Add support for disabling touch on to enhance scrolling in Cocoa

On Mac/Cocoa, enabling touch on a widget slows down the scrolling
performance of the whole application. It seems Cocoa spends some
time in the background figuring out what to do with the touch
events, and whether or not it should convert them to scroll/wheel
events. Therefore, it makes sense to no subscribe for touch when
the mouse is not over the widget, This patch implements that
strategy, and the effect is huge when tested agains creator.

Rev-By: brad

1 files changed, 23 insertions, 8 deletions

diff --git a/src/gui/kernel/qwidget_mac.mm b/src/gui/kernel/qwidget_mac.mm
index f8254ec..b3450ab 100644
--- a/src/gui/kernel/qwidget_mac.mm
+++ b/src/gui/kernel/qwidget_mac.mm
@@ -2697,8 +2697,6 @@ void QWidgetPrivate::create_sys(WId window, bool initializeWindow, bool destroyO
         setWSGeometry();
     if (destroyid)
         qt_mac_destructView(destroyid);
-    if (q->testAttribute(Qt::WA_AcceptTouchEvents))
-        registerTouchWindow();
 }
 
 /*!
@@ -4981,19 +4979,36 @@ void QWidgetPrivate::registerDropSite(bool on)
 #endif
 }
 
-void QWidgetPrivate::registerTouchWindow()
+void QWidgetPrivate::registerTouchWindow(bool enable)
 {
+#ifdef QT_MAC_USE_COCOA
 #if MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_6
     if (QSysInfo::MacintoshVersion < QSysInfo::MV_10_6)
         return;
+
     Q_Q(QWidget);
-    if (!q->testAttribute(Qt::WA_WState_Created))
+    if (enable == touchEventsEnabled)
         return;
-#ifndef QT_MAC_USE_COCOA
-    // Needs implementation!
+
+    QCocoaView *view = static_cast<QCocoaView *>(qt_mac_effectiveview_for(q));
+    if (!view)
+        return;
+
+    if (enable) {
+        ++view->alienTouchCount;
+        if (view->alienTouchCount == 1) {
+            touchEventsEnabled = true;
+            [view setAcceptsTouchEvents:YES];
+        }
+    } else {
+        --view->alienTouchCount;
+        if (view->alienTouchCount == 0) {
+            touchEventsEnabled = false;
+            [view setAcceptsTouchEvents:NO];
+        }
+    }
 #else
-    NSView *view = qt_mac_effectiveview_for(q);
-    [view setAcceptsTouchEvents:YES];
+    Q_UNUSED(on);
 #endif
 #endif
 }