flickcharm.cpp

/****************************************************************************
**
** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
** Contact: Qt Software Information (qt-info@nokia.com)
**
** This file is part of the Graphics Dojo project on Qt Labs.
**
** This file may be used under the terms of the GNU General Public
** License version 2.0 or 3.0 as published by the Free Software Foundation
** and appearing in the file LICENSE.GPL included in the packaging of
** this file.  Please review the following information to ensure GNU
** General Public Licensing requirements will be met:
** http://www.fsf.org/licensing/licenses/info/GPLv2.html and
** http://www.gnu.org/copyleft/gpl.html.
**
** If you are unsure which license is appropriate for your use, please
** contact the sales department at qt-sales@nokia.com.
**
** This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
** WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
**
****************************************************************************/
#include "flickcharm.h"
#include <QAbstractScrollArea>
#include <QApplication>
#include <QBasicTimer>
#include <QEvent>
#include <QHash>
#include <QList>
#include <QMouseEvent>
#include <QScrollBar>
//Requires QT += webkit
//#include <QWebFrame>
//#include <QWebView>
#include <QDebug>

const int fingerAccuracyThreshold = 10;

struct FlickData {
    typedef enum { Steady, Pressed, ManualScroll, AutoScroll, Stop } State;
    State state;
    QWidget *widget;
    QPoint pressPos;
    QPoint offset;
    QPoint dragPos;
    QPoint speed;
    QList<QEvent*> ignored;
};
class FlickCharmPrivate
{
public:
    QHash<QWidget*, FlickData*> flickData;
    QBasicTimer ticker;
};
FlickCharm::FlickCharm(QObject *parent): QObject(parent)
{
    d = new FlickCharmPrivate;
}
FlickCharm::~FlickCharm()
{
    delete d;
}
void FlickCharm::activateOn(QWidget *widget)
{
#if defined(Q_OS_SYMBIAN) || defined(Q_OS_WINCE)
    QAbstractScrollArea *scrollArea = dynamic_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::Steady;
        return;
    }
//    QWebView *webView = dynamic_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;
//    }

    qWarning() << "FlickCharm only works on QAbstractScrollArea (and derived classes)";
//    qWarning() << "or QWebView (and derived classes)";
#endif
}
void FlickCharm::deactivateFrom(QWidget *widget)
{
#if defined(Q_OS_SYMBIAN) || defined(Q_OS_WINCE)
    QAbstractScrollArea *scrollArea = dynamic_cast<QAbstractScrollArea*>(widget);
    if (scrollArea) {
        QWidget *viewport = scrollArea->viewport();
        viewport->removeEventFilter(this);
        scrollArea->removeEventFilter(this);
        delete d->flickData[viewport];
        d->flickData.remove(viewport);
        return;
    }
//    QWebView *webView = dynamic_cast<QWebView*>(widget);
//    if (webView) {
//        webView->removeEventFilter(this);
//        delete d->flickData[webView];
//        d->flickData.remove(webView);
//        return;
//    }
#endif
}
static QPoint scrollOffset(QWidget *widget)
{
    int x = 0, y = 0;
    QAbstractScrollArea *scrollArea = dynamic_cast<QAbstractScrollArea*>(widget);
    if (scrollArea) {
        x = scrollArea->horizontalScrollBar()->value();
        y = scrollArea->verticalScrollBar()->value();
    }
//    QWebView *webView = dynamic_cast<QWebView*>(widget);
//    if (webView) {
//        QWebFrame *frame = webView->page()->mainFrame();
//        x = frame->evaluateJavaScript("window.scrollX").toInt();
//        y = frame->evaluateJavaScript("window.scrollY").toInt();
//    }
    return QPoint(x, y);
}
static void setScrollOffset(QWidget *widget, const QPoint &p)
{
    QAbstractScrollArea *scrollArea = dynamic_cast<QAbstractScrollArea*>(widget);
    if (scrollArea) {
        scrollArea->horizontalScrollBar()->setValue(p.x());
        scrollArea->verticalScrollBar()->setValue(p.y());
    }
//    QWebView *webView = dynamic_cast<QWebView*>(widget);
//    QWebFrame *frame = webView ? webView->page()->mainFrame() : 0;
//    if (frame)
//        frame->evaluateJavaScript(QString("window.scrollTo(%1,%2);").arg(p.x()).arg(p.y()));
}
static QPoint deaccelerate(const QPoint &speed, int a = 1, int max = 64)
{
    int x = qBound(-max, speed.x(), max);
    int y = qBound(-max, speed.y(), max);
    x = (x == 0) ? x : (x > 0) ? qMax(0, x - a) : qMin(0, x + a);
    y = (y == 0) ? y : (y > 0) ? qMax(0, y - a) : qMin(0, y + a);
    return QPoint(x, y);
}
bool FlickCharm::eventFilter(QObject *object, QEvent *event)
{
    if (!object->isWidgetType())
        return false;
    QEvent::Type type = event->type();
    if (type != QEvent::MouseButtonPress &&
            type != QEvent::MouseButtonRelease &&
            type != QEvent::MouseMove)
        return false;
    QMouseEvent *mouseEvent = dynamic_cast<QMouseEvent*>(event);
    if (!mouseEvent || mouseEvent->modifiers() != Qt::NoModifier)
        return false;
    QWidget *viewport = dynamic_cast<QWidget*>(object);
    FlickData *data = d->flickData.value(viewport);
    if (!viewport || !data || data->ignored.removeAll(event))
        return false;
    bool consumed = false;
    QPoint delta;
    switch (data->state) {
    case FlickData::Steady:
        if (mouseEvent->type() == QEvent::MouseButtonPress)
            if (mouseEvent->buttons() == Qt::LeftButton) {
                consumed = true;
                data->state = FlickData::Pressed;
                data->pressPos = mouseEvent->pos();
                data->offset = scrollOffset(data->widget);
            }
        break;
    case FlickData::Pressed:
        if (mouseEvent->type() == QEvent::MouseButtonRelease) {
            consumed = true;
            data->state = FlickData::Steady;
            QMouseEvent *event1 = new QMouseEvent(QEvent::MouseButtonPress,
                                                  data->pressPos, Qt::LeftButton,
                                                  Qt::LeftButton, Qt::NoModifier);
            QMouseEvent *event2 = new QMouseEvent(*mouseEvent);
            data->ignored << event1;
            data->ignored << event2;
            QApplication::postEvent(object, event1);
            QApplication::postEvent(object, event2);
        }
        delta = data->pressPos - mouseEvent->pos();
        if (mouseEvent->type() == QEvent::MouseMove &&
                (qAbs(delta.x()) > fingerAccuracyThreshold ||
                 qAbs(delta.y()) > fingerAccuracyThreshold)) {
            consumed = true;
            data->state = FlickData::ManualScroll;
            data->dragPos = QCursor::pos();
            if (!d->ticker.isActive())
                d->ticker.start(20, this);
        }
        break;
    case FlickData::ManualScroll:
        if (mouseEvent->type() == QEvent::MouseMove) {
            consumed = true;
            QPoint delta = mouseEvent->pos() - data->pressPos;
            setScrollOffset(data->widget, data->offset - delta);
        }
        if (mouseEvent->type() == QEvent::MouseButtonRelease) {
            consumed = true;
            data->state = FlickData::AutoScroll;
        }
        break;
    case FlickData::AutoScroll:
        if (mouseEvent->type() == QEvent::MouseButtonPress) {
            consumed = true;
            data->state = FlickData::Stop;
            data->speed = QPoint(0, 0);
            data->pressPos = mouseEvent->pos();
            data->offset = scrollOffset(data->widget);
        }
        if (mouseEvent->type() == QEvent::MouseButtonRelease) {
            consumed = true;
            data->state = FlickData::Steady;
            data->speed = QPoint(0, 0);
        }
        break;
    case FlickData::Stop:
        if (mouseEvent->type() == QEvent::MouseButtonRelease) {
            consumed = true;
            data->state = FlickData::Steady;
        }
        if (mouseEvent->type() == QEvent::MouseMove) {
            consumed = true;
            data->state = FlickData::ManualScroll;
            data->dragPos = QCursor::pos();
            if (!d->ticker.isActive())
                d->ticker.start(20, this);
        }
        break;
    default:
        break;
    }
    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::ManualScroll) {
            count++;
            data->speed = QCursor::pos() - data->dragPos;
            data->dragPos = QCursor::pos();
        }
        if (data->state == FlickData::AutoScroll) {
            count++;
            data->speed = deaccelerate(data->speed);
            QPoint p = scrollOffset(data->widget);
            setScrollOffset(data->widget, p - data->speed);
            if (data->speed == QPoint(0, 0))
                data->state = FlickData::Steady;
        }
    }
    if (!count)
        d->ticker.stop();
    QObject::timerEvent(event);
}