Make PinchArea translate correctly inside a rotated parent

Also includes 9dacc312e5b0f5aeb0f8370f4f7722b57754a3c2:
fuzzy comparison in the test to avoid failure due to roundoff.

Fixes: QTBUG-63673
Change-Id: I91231bb8555b7eb02a9580f9f184b261d8bd44c8
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@qt.io>
(cherry picked from commit 7642205be45135add120373299df02e05f4ffc58)
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>

3 files changed, 143 insertions, 1 deletions

diff --git a/src/quick/items/qquickpincharea.cpp b/src/quick/items/qquickpincharea.cpp
index b41815d88b..ed8506b440 100644
--- a/src/quick/items/qquickpincharea.cpp
+++ b/src/quick/items/qquickpincharea.cpp
@@ -563,7 +563,10 @@ void QQuickPinchArea::updatePinch(QTouchEvent *event, bool filtering)
                         setKeepTouchGrab(true);
                         d->inPinch = true;
                         if (d->pinch && d->pinch->target()) {
-                            d->pinchStartPos = pinch()->target()->position();
+                            auto targetParent = pinch()->target()->parentItem();
+                            d->pinchStartPos = targetParent ?
+                                        targetParent->mapToScene(pinch()->target()->position()) :
+                                        pinch()->target()->position();
                             d->pinchStartScale = d->pinch->target()->scale();
                             d->pinchStartRotation = d->pinch->target()->rotation();
                             d->pinch->setActive(true);
@@ -611,6 +614,9 @@ void QQuickPinchArea::updatePinchTarget()
         s = qMin(qMax(pinch()->minimumScale(),s), pinch()->maximumScale());
         pinch()->target()->setScale(s);
         QPointF pos = d->sceneLastCenter - d->sceneStartCenter + d->pinchStartPos;
+        if (auto targetParent = pinch()->target()->parentItem())
+            pos = targetParent->mapFromScene(pos);
+
         if (pinch()->axis() & QQuickPinch::XAxis) {
             qreal x = pos.x();
             if (x < pinch()->xmin())
diff --git a/tests/auto/quick/qquickpincharea/data/draggablePinchArea.qml b/tests/auto/quick/qquickpincharea/data/draggablePinchArea.qml
new file mode 100644
index 0000000000..3acf67b4b6
--- /dev/null
+++ b/tests/auto/quick/qquickpincharea/data/draggablePinchArea.qml
@@ -0,0 +1,70 @@
+import QtQuick 2.12
+
+Rectangle {
+    id: root
+    width: 600
+    height: 600
+
+    Rectangle {
+        objectName: "paContainer"
+        width: parent.width -100
+        height: parent.height - 100
+        border.color: "black"
+        anchors.centerIn: parent
+        transformOrigin: Item.Center
+
+        Rectangle {
+            width: 300
+            height: 300
+            color: "tomato"
+            PinchArea {
+                id: pa
+                anchors.fill: parent
+                pinch.target: parent
+                pinch.minimumScale: 0.5
+                pinch.maximumScale: 2
+                pinch.minimumRotation: -360
+                pinch.maximumRotation: 360
+                pinch.dragAxis: Pinch.XAndYAxis
+                pinch.minimumX: -100
+                pinch.maximumX: 300
+                pinch.minimumY: -100
+                pinch.maximumY: 300
+            }
+
+
+            Text { text: "this way up" }
+        }
+    }
+
+    // only for touch feedback / troubleshooting
+    Item {
+        id: glassPane
+        z: 10000
+        anchors.fill: parent
+
+        PointHandler {
+            id: ph1
+            target: Rectangle {
+                parent: glassPane
+                color: "green"
+                visible: ph1.active
+                x: ph1.point.position.x - width / 2
+                y: ph1.point.position.y - height / 2
+                width: 20; height: width; radius: width / 2
+            }
+        }
+
+        PointHandler {
+            id: ph2
+            target: Rectangle {
+                parent: glassPane
+                color: "blue"
+                visible: ph2.active
+                x: ph2.point.position.x - width / 2
+                y: ph2.point.position.y - height / 2
+                width: 20; height: width; radius: width / 2
+            }
+        }
+    }
+}
diff --git a/tests/auto/quick/qquickpincharea/tst_qquickpincharea.cpp b/tests/auto/quick/qquickpincharea/tst_qquickpincharea.cpp
index a9f35e8727..55fb07f744 100644
--- a/tests/auto/quick/qquickpincharea/tst_qquickpincharea.cpp
+++ b/tests/auto/quick/qquickpincharea/tst_qquickpincharea.cpp
@@ -52,6 +52,8 @@ private slots:
     void cancel();
     void transformedPinchArea_data();
     void transformedPinchArea();
+    void dragTransformedPinchArea_data();
+    void dragTransformedPinchArea();
 
 private:
     QQuickView *createView();
@@ -576,6 +578,70 @@ void tst_QQuickPinchArea::transformedPinchArea()
     }
 }
 
+void tst_QQuickPinchArea::dragTransformedPinchArea_data()
+{
+    QTest::addColumn<int>("rotation");
+    QTest::addColumn<QPoint>("p1");
+    QTest::addColumn<QPoint>("p2");
+    QTest::addColumn<QPoint>("delta");
+
+    QTest::newRow("unrotated")
+            << 0 << QPoint(100, 100) << QPoint(200, 100) << QPoint(40, 40);
+    QTest::newRow("20 deg")
+            << 20 << QPoint(100, 100) << QPoint(200, 100) << QPoint(40, 40);
+    QTest::newRow("90 deg")
+            << 90 << QPoint(100, 100) << QPoint(200, 100) << QPoint(0, 40);
+    QTest::newRow("180 deg")
+            << 180 << QPoint(100, 100) << QPoint(200, 100) << QPoint(40, 0);
+    QTest::newRow("225 deg")
+            << 210 << QPoint(200, 200) << QPoint(300, 200) << QPoint(80, 80);
+}
+
+void tst_QQuickPinchArea::dragTransformedPinchArea() // QTBUG-63673
+{
+    QFETCH(int, rotation);
+    QFETCH(QPoint, p1);
+    QFETCH(QPoint, p2);
+    QFETCH(QPoint, delta);
+    const int threshold = qApp->styleHints()->startDragDistance();
+
+    QQuickView *view = createView();
+    QScopedPointer<QQuickView> scope(view);
+    view->setSource(testFileUrl("draggablePinchArea.qml"));
+    view->show();
+    QVERIFY(QTest::qWaitForWindowExposed(view));
+    QVERIFY(view->rootObject());
+    QQuickPinchArea *pinchArea = view->rootObject()->findChild<QQuickPinchArea*>();
+    QVERIFY(pinchArea);
+    QQuickItem *pinchAreaTarget = pinchArea->parentItem();
+    QVERIFY(pinchAreaTarget);
+    QQuickItem *pinchAreaContainer = pinchAreaTarget->parentItem();
+    QVERIFY(pinchAreaContainer);
+    pinchAreaContainer->setRotation(rotation);
+
+    QTest::QTouchEventSequence pinchSequence = QTest::touchEvent(view, device);
+    // start pinch
+    pinchSequence.press(1, pinchArea->mapToScene(p1).toPoint(), view)
+                 .press(2, pinchArea->mapToScene(p2).toPoint(), view).commit();
+    QQuickTouchUtils::flush(view);
+    pinchSequence.move(1, pinchArea->mapToScene(p1 + QPoint(threshold, threshold)).toPoint(), view)
+                 .move(2, pinchArea->mapToScene(p2 + QPoint(threshold, threshold)).toPoint(), view).commit();
+    QQuickTouchUtils::flush(view);
+    pinchSequence.move(1, pinchArea->mapToScene(p1 + delta).toPoint(), view)
+                 .move(2, pinchArea->mapToScene(p2 + delta).toPoint(), view).commit();
+    QQuickTouchUtils::flush(view);
+    QCOMPARE(pinchArea->pinch()->active(), true);
+    auto error = delta - QPoint(threshold, threshold) -
+                pinchAreaTarget->position().toPoint(); // expect 0, 0
+    QVERIFY(qAbs(error.x()) <= 1);
+    QVERIFY(qAbs(error.y()) <= 1);
+
+    // release pinch
+    pinchSequence.release(1, p1, view).release(2, p2, view).commit();
+    QQuickTouchUtils::flush(view);
+    QCOMPARE(pinchArea->pinch()->active(), false);
+}
+
 QQuickView *tst_QQuickPinchArea::createView()
 {
     QQuickView *window = new QQuickView(nullptr);