Implement support for wheel delta with finer resolution than 15 deg.

At the moment, Qt, in many places, does not really understand that
a mouse wheel, or touch pad, might operate on a much higher
granularity than 15 degrees (that is, a delta of 120). This is clear
disadvantage on mac, since the mighty mouse, and track pad, got a
resolution that is close to 1 degree. This is called pixel scrolling.

This patch first and formost changes the implementation of
QAbstractSlider::wheelEvent to _really_ understand what to do when
delta is less than 120. Rather than accumulate delta until 120
is reached, then scroll with a value equal to:
offset * step * QApplication::wheelScrollLines (default = 3), we
multiply offset directly, before waiting for 120. This means that
event tough offset is below 120, multiplying it with wheelScrollLines
and step will very often give a value over 120, menaing we can scroll
much earlier and _much more_ fined grained. This also fixes some
auto tests that was ifdeffed out because of specialised mac code
written inside this function from before.
(NB: we still plan to introduce a new event for pixel scrolling,
perhaps for Qt-4.7)

Rev-By: Andreas
Rev-By: denis

1 files changed, 12 insertions, 12 deletions

diff --git a/src/gui/kernel/qcocoaview_mac.mm b/src/gui/kernel/qcocoaview_mac.mm
index d49c150..ecc6bc9 100644
--- a/src/gui/kernel/qcocoaview_mac.mm
+++ b/src/gui/kernel/qcocoaview_mac.mm
@@ -795,23 +795,23 @@ extern "C" {
 
     const EventRef carbonEvent = (EventRef)[theEvent eventRef];
     const UInt32 carbonEventKind = carbonEvent ? ::GetEventKind(carbonEvent) : 0;
-    if (carbonEventKind == kEventMouseScroll) {
+    const bool scrollEvent = carbonEventKind == kEventMouseScroll;
+
+    if (scrollEvent) {
         // The mouse device containts pixel scroll wheel support (Mighty Mouse, Trackpad).
         // Since deviceDelta is delivered as pixels rather than degrees, we need to
         // convert from pixels to degrees in a sensible manner.
         // It looks like four degrees per pixel behaves most native.
         // Qt expects the unit for delta to be 1/8 of a degree:
-        const int scrollFactor = 4 * 8;
-        deltaX = (int)[theEvent deviceDeltaX] * scrollFactor;
-        deltaY = (int)[theEvent deviceDeltaY] * scrollFactor;
-        deltaZ = (int)[theEvent deviceDeltaZ] * scrollFactor;
-    } else { // carbonEventKind == kEventMouseWheelMoved
-        // Mouse wheel deltas seem to tick in at increments of 0.1.
-        // Qt widgets expect the delta to be a multiple of 120.
-        const int scrollFactor = 10 * 120;
-        deltaX = [theEvent deltaX] * scrollFactor;
-        deltaY = [theEvent deltaY] * scrollFactor;
-        deltaZ = [theEvent deltaZ] * scrollFactor;
+        deltaX = [theEvent deviceDeltaX];
+        deltaY = [theEvent deviceDeltaY];
+        deltaZ = [theEvent deviceDeltaZ];
+    } else {
+        // carbonEventKind == kEventMouseWheelMoved
+        // Remove acceleration, and use either -120 or 120 as delta:
+        deltaX = qBound(-120, int([theEvent deltaX] * 10000), 120);
+        deltaY = qBound(-120, int([theEvent deltaY] * 10000), 120);
+        deltaZ = qBound(-120, int([theEvent deltaZ] * 10000), 120);
     }
 
     if (deltaX != 0) {