QWheelEvent high-resolution delta support.

Support pixel-based deltas as well as sending
dx and dy values in the same event. Keep source and
behavior compatibility with Qt 4.

New API:
QPoint pixelDelta() const
QPoint angleDelta() const

Deprecate delta() and orientation().

Both pixel-based deltas and combined updates are
necessary for smooth trackpad-based scrolling on
OS X.

Qt 4 compatible behavior is achieved by sending an
extra wheel event in cases where the initial event
has a combined dx and dy update. This extra event
sends dx in delta() and orientation(), with pixelDelta()
and angleDelta() set to null.

Modify the Cocoa implementation to provide pixel
deltas. It is expected that not all platforms can
provide these. Angle deltas will always be available.

Change-Id: I20c10f0df338ddcd6a3f7a4d40949ed5ae3b4795
Reviewed-by: Morten Johan Sørvig <morten.sorvig@nokia.com>

1 files changed, 25 insertions, 23 deletions

diff --git a/src/plugins/platforms/cocoa/qnsview.mm b/src/plugins/platforms/cocoa/qnsview.mm
index 577e0751c6..a43b3fe893 100644
--- a/src/plugins/platforms/cocoa/qnsview.mm
+++ b/src/plugins/platforms/cocoa/qnsview.mm
@@ -371,14 +371,11 @@ static QTouchDevice *touchDevice = 0;
 #ifndef QT_NO_WHEELEVENT
 - (void)scrollWheel:(NSEvent *)theEvent
 {
-    int deltaX = 0;
-    int deltaY = 0;
-    int deltaZ = 0;
-
     const EventRef carbonEvent = (EventRef)[theEvent eventRef];
     const UInt32 carbonEventKind = carbonEvent ? ::GetEventKind(carbonEvent) : 0;
     const bool scrollEvent = carbonEventKind == kEventMouseScroll;
 
+    QPoint angleDelta;
     if (scrollEvent) {
         // The mouse device contains pixel scroll wheel support (Mighty Mouse, Trackpad).
         // Since deviceDelta is delivered as pixels rather than degrees, we need to
@@ -389,40 +386,45 @@ static QTouchDevice *touchDevice = 0;
 
 #if MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_7
         if ([theEvent respondsToSelector:@selector(scrollingDeltaX)]) {
-            deltaX = [theEvent scrollingDeltaX] * pixelsToDegrees;
-            deltaY = [theEvent scrollingDeltaY] * pixelsToDegrees;
-            //  scrollingDeltaZ API is missing.
+            angleDelta.setX([theEvent scrollingDeltaX] * pixelsToDegrees);
+            angleDelta.setY([theEvent scrollingDeltaY] * pixelsToDegrees);
         } else
 #endif
         {
-            deltaX = [theEvent deviceDeltaX] * pixelsToDegrees;
-            deltaY = [theEvent deviceDeltaY] * pixelsToDegrees;
-            deltaZ = [theEvent deviceDeltaZ] * pixelsToDegrees;
+            angleDelta.setX([theEvent deviceDeltaX] * pixelsToDegrees);
+            angleDelta.setY([theEvent deviceDeltaY] * pixelsToDegrees);
         }
 
     } 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);
+        angleDelta.setX(qBound(-120, int([theEvent deltaX] * 10000), 120));
+        angleDelta.setY(qBound(-120, int([theEvent deltaY] * 10000), 120));
     }
 
+    QPoint pixelDelta;
+#if MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_7
+    if ([theEvent respondsToSelector:@selector(scrollingDeltaX)]) {
+        if ([theEvent hasPreciseScrollingDeltas]) {
+            pixelDelta.setX([theEvent scrollingDeltaX]);
+            pixelDelta.setY([theEvent scrollingDeltaY]);
+        } else {
+            // docs: "In the case of !hasPreciseScrollingDeltas, multiply the delta with the line width."
+            // scrollingDeltaX seems to return a minimum value of 0.1 in this case, map that to two pixels.
+            const CGFloat lineWithEstimate = 20.0;
+            pixelDelta.setX([theEvent scrollingDeltaX] * lineWithEstimate);
+            pixelDelta.setY([theEvent scrollingDeltaY] * lineWithEstimate);
+        }
+    }
+#endif
+
+
     NSPoint windowPoint = [self convertPoint: [theEvent locationInWindow] fromView: nil];
     QPoint qt_windowPoint(windowPoint.x, windowPoint.y);
     NSTimeInterval timestamp = [theEvent timestamp];
     ulong qt_timestamp = timestamp * 1000;
 
-    if (deltaX != 0)
-        QWindowSystemInterface::handleWheelEvent(m_window, qt_timestamp, qt_windowPoint, qt_windowPoint, deltaX, Qt::Horizontal);
-
-    if (deltaY != 0)
-        QWindowSystemInterface::handleWheelEvent(m_window, qt_timestamp, qt_windowPoint, qt_windowPoint, deltaY, Qt::Vertical);
-
-    if (deltaZ != 0)
-        // Qt doesn't explicitly support wheels with a Z component. In a misguided attempt to
-        // try to be ahead of the pack, I'm adding this extra value.
-        QWindowSystemInterface::handleWheelEvent(m_window, qt_timestamp, qt_windowPoint, qt_windowPoint, deltaY, (Qt::Orientation)3);
+    QWindowSystemInterface::handleWheelEvent(m_window, qt_timestamp, qt_windowPoint, qt_windowPoint, pixelDelta, angleDelta);
 }
 #endif //QT_NO_WHEELEVENT