Increase fine-grained signals for some properties in Flickable

Flickable.at[X/Y][Beginning/End] were being always notified of changes
at bulk. This is can be harmful in performance of QML applications that
will trigger change requests on the program whenever a property is
modified.

This introduces separate signals so it's not a problem anymore.

Change-Id: I729852df665ec34f532812dd0a45507d053d624c
Reviewed-by: Frederik Gladhorn <frederik.gladhorn@qt.io>

4 files changed, 34 insertions, 10 deletions

diff --git a/src/quick/items/qquickflickable.cpp b/src/quick/items/qquickflickable.cpp
index de3f835dc0..83d383d7c0 100644
--- a/src/quick/items/qquickflickable.cpp
+++ b/src/quick/items/qquickflickable.cpp
@@ -509,7 +509,8 @@ static bool fuzzyLessThanOrEqualTo(qreal a, qreal b)
 void QQuickFlickablePrivate::updateBeginningEnd()
 {
     Q_Q(QQuickFlickable);
-    bool atBoundaryChange = false;
+    bool atXBeginningChange = false, atXEndChange = false;
+    bool atYBeginningChange = false, atYEndChange = false;
 
     // Vertical
     const qreal maxyextent = -q->maxYExtent();
@@ -520,11 +521,11 @@ void QQuickFlickablePrivate::updateBeginningEnd()
 
     if (atBeginning != vData.atBeginning) {
         vData.atBeginning = atBeginning;
-        atBoundaryChange = true;
+        atYBeginningChange = true;
     }
     if (atEnd != vData.atEnd) {
         vData.atEnd = atEnd;
-        atBoundaryChange = true;
+        atYEndChange = true;
     }
 
     // Horizontal
@@ -536,11 +537,11 @@ void QQuickFlickablePrivate::updateBeginningEnd()
 
     if (atBeginning != hData.atBeginning) {
         hData.atBeginning = atBeginning;
-        atBoundaryChange = true;
+        atXBeginningChange = true;
     }
     if (atEnd != hData.atEnd) {
         hData.atEnd = atEnd;
-        atBoundaryChange = true;
+        atXEndChange = true;
     }
 
     if (vData.extentsChanged) {
@@ -561,8 +562,16 @@ void QQuickFlickablePrivate::updateBeginningEnd()
         }
     }
 
-    if (atBoundaryChange)
+    if (atXEndChange || atYEndChange || atXBeginningChange || atYBeginningChange)
         emit q->isAtBoundaryChanged();
+    if (atXEndChange)
+        emit q->atXEndChanged();
+    if (atXBeginningChange)
+        emit q->atXBeginningChanged();
+    if (atYEndChange)
+        emit q->atYEndChanged();
+    if (atYBeginningChange)
+        emit q->atYBeginningChanged();
 
     if (visibleArea)
         visibleArea->updateVisible();
diff --git a/src/quick/items/qquickflickable_p.h b/src/quick/items/qquickflickable_p.h
index 45921c8b86..1bd8fc1020 100644
--- a/src/quick/items/qquickflickable_p.h
+++ b/src/quick/items/qquickflickable_p.h
@@ -98,10 +98,10 @@ class Q_QUICK_PRIVATE_EXPORT QQuickFlickable : public QQuickItem
     Q_PROPERTY(bool interactive READ isInteractive WRITE setInteractive NOTIFY interactiveChanged)
     Q_PROPERTY(int pressDelay READ pressDelay WRITE setPressDelay NOTIFY pressDelayChanged)
 
-    Q_PROPERTY(bool atXEnd READ isAtXEnd NOTIFY isAtBoundaryChanged)
-    Q_PROPERTY(bool atYEnd READ isAtYEnd NOTIFY isAtBoundaryChanged)
-    Q_PROPERTY(bool atXBeginning READ isAtXBeginning NOTIFY isAtBoundaryChanged)
-    Q_PROPERTY(bool atYBeginning READ isAtYBeginning NOTIFY isAtBoundaryChanged)
+    Q_PROPERTY(bool atXEnd READ isAtXEnd NOTIFY atXEndChanged)
+    Q_PROPERTY(bool atYEnd READ isAtYEnd NOTIFY atYEndChanged)
+    Q_PROPERTY(bool atXBeginning READ isAtXBeginning NOTIFY atXBeginningChanged)
+    Q_PROPERTY(bool atYBeginning READ isAtYBeginning NOTIFY atYBeginningChanged)
 
     Q_PROPERTY(QQuickFlickableVisibleArea *visibleArea READ visibleArea CONSTANT)
 
@@ -267,6 +267,11 @@ Q_SIGNALS:
     Q_REVISION(9) void horizontalOvershootChanged();
     Q_REVISION(9) void verticalOvershootChanged();
 
+    Q_REVISION(12) void atXEndChanged();
+    Q_REVISION(12) void atYEndChanged();
+    Q_REVISION(12) void atXBeginningChanged();
+    Q_REVISION(12) void atYBeginningChanged();
+
 protected:
     bool childMouseEventFilter(QQuickItem *, QEvent *) override;
     void mousePressEvent(QMouseEvent *event) override;
diff --git a/src/quick/items/qquickitemsmodule.cpp b/src/quick/items/qquickitemsmodule.cpp
index 3a42766667..c8550af7cc 100644
--- a/src/quick/items/qquickitemsmodule.cpp
+++ b/src/quick/items/qquickitemsmodule.cpp
@@ -431,6 +431,7 @@ static void qt_quickitems_defineModule(const char *uri, int major, int minor)
     qmlRegisterType<QQuickAnimatedImage, 11>(uri, 2, 11,"AnimatedImage");
 #endif
     qmlRegisterType<QQuickItem, 11>(uri, 2, 11,"Item");
+    qmlRegisterType<QQuickFlickable, 12>(uri, 2, 12, "Flickable");
 
     // classes related to Input Handlers which are newly exposed since 5.12
     qmlRegisterUncreatableType<QQuickPointerEvent>(uri, 2, 12, "PointerEvent",
diff --git a/tests/auto/quick/qquickflickable/tst_qquickflickable.cpp b/tests/auto/quick/qquickflickable/tst_qquickflickable.cpp
index ba266824e6..965ef6987a 100644
--- a/tests/auto/quick/qquickflickable/tst_qquickflickable.cpp
+++ b/tests/auto/quick/qquickflickable/tst_qquickflickable.cpp
@@ -1919,6 +1919,10 @@ void tst_qquickflickable::stopAtBounds()
     else
         QCOMPARE(transpose ? flickable->isAtYBeginning() : flickable->isAtXBeginning(), true);
 
+    QSignalSpy atXBeginningChangedSpy(flickable, &QQuickFlickable::atXBeginningChanged);
+    QSignalSpy atYBeginningChangedSpy(flickable, &QQuickFlickable::atYBeginningChanged);
+    QSignalSpy atXEndChangedSpy(flickable, &QQuickFlickable::atXEndChanged);
+    QSignalSpy atYEndChangedSpy(flickable, &QQuickFlickable::atYEndChanged);
     // drag back towards boundary
     for (int i = 0; i < 24; ++i) {
         axis += invert ? threshold / 3 : -threshold / 3;
@@ -1930,6 +1934,11 @@ void tst_qquickflickable::stopAtBounds()
     else
         QCOMPARE(transpose ? flickable->isAtYBeginning() : flickable->isAtXBeginning(), false);
 
+    QCOMPARE(atXBeginningChangedSpy.count(), (!transpose && !invert) ? 1 : 0);
+    QCOMPARE(atYBeginningChangedSpy.count(), ( transpose && !invert) ? 1 : 0);
+    QCOMPARE(atXEndChangedSpy.count(),       (!transpose &&  invert) ? 1 : 0);
+    QCOMPARE(atYEndChangedSpy.count(),       ( transpose &&  invert) ? 1 : 0);
+
     // Drag away from the aligned boundary again.
     // None of the mouse movements will position the view at the boundary exactly,
     // but the view should end up aligned on the boundary