Mac, Cocoa: add support for device pixel scrolling (wheel event)

This patch makes use of the rather hidden API on Mac for
accessing the new mouse wheel event type. This will make
scrolling with Mighty Mouse or TrackPad look much more
slick.

Rev-By: prasanth

1 files changed, 25 insertions, 10 deletions

diff --git a/src/gui/kernel/qcocoaview_mac.mm b/src/gui/kernel/qcocoaview_mac.mm
index 7693ca771f..4ebf8a99fa 100644
--- a/src/gui/kernel/qcocoaview_mac.mm
+++ b/src/gui/kernel/qcocoaview_mac.mm
@@ -63,6 +63,11 @@
 
 #include <qdebug.h>
 
+@interface NSEvent (DeviceDelta)
+  - (float)deviceDeltaX;
+  - (float)deviceDeltaY;
+  - (float)deviceDeltaZ;
+@end
 
 QT_BEGIN_NAMESPACE
 
@@ -776,17 +781,27 @@ extern "C" {
     Qt::MouseButton buttons = cocoaButton2QtButton([theEvent buttonNumber]);
     bool wheelOK = false;
     Qt::KeyboardModifiers keyMods = qt_cocoaModifiers2QtModifiers([theEvent modifierFlags]);
-
     QWidget *widgetToGetMouse = qwidget;
-
-    // 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;
-    //                                              The qMax(...) factor reduces the
-    //                                              acceleration for large wheel deltas.
-    int deltaX = [theEvent deltaX] * ScrollFactor * qMax(0.6, 1.1 - qAbs([theEvent deltaX]));
-    int deltaY = [theEvent deltaY] * ScrollFactor * qMax(0.6, 1.1 - qAbs([theEvent deltaY]));
-    int deltaZ = [theEvent deltaZ] * ScrollFactor * qMax(0.6, 1.1 - qAbs([theEvent deltaZ]));
+    int deltaX = 0;
+    int deltaY = 0;
+    int deltaZ = 0;
+
+    const EventRef carbonEvent = (EventRef)[theEvent eventRef];
+    const UInt32 carbonEventKind = carbonEvent ? ::GetEventKind(carbonEvent) : 0;
+    if (carbonEventKind == kEventMouseScroll) {
+        // The mouse device containts pixel scroll
+        // wheel support (Mighty Mouse, Trackpad)
+        deltaX = (int)[theEvent deviceDeltaX] * 120;
+        deltaY = (int)[theEvent deviceDeltaY] * 120;
+        deltaZ = (int)[theEvent deviceDeltaZ] * 120;
+    } 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 * qMax(0.6, 1.1 - qAbs([theEvent deltaX]));
+        deltaY = [theEvent deltaY] * scrollFactor * qMax(0.6, 1.1 - qAbs([theEvent deltaY]));
+        deltaZ = [theEvent deltaZ] * scrollFactor * qMax(0.6, 1.1 - qAbs([theEvent deltaZ]));
+    }
 
     if (deltaX != 0) {
         QWheelEvent qwe(qlocal, qglobal, deltaX, buttons, keyMods, Qt::Horizontal);