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    41 

    42 #include <QtGui>

    43 

    44 class MyScrollArea : public QAbstractScrollArea

    45 {

    46 public:

    47     MyScrollArea(QWidget *w);

    48     void setWidget(QWidget *w);

    49 

    50 protected:

    51     void scrollContentsBy(int dx, int dy);

    52     void resizeEvent(QResizeEvent *event);

    53 

    54 private:

    55     void updateWidgetPosition();

    56     void updateArea();

    57 

    58     QWidget *widget;

    59 };

    60 

    61 MyScrollArea::MyScrollArea(QWidget *widget)

    62     : QAbstractScrollArea()

    63 {

    64     setWidget(widget);

    65 }

    66 

    67 void MyScrollArea::setWidget(QWidget *w)

    68 {

    69     widget = w;

    70     widget->setParent(viewport());

    71     if (!widget->testAttribute(Qt::WA_Resized))

    72         widget->resize(widget->sizeHint());

    73 

    74     verticalScrollBar()->setValue(0);

    75     verticalScrollBar()->setValue(0);

    76 

    77     updateArea();

    78 }

    79 

    80 void MyScrollArea::updateWidgetPosition()

    81 {

    82 //! [0]

    83     int hvalue = horizontalScrollBar()->value();

    84     int vvalue = verticalScrollBar()->value();

    85     QPoint topLeft = viewport()->rect().topLeft();

    86 

    87     widget->move(topLeft.x() - hvalue, topLeft.y() - vvalue);

    88 //! [0]

    89 }

    90 

    91 void MyScrollArea::scrollContentsBy(int /*dx*/, int /*dy*/)

    92 {

    93     updateWidgetPosition();

    94 }

    95 

    96 void MyScrollArea::updateArea()

    97 {

    98 //! [1]

    99     QSize areaSize = viewport()->size();

   100     QSize  widgetSize = widget->size();

   101 

   102     verticalScrollBar()->setPageStep(widgetSize.height());

   103     horizontalScrollBar()->setPageStep(widgetSize.width());

   104     verticalScrollBar()->setRange(0, widgetSize.height() - areaSize.height());

   105     horizontalScrollBar()->setRange(0, widgetSize.width() - areaSize.width());

   106     updateWidgetPosition();

   107 //! [1]

   108 }

   109 

   110 void MyScrollArea::resizeEvent(QResizeEvent *event)

   111 {

   112     updateArea();

   113 }

   114 

   115 int main(int argv, char **args)

   116 {

   117     QApplication app(argv, args);

   118 

   119     QPixmap pixmap("mypixmap.png");

   120     QLabel label;

   121     label.setPixmap(pixmap);

   122     MyScrollArea area(&label);

   123     area.resize(300, 300);

   124     area.show();

   125     

   126     area.setWidget(&label);

   127 

   128     return app.exec();

   129 }