qt 6.5.1 original

examples/widgets/touch/knobs/knob.cpp

@@ -0,0 +1,51 @@
+// Copyright (C) 2016 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
+
+#include "knob.h"
+
+#include <QBrush>
+#include <QTouchEvent>
+
+Knob::Knob()
+    : QGraphicsEllipseItem(-50, -50, 100, 100)
+{
+    setAcceptTouchEvents(true);
+    setBrush(Qt::lightGray);
+
+    QGraphicsEllipseItem *leftItem = new QGraphicsEllipseItem(0, 0, 20, 20, this);
+    leftItem->setPos(-40, -10);
+    leftItem->setBrush(Qt::darkGreen);
+
+    QGraphicsEllipseItem *rightItem = new QGraphicsEllipseItem(0, 0, 20, 20, this);
+    rightItem->setPos(20, -10);
+    rightItem->setBrush(Qt::darkRed);
+}
+
+bool Knob::sceneEvent(QEvent *event)
+{
+    switch (event->type()) {
+    case QEvent::TouchBegin:
+    case QEvent::TouchUpdate:
+    case QEvent::TouchEnd:
+    {
+        QTouchEvent *touchEvent = static_cast<QTouchEvent *>(event);
+
+        if (touchEvent->points().count() == 2) {
+            const QEventPoint &touchPoint1 = touchEvent->points().first();
+            const QEventPoint &touchPoint2 = touchEvent->points().last();
+
+            QLineF line1(touchPoint1.sceneLastPosition(), touchPoint2.sceneLastPosition());
+            QLineF line2(touchPoint1.scenePosition(), touchPoint2.scenePosition());
+
+            setTransform(QTransform().rotate(line2.angleTo(line1)), true);
+        }
+
+        break;
+    }
+
+    default:
+        return QGraphicsItem::sceneEvent(event);
+    }
+
+    return true;
+}