE