Mac: scroll speed does not match native applications

It turns out that we limit wheel scrolling on mac to an
upper limit per event to one page. This behaviour is a bit
strange in the first place, and on mac, it is just wrong.
Besides, even when this limitation is removed, we still scroll
a bit slower that native. The 'problem' is to come up with a
good conversion from pixel scrolling to line based
scrolling (Qt does not really have an API for pixel scrolling).
But we up the speed a bit to make it perform more similar to
xcode.

Rev-by: msorvig

1 files changed, 8 insertions, 0 deletions

diff --git a/src/gui/widgets/qabstractslider.cpp b/src/gui/widgets/qabstractslider.cpp
index 2888490..522d472 100644
--- a/src/gui/widgets/qabstractslider.cpp
+++ b/src/gui/widgets/qabstractslider.cpp
@@ -712,7 +712,15 @@ bool QAbstractSliderPrivate::scrollByDelta(Qt::Orientation orientation, Qt::Keyb
             offset_accumulated = 0;
 
         offset_accumulated += stepsToScrollF;
+#ifndef Q_WS_MAC
+        // Dont't scroll more than one page in any case:
         stepsToScroll = qBound(-pageStep, int(offset_accumulated), pageStep);
+#else
+        // Native UI-elements on Mac can scroll hundreds of lines at a time as
+        // a result of acceleration. So keep the same behaviour in Qt, and
+        // dont restrict stepsToScroll to certain maximum (pageStep): 
+        stepsToScroll = int(offset_accumulated);
+#endif
         offset_accumulated -= int(offset_accumulated);
         if (stepsToScroll == 0)
             return false;