Introduce QWheelEvent::Phase (Begin, Changed, Ended)

Some platforms (read: OS X) send wheel events without delta to indicate
that scrolling is about to start or has ended. Currently, Qt simply
ignores wheel events that have no delta. This change introduces a new
QWheelEvent attribute that specifies the phase, and makes it possible
to receive the special wheel events in started/ended phases. These
events are required for implementing correctly behaving transient
scrollbars.

Change-Id: Ib8ce0d9ce9be63b2ad60aa7b0aaa1f12ef6cad09
Reviewed-by: Gabriel de Dietrich <gabriel.dedietrich@digia.com>
Reviewed-by: Shawn Rutledge <shawn.rutledge@digia.com>

1 files changed, 55 insertions, 1 deletions

diff --git a/src/gui/kernel/qevent.cpp b/src/gui/kernel/qevent.cpp
index fa289bbf8b..49cc411c4f 100644
--- a/src/gui/kernel/qevent.cpp
+++ b/src/gui/kernel/qevent.cpp
@@ -654,6 +654,9 @@ QWheelEvent::QWheelEvent(const QPointF &pos, const QPointF& globalPos, int delta
     event data: \a qt4Delta specifies the rotation, and \a qt4Orientation the
     direction.
 
+    The phase() is initialized to QWheelEvent::Changed. Use the other constructor
+    to specify the phase explicitly.
+
     \sa posF(), globalPosF(), angleDelta(), pixelDelta()
 */
 
@@ -661,9 +664,38 @@ QWheelEvent::QWheelEvent(const QPointF &pos, const QPointF& globalPos,
             QPoint pixelDelta, QPoint angleDelta, int qt4Delta, Qt::Orientation qt4Orientation,
             Qt::MouseButtons buttons, Qt::KeyboardModifiers modifiers)
     : QInputEvent(Wheel, modifiers), p(pos), g(globalPos), pixelD(pixelDelta),
-      angleD(angleDelta), qt4D(qt4Delta), qt4O(qt4Orientation), mouseState(buttons)
+      angleD(angleDelta), qt4D(qt4Delta), qt4O(qt4Orientation), mouseState(buttons), ph(Changed)
 {}
 
+/*!
+    Constructs a wheel event object.
+
+    The \a pos provides the location of the mouse cursor
+    within the window. The position in global coordinates is specified
+    by \a globalPos.
+
+    \a pixelDelta contains the scrolling distance in pixels on screen, while
+    \a angleDelta contains the wheel rotation distance. \a pixelDelta is
+    optional and can be null.
+
+    The mouse and keyboard states at the time of the event are specified by
+    \a buttons and \a modifiers.
+
+    For backwards compatibility, the event can also hold monodirectional wheel
+    event data: \a qt4Delta specifies the rotation, and \a qt4Orientation the
+    direction.
+
+    The phase of the event is specified by \a phase.
+
+    \sa posF(), globalPosF(), angleDelta(), pixelDelta(), phase()
+*/
+
+QWheelEvent::QWheelEvent(const QPointF &pos, const QPointF& globalPos,
+            QPoint pixelDelta, QPoint angleDelta, int qt4Delta, Qt::Orientation qt4Orientation,
+            Qt::MouseButtons buttons, Qt::KeyboardModifiers modifiers, Phase phase)
+    : QInputEvent(Wheel, modifiers), p(pos), g(globalPos), pixelD(pixelDelta),
+      angleD(angleDelta), qt4D(qt4Delta), qt4O(qt4Orientation), mouseState(buttons), ph(phase)
+{}
 
 #endif // QT_NO_WHEELEVENT
 
@@ -794,6 +826,28 @@ QWheelEvent::QWheelEvent(const QPointF &pos, const QPointF& globalPos,
     \sa posF()
 */
 
+/*!
+    \enum QWheelEvent::Phase
+    \since 5.2
+
+    This enum describes the phase of a wheel event.
+
+    \value Started Scrolling has started, but the scrolling
+    distance did not yet change.
+
+    \value Changed The scrolling distance has changed (default).
+
+    \value Ended Scrolling has ended, but the scrolling distance
+    did not change anymore.
+*/
+
+/*!
+    \fn QWheelEvent::Phase QWheelEvent::phase() const
+    \since 5.2
+
+    Returns the phase of this wheel event.
+*/
+
 
 /*!
     \class QKeyEvent