Add dragThreshold property to Event Handlers

We need drag threshold to be adjustable on each handler instance instead
of relying only on the system default drag threshold. For example in
some use cases DragHandler needs to work with a threshold of 0 or 1 to
start dragging as soon as the point is pressed or as soon as the point
is moved, with no "jump", to enable fine adjustment of a value on some
control such as a Slider.

This involves moving the dragOverThreshold() functions that handlers are
using from QQuickWindowPrivate to QQuickPointerHandlerPrivate, so that
they can use the adjustable threshold value.

Task-number: QTBUG-68075
Change-Id: Ie720cbbf9f30abb40d1731d92f8e7f1e6534eeb5
Reviewed-by: Jan Arve Sæther <jan-arve.saether@qt.io>

1 files changed, 97 insertions, 2 deletions

diff --git a/tests/auto/quick/pointerhandlers/qquickdraghandler/tst_qquickdraghandler.cpp b/tests/auto/quick/pointerhandlers/qquickdraghandler/tst_qquickdraghandler.cpp
index 66314f88a2..65c5ac9ef4 100644
--- a/tests/auto/quick/pointerhandlers/qquickdraghandler/tst_qquickdraghandler.cpp
+++ b/tests/auto/quick/pointerhandlers/qquickdraghandler/tst_qquickdraghandler.cpp
@@ -53,9 +53,12 @@ private slots:
     void initTestCase();
 
     void defaultPropertyValues();
+    void touchDrag_data();
     void touchDrag();
     void mouseDrag_data();
     void mouseDrag();
+    void mouseDragThreshold_data();
+    void mouseDragThreshold();
     void dragFromMargin();
     void snapMode_data();
     void snapMode();
@@ -131,9 +134,18 @@ void tst_DragHandler::defaultPropertyValues()
     QCOMPARE(dragHandler->centroid().sceneGrabPosition(), QPointF());
 }
 
+void tst_DragHandler::touchDrag_data()
+{
+    QTest::addColumn<int>("dragThreshold");
+    QTest::newRow("threshold zero") << 0;
+    QTest::newRow("threshold one") << 1;
+    QTest::newRow("threshold 20") << 20;
+    QTest::newRow("threshold default") << -1;
+}
+
 void tst_DragHandler::touchDrag()
 {
-    const int dragThreshold = QGuiApplication::styleHints()->startDragDistance();
+    QFETCH(int, dragThreshold);
     QScopedPointer<QQuickView> windowPtr;
     createView(windowPtr, "draggables.qml");
     QQuickView * window = windowPtr.data();
@@ -142,6 +154,12 @@ void tst_DragHandler::touchDrag()
     QVERIFY(ball);
     QQuickDragHandler *dragHandler = ball->findChild<QQuickDragHandler*>();
     QVERIFY(dragHandler);
+    if (dragThreshold < 0) {
+        dragThreshold = QGuiApplication::styleHints()->startDragDistance();
+        QCOMPARE(dragHandler->dragThreshold(), dragThreshold);
+    } else {
+        dragHandler->setDragThreshold(dragThreshold);
+    }
 
     QSignalSpy translationChangedSpy(dragHandler, SIGNAL(translationChanged()));
     QSignalSpy centroidChangedSpy(dragHandler, SIGNAL(centroidChanged()));
@@ -161,7 +179,9 @@ void tst_DragHandler::touchDrag()
     p1 += QPoint(dragThreshold, 0);
     QTest::touchEvent(window, touchDevice).move(1, p1, window);
     QQuickTouchUtils::flush(window);
-    QTRY_VERIFY(dragHandler->centroid().velocity().x() > 0);
+    qCDebug(lcPointerTests) << "velocity after drag" << dragHandler->centroid().velocity();
+    if (dragThreshold > 0)
+        QTRY_VERIFY(!qFuzzyIsNull(dragHandler->centroid().velocity().x()));
     QCOMPARE(centroidChangedSpy.count(), 2);
     QVERIFY(!dragHandler->active());
     p1 += QPoint(1, 0);
@@ -282,6 +302,81 @@ void tst_DragHandler::mouseDrag()
     QCOMPARE(centroidChangedSpy.count(), shouldDrag ? 5 : 0);
 }
 
+void tst_DragHandler::mouseDragThreshold_data()
+{
+    QTest::addColumn<int>("dragThreshold");
+    QTest::newRow("threshold zero") << 0;
+    QTest::newRow("threshold one") << 1;
+    QTest::newRow("threshold 20") << 20;
+    QTest::newRow("threshold default") << -1;
+}
+
+void tst_DragHandler::mouseDragThreshold()
+{
+    QFETCH(int, dragThreshold);
+    QScopedPointer<QQuickView> windowPtr;
+    createView(windowPtr, "draggables.qml");
+    QQuickView * window = windowPtr.data();
+
+    QQuickItem *ball = window->rootObject()->childItems().first();
+    QVERIFY(ball);
+    QQuickDragHandler *dragHandler = ball->findChild<QQuickDragHandler*>();
+    QVERIFY(dragHandler);
+    if (dragThreshold < 0) {
+        dragThreshold = QGuiApplication::styleHints()->startDragDistance();
+        QCOMPARE(dragHandler->dragThreshold(), dragThreshold);
+    } else {
+        dragHandler->setDragThreshold(dragThreshold);
+    }
+
+    QSignalSpy translationChangedSpy(dragHandler, SIGNAL(translationChanged()));
+    QSignalSpy centroidChangedSpy(dragHandler, SIGNAL(centroidChanged()));
+
+    QPointF ballCenter = ball->clipRect().center();
+    QPointF scenePressPos = ball->mapToScene(ballCenter);
+    QPoint p1 = scenePressPos.toPoint();
+    QTest::mousePress(window, Qt::LeftButton, Qt::NoModifier, p1);
+    QVERIFY(!dragHandler->active());
+    QCOMPARE(dragHandler->centroid().position(), ballCenter);
+    QCOMPARE(dragHandler->centroid().pressPosition(), ballCenter);
+    QCOMPARE(dragHandler->centroid().scenePosition(), scenePressPos);
+    QCOMPARE(dragHandler->centroid().scenePressPosition(), scenePressPos);
+    QCOMPARE(dragHandler->centroid().velocity(), QVector2D());
+    QCOMPARE(centroidChangedSpy.count(), 1);
+    p1 += QPoint(dragThreshold, 0);
+    QTest::mouseMove(window, p1);
+    if (dragThreshold > 0)
+        QTRY_VERIFY(dragHandler->centroid().velocity().x() > 0);
+    QCOMPARE(centroidChangedSpy.count(), 2);
+    QVERIFY(!dragHandler->active());
+    p1 += QPoint(1, 0);
+    QTest::mouseMove(window, p1);
+    QTRY_VERIFY(dragHandler->active());
+    QCOMPARE(translationChangedSpy.count(), 0);
+    QCOMPARE(centroidChangedSpy.count(), 3);
+    QCOMPARE(dragHandler->translation().x(), 0.0);
+    QPointF sceneGrabPos = p1;
+    QCOMPARE(dragHandler->centroid().sceneGrabPosition(), sceneGrabPos);
+    p1 += QPoint(19, 0);
+    QTest::mouseMove(window, p1);
+    QTRY_VERIFY(dragHandler->active());
+    QCOMPARE(dragHandler->centroid().position(), ballCenter);
+    QCOMPARE(dragHandler->centroid().pressPosition(), ballCenter);
+    QCOMPARE(dragHandler->centroid().scenePosition(), ball->mapToScene(ballCenter));
+    QCOMPARE(dragHandler->centroid().scenePressPosition(), scenePressPos);
+    QCOMPARE(dragHandler->centroid().sceneGrabPosition(), sceneGrabPos);
+    QCOMPARE(dragHandler->translation().x(), dragThreshold + 20.0);
+    QCOMPARE(dragHandler->translation().y(), 0.0);
+    QVERIFY(dragHandler->centroid().velocity().x() > 0);
+    QCOMPARE(centroidChangedSpy.count(), 4);
+    QTest::mouseRelease(window, Qt::LeftButton, Qt::NoModifier, p1);
+    QTRY_VERIFY(!dragHandler->active());
+    QCOMPARE(dragHandler->centroid().pressedButtons(), Qt::NoButton);
+    QCOMPARE(ball->mapToScene(ballCenter).toPoint(), p1);
+    QCOMPARE(translationChangedSpy.count(), 1);
+    QCOMPARE(centroidChangedSpy.count(), 5);
+}
+
 void tst_DragHandler::dragFromMargin() // QTBUG-74966
 {
     const int dragThreshold = QGuiApplication::styleHints()->startDragDistance();