Fix regression in trackpad scroll event handling.

bab29dd76 changed scroll event handling to update
the keyboard modifier state during scroll event streams
and brought back the bug where Qt Creator would suddenly
change the font size if you pressed the command key
while scrolling.

Use momemtumPhase to detect scroll event streams.
momemtumPahse will be NSEventPhaseNone as long as there
are fingers on the trackpad. After liftoff it will
have a different value, and at this point we freeze
the keyboard modifier state until the scroll event
stream has ended.

This approach does not interfere with normal mouse
scroll wheels since momentumPhase is PahseNone for all
such scroll events.

Change-Id: I668ade8e794a97491487c9465366a316a7d6a9c8
Reviewed-by: Gabriel de Dietrich <gabriel.dedietrich@digia.com>

1 files changed, 11 insertions, 10 deletions

diff --git a/src/plugins/platforms/cocoa/qnsview.mm b/src/plugins/platforms/cocoa/qnsview.mm
index ab098b08bf..8813a934bf 100644
--- a/src/plugins/platforms/cocoa/qnsview.mm
+++ b/src/plugins/platforms/cocoa/qnsview.mm
@@ -1026,20 +1026,21 @@ static QTabletEvent::TabletDevice wacomTabletDevice(NSEvent *theEvent)
     NSTimeInterval timestamp = [theEvent timestamp];
     ulong qt_timestamp = timestamp * 1000;
 
-    // Set keyboard modifiers depending on event phase. A two-finger trackpad flick
-    // generates a stream of scroll events. We want the keyboard modifier state to
-    // be the state at the beginning of the flick in order to avoid changing the
-    // interpretation of the events mid-stream. One example of this happening would
-    // be when pressing cmd after scrolling in Qt Creator: not taking the phase into
-    // account causes the end of the event stream to be interpreted as font size changes.
-
 #if MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_7
     if ([theEvent respondsToSelector:@selector(scrollingDeltaX)]) {
-        NSEventPhase phase = [theEvent phase];
-        if (phase == NSEventPhaseBegan || phase == NSEventPhaseNone) {
+        // Prevent keyboard modifier state from changing during scroll event streams.
+        // A two-finger trackpad flick generates a stream of scroll events. We want
+        // the keyboard modifier state to be the state at the beginning of the
+        // flick in order to avoid changing the interpretation of the events
+        // mid-stream. One example of this happening would be when pressing cmd
+        // after scrolling in Qt Creator: not taking the phase into account causes
+        // the end of the event stream to be interpreted as font size changes.
+        NSEventPhase momentumPhase = [theEvent momentumPhase];
+        if (momentumPhase == NSEventPhaseNone) {
             currentWheelModifiers = [QNSView convertKeyModifiers:[theEvent modifierFlags]];
         }
 
+        NSEventPhase phase = [theEvent phase];
         Qt::ScrollPhase ph = Qt::ScrollUpdate;
 #if MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_8
         if (QSysInfo::QSysInfo::MacintoshVersion >= QSysInfo::MV_10_8) {
@@ -1058,7 +1059,7 @@ static QTabletEvent::TabletDevice wacomTabletDevice(NSEvent *theEvent)
 
         QWindowSystemInterface::handleWheelEvent(m_window, qt_timestamp, qt_windowPoint, qt_screenPoint, pixelDelta, angleDelta, currentWheelModifiers, ph);
 
-        if (phase == NSEventPhaseEnded || phase == NSEventPhaseCancelled || phase == NSEventPhaseNone) {
+        if (momentumPhase == NSEventPhaseEnded || momentumPhase == NSEventPhaseCancelled || momentumPhase == NSEventPhaseNone) {
             currentWheelModifiers = Qt::NoModifier;
         }
     } else