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50
51 #include <QtWidgets>
52
53 class MyScrollArea : public QAbstractScrollArea
54 {
55 public:
56 MyScrollArea(QWidget *w);
57 void setWidget(QWidget *w);
58
59 protected:
60 void scrollContentsBy(int dx, int dy) override;
61 void resizeEvent(QResizeEvent *event) override;
62
63 private:
64 void updateWidgetPosition();
65 void updateArea();
66
67 QWidget *widget;
68 };
69
MyScrollArea(QWidget * widget)70 MyScrollArea::MyScrollArea(QWidget *widget)
71 : QAbstractScrollArea()
72 {
73 setWidget(widget);
74 }
75
setWidget(QWidget * w)76 void MyScrollArea::setWidget(QWidget *w)
77 {
78 widget = w;
79 widget->setParent(viewport());
80 if (!widget->testAttribute(Qt::WA_Resized))
81 widget->resize(widget->sizeHint());
82
83 verticalScrollBar()->setValue(0);
84 verticalScrollBar()->setValue(0);
85
86 updateArea();
87 }
88
updateWidgetPosition()89 void MyScrollArea::updateWidgetPosition()
90 {
91 //! [0]
92 int hvalue = horizontalScrollBar()->value();
93 int vvalue = verticalScrollBar()->value();
94 QPoint topLeft = viewport()->rect().topLeft();
95
96 widget->move(topLeft.x() - hvalue, topLeft.y() - vvalue);
97 //! [0]
98 }
99
scrollContentsBy(int dx,int dy)100 void MyScrollArea::scrollContentsBy(int dx, int dy)
101 {
102 Q_UNUSED(dx);
103 Q_UNUSED(dy);
104 updateWidgetPosition();
105 }
106
updateArea()107 void MyScrollArea::updateArea()
108 {
109 //! [1]
110 QSize areaSize = viewport()->size();
111 QSize widgetSize = widget->size();
112
113 verticalScrollBar()->setPageStep(areaSize.height());
114 horizontalScrollBar()->setPageStep(areaSize.width());
115 verticalScrollBar()->setRange(0, widgetSize.height() - areaSize.height());
116 horizontalScrollBar()->setRange(0, widgetSize.width() - areaSize.width());
117 updateWidgetPosition();
118 //! [1]
119 }
120
resizeEvent(QResizeEvent * event)121 void MyScrollArea::resizeEvent(QResizeEvent *event)
122 {
123 Q_UNUSED(event);
124 updateArea();
125 }
126