Scroll the parent mouse areas when reaching the bounds of a ScrollView

Change-Id: I18da235e81fa7547b78b623257226dd4a745b518
Reviewed-by: J-P Nurmi <jpnurmi@digia.com>

2 files changed, 40 insertions, 1 deletions

diff --git a/src/controls/Private/qquickwheelarea.cpp b/src/controls/Private/qquickwheelarea.cpp
index e276247b..5fb3e4a6 100644
--- a/src/controls/Private/qquickwheelarea.cpp
+++ b/src/controls/Private/qquickwheelarea.cpp
@@ -77,6 +77,26 @@ QQuickWheelArea::~QQuickWheelArea()
 
 }
 
+bool QQuickWheelArea::isAtXEnd() const
+{
+    return qFuzzyCompare(m_horizontalMaximumValue, m_horizontalValue);
+}
+
+bool QQuickWheelArea::isAtXBeginning() const
+{
+    return qFuzzyCompare(m_horizontalMinimumValue, m_horizontalValue);
+}
+
+bool QQuickWheelArea::isAtYEnd() const
+{
+    return qFuzzyCompare(m_verticalMaximumValue, m_verticalValue);
+}
+
+bool QQuickWheelArea::isAtYBeginning() const
+{
+    return qFuzzyCompare(m_verticalMinimumValue, m_verticalValue);
+}
+
 void QQuickWheelArea::wheelEvent(QWheelEvent *we)
 {
     if (we->phase() == Qt::ScrollBegin)
@@ -95,7 +115,21 @@ void QQuickWheelArea::wheelEvent(QWheelEvent *we)
         setVerticalDelta(numDegrees.y() / 15.0 * m_scrollSpeed);
     }
 
-    we->accept();
+    // This allows other parent WheelArea's to handle scrolling
+    // For example this allows for ScrollView inside of another ScrollView to work correctly
+    // Once this scrollbar can't scroll anymore, ie it reaches the limits,
+    // it will ignore the scroll event so the parent WheelArea can start scrolling
+    if ((numPixels.x() != 0 || numDegrees.x() != 0) &&
+        m_horizontalMinimumValue <= m_horizontalMaximumValue &&
+        (isAtXBeginning() || isAtXEnd())) {
+        we->ignore();
+    } else if ((numPixels.y() != 0 || numDegrees.y() != 0) &&
+               m_verticalMinimumValue <= m_verticalMaximumValue &&
+               (isAtYBeginning() || isAtYEnd())) {
+        we->ignore();
+    } else {
+        we->accept();
+    }
 }
 
 void QQuickWheelArea::setHorizontalMinimumValue(qreal value)
diff --git a/src/controls/Private/qquickwheelarea_p.h b/src/controls/Private/qquickwheelarea_p.h
index ebaa1453..7f9f2b7e 100644
--- a/src/controls/Private/qquickwheelarea_p.h
+++ b/src/controls/Private/qquickwheelarea_p.h
@@ -97,6 +97,11 @@ public:
 
     void wheelEvent(QWheelEvent *event);
 
+    bool isAtXEnd() const;
+    bool isAtXBeginning() const;
+    bool isAtYEnd() const;
+    bool isAtYBeginning() const;
+
 Q_SIGNALS:
     void verticalValueChanged();
     void horizontalValueChanged();