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50
51#include "knob.h"
52
53#include <QBrush>
54#include <QTouchEvent>
55
56Knob::Knob()
57 : QGraphicsEllipseItem(-50, -50, 100, 100)
58{
59 setAcceptTouchEvents(true);
60 setBrush(Qt::lightGray);
61
62 QGraphicsEllipseItem *leftItem = new QGraphicsEllipseItem(0, 0, 20, 20, this);
63 leftItem->setPos(ax: -40, ay: -10);
64 leftItem->setBrush(Qt::darkGreen);
65
66 QGraphicsEllipseItem *rightItem = new QGraphicsEllipseItem(0, 0, 20, 20, this);
67 rightItem->setPos(ax: 20, ay: -10);
68 rightItem->setBrush(Qt::darkRed);
69}
70
71bool Knob::sceneEvent(QEvent *event)
72{
73 switch (event->type()) {
74 case QEvent::TouchBegin:
75 case QEvent::TouchUpdate:
76 case QEvent::TouchEnd:
77 {
78 QTouchEvent *touchEvent = static_cast<QTouchEvent *>(event);
79
80 if (touchEvent->touchPoints().count() == 2) {
81 const QTouchEvent::TouchPoint &touchPoint1 = touchEvent->touchPoints().first();
82 const QTouchEvent::TouchPoint &touchPoint2 = touchEvent->touchPoints().last();
83
84 QLineF line1(touchPoint1.lastScenePos(), touchPoint2.lastScenePos());
85 QLineF line2(touchPoint1.scenePos(), touchPoint2.scenePos());
86
87 setTransform(matrix: QTransform().rotate(a: line2.angleTo(l: line1)), combine: true);
88 }
89
90 break;
91 }
92
93 default:
94 return QGraphicsItem::sceneEvent(event);
95 }
96
97 return true;
98}
99

source code of qtbase/examples/widgets/touch/knobs/knob.cpp