/* ============================================================================
**
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** This file is part of the demos of the Qt Toolkit.
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** Alternatively, this file may be used under the terms of the GNU Lesser
** General Public License version 2.1 or version 3 as published by the Free
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============================================================================ */
#define RNC_NO_QT_WEBKIT
#include "flickcharm.h"
#include <QAbstractScrollArea>
#include <QApplication>
#include <QBasicTimer>
#include <QCursor>
#include <QDebug>
#include <QElapsedTimer>
#include <QEvent>
#include <QHash>
#include <QList>
#include <QMouseEvent>
#include <QScrollBar>
#include <QTime>
#ifndef RNC_NO_QT_WEBKIT
#include <QWebFrame>
#include <QWebView>
#endif
#include "common/preprocessor_aid.h" // IWYU pragma: keep
const int fingerAccuracyThreshold = 3;
struct FlickData {
enum class State {
Steady, // Interaction without scrolling
ManualScroll, // Scrolling manually with the finger on the screen
AutoScroll, // Scrolling automatically
AutoScrollAcceleration // Scrolling automatically but a finger is on the screen
};
State state = State::Steady;
QWidget* widget = nullptr;
QPoint pressPos;
QPoint lastPos;
QPoint speed;
QElapsedTimer speedTimer;
QList<QEvent*> ignored;
QElapsedTimer accelerationTimer;
bool lastPosValid:1;
bool waitingAcceleration:1;
FlickData() :
lastPosValid(false),
waitingAcceleration(false)
{}
void resetSpeed()
{
speed = QPoint();
lastPosValid = false;
}
void updateSpeed(const QPoint& newPosition)
{
if (lastPosValid) {
const int timeElapsed = speedTimer.elapsed();
if (timeElapsed) {
const QPoint newPixelDiff = (newPosition - lastPos);
const QPoint pixelsPerSecond = newPixelDiff * (1000 / timeElapsed);
// fingers are inacurates, we ignore small changes to avoid stopping the autoscroll because
// of a small horizontal offset when scrolling vertically
const int newSpeedY = (qAbs(pixelsPerSecond.y()) > fingerAccuracyThreshold)
? pixelsPerSecond.y() : 0;
const int newSpeedX = (qAbs(pixelsPerSecond.x()) > fingerAccuracyThreshold)
? pixelsPerSecond.x() : 0;
if (state == State::AutoScrollAcceleration) {
const int max = 4000; // px by seconds
const int oldSpeedY = speed.y();
const int oldSpeedX = speed.x();
// Was this:
// if ((oldSpeedY <= 0 && newSpeedY <= 0) || (oldSpeedY >= 0 && newSpeedY >= 0)
// && (oldSpeedX <= 0 && newSpeedX <= 0) || (oldSpeedX >= 0 && newSpeedX >= 0)) {
if ((oldSpeedY <= 0 && newSpeedY <= 0) ||
((oldSpeedY >= 0 && newSpeedY >= 0)
&& (oldSpeedX <= 0 && newSpeedX <= 0)) ||
(oldSpeedX >= 0 && newSpeedX >= 0)) {
// RNC: this was A || B && C || D.
// gcc flags that up as a warning ("suggest parentheses
// around '&&' within '||'), very sensibly.
// So should it be A || (B && C) || D, or
// (A || B) && (C || D)?
// Let's assume that it was correct to start with; the
// C++ operator precedence is && above ||.
speed.setY(qBound(-max, (oldSpeedY + (newSpeedY / 4)), max));
speed.setX(qBound(-max, (oldSpeedX + (newSpeedX / 4)), max));
} else {
speed = QPoint();
}
} else {
const int max = 2500; // px by seconds
// we average the speed to avoid strange effects with the last delta
if (!speed.isNull()) {
speed.setX(qBound(-max, (speed.x() / 4) + (newSpeedX * 3 / 4), max));
speed.setY(qBound(-max, (speed.y() / 4) + (newSpeedY * 3 / 4), max));
} else {
speed = QPoint(newSpeedX, newSpeedY);
}
}
}
} else {
lastPosValid = true;
}
speedTimer.start();
lastPos = newPosition;
}
// scroll by dx, dy
// return true if the widget was scrolled
bool scrollWidget(const int dx, const int dy)
{
auto scrollArea = qobject_cast<QAbstractScrollArea*>(widget);
if (scrollArea) {
const int x = scrollArea->horizontalScrollBar()->value();
const int y = scrollArea->verticalScrollBar()->value();
scrollArea->horizontalScrollBar()->setValue(x - dx);
scrollArea->verticalScrollBar()->setValue(y - dy);
return (scrollArea->horizontalScrollBar()->value() != x
|| scrollArea->verticalScrollBar()->value() != y);
}
#ifndef RNC_NO_QT_WEBKIT
QWebView* webView = qobject_cast<QWebView*>(widget);
if (webView) {
QWebFrame* frame = webView->page()->mainFrame();
const QPoint position = frame->scrollPosition();
frame->setScrollPosition(position - QPoint(dx, dy));
return frame->scrollPosition() != position;
}
#endif
return false;
}
bool scrollTo(const QPoint& newPosition)
{
const QPoint delta = newPosition - lastPos;
updateSpeed(newPosition);
return scrollWidget(delta.x(), delta.y());
}
};
class FlickCharmPrivate
{
public:
QHash<QWidget*, FlickData*> flickData;
QBasicTimer ticker;
QElapsedTimer timeCounter;
void startTicker(QObject* object)
{
if (!ticker.isActive()) {
ticker.start(15, object);
}
timeCounter.start();
}
};
FlickCharm::FlickCharm(QObject* parent): QObject(parent)
{
d = new FlickCharmPrivate;
}
FlickCharm::~FlickCharm()
{
delete d;
}
void FlickCharm::activateOn(QWidget* widget)
{
auto scrollArea = qobject_cast<QAbstractScrollArea*>(widget);
if (scrollArea) {
scrollArea->setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
scrollArea->setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
QWidget* viewport = scrollArea->viewport();
viewport->installEventFilter(this);
scrollArea->installEventFilter(this);
d->flickData.remove(viewport);
d->flickData[viewport] = new FlickData;
d->flickData[viewport]->widget = widget;
d->flickData[viewport]->state = FlickData::State::Steady;
return;
}
#ifndef RNC_NO_QT_WEBKIT
QWebView* webView = qobject_cast<QWebView*>(widget);
if (webView) {
QWebFrame* frame = webView->page()->mainFrame();
frame->setScrollBarPolicy(Qt::Vertical, Qt::ScrollBarAlwaysOff);
frame->setScrollBarPolicy(Qt::Horizontal, Qt::ScrollBarAlwaysOff);
webView->installEventFilter(this);
d->flickData.remove(webView);
d->flickData[webView] = new FlickData;
d->flickData[webView]->widget = webView;
d->flickData[webView]->state = FlickData::Steady;
return;
}
#endif
qWarning() << "FlickCharm only works on QAbstractScrollArea (and derived classes)";
#ifndef RNC_NO_QT_WEBKIT
qWarning() << "or QWebView (and derived classes)";
#endif
}
void FlickCharm::deactivateFrom(QWidget* widget)
{
auto scrollArea = qobject_cast<QAbstractScrollArea*>(widget);
if (scrollArea) {
QWidget* viewport = scrollArea->viewport();
viewport->removeEventFilter(this);
scrollArea->removeEventFilter(this);
delete d->flickData[viewport];
d->flickData.remove(viewport);
return;
}
#ifndef RNC_NO_QT_WEBKIT
QWebView* webView = qobject_cast<QWebView*>(widget);
if (webView) {
webView->removeEventFilter(this);
delete d->flickData[webView];
d->flickData.remove(webView);
return;
}
#endif
}
static QPoint deaccelerate(const QPoint& speed, const int deltatime)
{
const int deltaSpeed = deltatime;
int x = speed.x();
int y = speed.y();
x = (x == 0) ? x : (x > 0) ? qMax(0, x - deltaSpeed) : qMin(0, x + deltaSpeed);
y = (y == 0) ? y : (y > 0) ? qMax(0, y - deltaSpeed) : qMin(0, y + deltaSpeed);
return QPoint(x, y);
}
bool FlickCharm::eventFilter(QObject* object, QEvent* event)
{
if (!object->isWidgetType()) {
return false;
}
const QEvent::Type type = event->type();
switch (type) {
case QEvent::MouseButtonPress:
case QEvent::MouseMove:
case QEvent::MouseButtonRelease:
break;
case QEvent::MouseButtonDblClick: // skip double click
return true;
default:
return false;
}
auto mouseEvent = static_cast<QMouseEvent*>(event);
if (type == QEvent::MouseMove && mouseEvent->buttons() != Qt::LeftButton) {
return false;
}
if (mouseEvent->modifiers() != Qt::NoModifier) {
return false;
}
QWidget* viewport = qobject_cast<QWidget*>(object);
FlickData* data = d->flickData.value(viewport);
if (!viewport || !data || data->ignored.removeAll(event)) {
return false;
}
const QPoint mousePos = mouseEvent->pos();
bool consumed = false;
switch (data->state) {
case FlickData::State::Steady:
if (type == QEvent::MouseButtonPress) {
consumed = true;
data->pressPos = mousePos;
} else if (type == QEvent::MouseButtonRelease) {
consumed = true;
auto event1 = new QMouseEvent(QEvent::MouseButtonPress,
data->pressPos, QCursor::pos(),
Qt::LeftButton, Qt::LeftButton,
Qt::NoModifier);
auto event2 = new QMouseEvent(QEvent::MouseButtonRelease,
data->pressPos, QCursor::pos(),
Qt::LeftButton, Qt::LeftButton,
Qt::NoModifier);
data->ignored << event1;
data->ignored << event2;
QApplication::postEvent(object, event1);
QApplication::postEvent(object, event2);
} else if (type == QEvent::MouseMove) {
consumed = true;
data->scrollTo(mousePos);
const QPoint delta = mousePos - data->pressPos;
if (delta.x() > fingerAccuracyThreshold ||
delta.y() > fingerAccuracyThreshold) {
data->state = FlickData::State::ManualScroll;
}
}
break;
case FlickData::State::ManualScroll:
if (type == QEvent::MouseMove) {
consumed = true;
data->scrollTo(mousePos);
} else if (type == QEvent::MouseButtonRelease) {
consumed = true;
data->state = FlickData::State::AutoScroll;
data->lastPosValid = false;
d->startTicker(this);
}
break;
case FlickData::State::AutoScroll:
if (type == QEvent::MouseButtonPress) {
consumed = true;
data->state = FlickData::State::AutoScrollAcceleration;
data->waitingAcceleration = true;
data->accelerationTimer.start();
data->updateSpeed(mousePos);
data->pressPos = mousePos;
} else if (type == QEvent::MouseButtonRelease) {
consumed = true;
data->state = FlickData::State::Steady;
data->resetSpeed();
}
break;
case FlickData::State::AutoScrollAcceleration:
if (type == QEvent::MouseMove) {
consumed = true;
data->updateSpeed(mousePos);
data->accelerationTimer.start();
if (data->speed.isNull()) {
data->state = FlickData::State::ManualScroll;
}
} else if (type == QEvent::MouseButtonRelease) {
consumed = true;
data->state = FlickData::State::AutoScroll;
data->waitingAcceleration = false;
data->lastPosValid = false;
}
break;
#ifdef COMPILER_WANTS_DEFAULT_IN_EXHAUSTIVE_SWITCH
default:
break;
#endif
}
data->lastPos = mousePos;
// return true; // RNC: commented out; see below
// RNC: return value from eventFilter() is: "if you want to filter the
// event out, i.e. stop it being handled further, return true; otherwise
// return false.
// The Qt implementation was "return true;", which means that "consumed" is
// not used. Should it be "return consumed;"? Yes, think so.
return consumed;
}
void FlickCharm::timerEvent(QTimerEvent* event)
{
int count = 0;
QHashIterator<QWidget*, FlickData*> item(d->flickData);
while (item.hasNext()) {
item.next();
FlickData* data = item.value();
if (data->state == FlickData::State::AutoScrollAcceleration
&& data->waitingAcceleration
&& data->accelerationTimer.elapsed() > 40) {
data->state = FlickData::State::ManualScroll;
data->resetSpeed();
}
if (data->state == FlickData::State::AutoScroll ||
data->state == FlickData::State::AutoScrollAcceleration) {
const int timeElapsed = d->timeCounter.elapsed();
const QPoint delta = (data->speed) * timeElapsed / 1000;
bool hasScrolled = data->scrollWidget(delta.x(), delta.y());
if (data->speed.isNull() || !hasScrolled) {
data->state = FlickData::State::Steady;
} else {
count++;
}
data->speed = deaccelerate(data->speed, timeElapsed);
}
}
if (!count) {
d->ticker.stop();
} else {
d->timeCounter.start();
}
QObject::timerEvent(event);
}