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flickcharm.cpp Example File
demos/embedded/anomaly/src/flickcharm.cpp

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 #include "flickcharm.h"

 #include <QAbstractScrollArea>
 #include <QApplication>
 #include <QBasicTimer>
 #include <QEvent>
 #include <QHash>
 #include <QList>
 #include <QMouseEvent>
 #include <QScrollBar>
 #include <QWebFrame>
 #include <QWebView>

 #include <QDebug>

 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)
 {
     QAbstractScrollArea *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::Steady;

         return;
     }

     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;
     }

     qWarning() << "FlickCharm only works on QAbstractScrollArea (and derived classes)";
     qWarning() << "or QWebView (and derived classes)";
 }

 void FlickCharm::deactivateFrom(QWidget *widget)
 {
     QAbstractScrollArea *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;
     }

     QWebView *webView = qobject_cast<QWebView*>(widget);
     if (webView) {
         webView->removeEventFilter(this);

         delete d->flickData[webView];
         d->flickData.remove(webView);

         return;
     }
 }

 static QPoint scrollOffset(QWidget *widget)
 {
     int x = 0, y = 0;

     QAbstractScrollArea *scrollArea = qobject_cast<QAbstractScrollArea*>(widget);
     if (scrollArea) {
         x = scrollArea->horizontalScrollBar()->value();
         y = scrollArea->verticalScrollBar()->value();
     }

     QWebView *webView = qobject_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 = qobject_cast<QAbstractScrollArea*>(widget);
     if (scrollArea) {
         scrollArea->horizontalScrollBar()->setValue(p.x());
         scrollArea->verticalScrollBar()->setValue(p.y());
     }

     QWebView *webView = qobject_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 = 0;
     switch (event->type()) {
         case QEvent::MouseButtonPress:
         case QEvent::MouseButtonRelease:
         case QEvent::MouseMove:
             mouseEvent = static_cast<QMouseEvent*>(event);
             break;
     }

     if (!mouseEvent || 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;

     bool consumed = false;
     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);
         }
         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;

     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);
 }


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Qt 4.6.1