Scrolling bug of mouse wheel operation.

With the mouse control panel of Windows OS
When you set the operation of one wheel scroll of the mouse every one page.
The bug occurs.
If wheel scroll up is executed, it becomes operation that is the down scrolling.
It is generated by all scrolling widget.

This bug seems to have begun to occur from version Qt4.6.
The composition of function had changed compared with version Qt4.5 when the source was confirmed.

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qabstractslider.cpp

bool QAbstractSliderPrivate::scrollByDelta(Qt::Orientation orientation, Qt::KeyboardModifiers modifiers, int delta)
----------------------------------
The description by above-mentioned function is a cause where the bug occurs.

Detailed explanation.
-----------------------------------------------------
qreal stepsToScrollF =
#ifndef QT_NO_WHEELEVENT
QApplication::wheelScrollLines() *
#endif
offset * effectiveSingleStep();

--------------------------------------------------------
Cause of bug concrete the above-mentioned code.

When you set the wheel operation by the setting of the mouse of windows OS every one page

QApplication::wheelScrollLines() => 2147483647

The malfunction is caused so that a very big value may enter QApplication::wheelScrollLines().

When wheel scroll up is executed, contents of the variable "StepsToScroll" should be the values of the minus.
However, the variable "StepsToScroll" reaches the value of the plus because of the mis-operation.

An easy method of settlement is described in the following.
-------------------------------------------------------
qreal stepsToScrollF =
#ifndef QT_NO_WHEELEVENT
(QApplication::wheelScrollLines()<=10000?QApplication::wheelScrollLines():10000) *
#endif
offset * effectiveSingleStep();
-------------------------------------------------------

The value limited to 10000 is returned when QApplication::wheelScrollLines() is more than the value of 10000.