Carbon: better wheel acceleration patch

It turns out that scrolling appears to be slow when using
non-mac mice with the carbon build. This patch introduces a
an acceleration algorithm that closer resembles the one
used by Cocoa.

Rev-By: prasanth

2 files changed, 23 insertions, 6 deletions

diff --git a/src/gui/kernel/qapplication_mac.mm b/src/gui/kernel/qapplication_mac.mm
index a95ae9d..f9c8aa3 100644
--- a/src/gui/kernel/qapplication_mac.mm
+++ b/src/gui/kernel/qapplication_mac.mm
@@ -1708,12 +1708,30 @@ QApplicationPrivate::globalEventProcessor(EventHandlerCallRef er, EventRef event
                         sizeof(axis), 0, &axis);
 
                 // The 'new' event has acceleration applied by the OS, while the old (on
-                // Carbon only), has not. So we introduce acceleration here to be consistent:
-                int scrollFactor = 120 * qMin(5, qAbs(mdelt));
+                // Carbon only), has not. So we introduce acceleration here to be consistent.
+                // The acceleration is trying to respect both pixel based and line scrolling,
+                // which turns out to be rather difficult.
+                int linesToScroll = mdelt > 0 ? 1 : -1;
+                static QTime t;
+                int elapsed = t.elapsed();
+                t.restart();
+                if (elapsed < 20)
+                    linesToScroll *= 120;
+                else if (elapsed < 30)
+                    linesToScroll *= 60;
+                else if (elapsed < 50)
+                    linesToScroll *= 30;
+                else if (elapsed < 100)
+                    linesToScroll *= 6;
+                else if (elapsed < 200)
+                    linesToScroll *= 3;
+                else if (elapsed < 300)
+                    linesToScroll *= 2;
+
                 if (axis == kEventMouseWheelAxisX)
-                    wheel_deltaX = mdelt * scrollFactor;
+                    wheel_deltaX = linesToScroll * 120;
                 else
-                    wheel_deltaY = mdelt * scrollFactor;
+                    wheel_deltaY = linesToScroll * 120;
             }
         }
 
diff --git a/src/gui/widgets/qabstractslider.cpp b/src/gui/widgets/qabstractslider.cpp
index 19a8b63..588a48e 100644
--- a/src/gui/widgets/qabstractslider.cpp
+++ b/src/gui/widgets/qabstractslider.cpp
@@ -715,8 +715,7 @@ void QAbstractSlider::wheelEvent(QWheelEvent * e)
 #else
         stepsToScroll = int(d->offset_accumulated) * QApplication::wheelScrollLines() * d->singleStep;
 #endif
-        if (qAbs(stepsToScroll) > d->pageStep)
-            stepsToScroll = currentOffset > 0 ? d->pageStep : -d->pageStep;
+        stepsToScroll = qBound(-d->pageStep, stepsToScroll, d->pageStep);
     }
 
     if (d->invertedControls)