QGestureManager: fix expensive iteration over QHash::keys()

... with iteration over the hash itself.

gesturesByType is a local variable, so there's no way
functions called in the loop can modify it.

This dividing operation would greatly benefit from
a splice operation in QHash...

Change-Id: Ifd241d2da9c6998c2ad0b08294fca84d5b188d0f
Reviewed-by: Olivier Goffart (Woboq GmbH) <ogoffart@woboq.com>

1 files changed, 4 insertions, 3 deletions

diff --git a/src/widgets/kernel/qgesturemanager.cpp b/src/widgets/kernel/qgesturemanager.cpp
index 533ed6ac81..8cb7c2b560 100644
--- a/src/widgets/kernel/qgesturemanager.cpp
+++ b/src/widgets/kernel/qgesturemanager.cpp
@@ -571,7 +571,8 @@ void QGestureManager::getGestureTargets(const QSet<QGesture*> &gestures,
     // for each gesture type
     for (GestureByTypes::const_iterator git = gestureByTypes.cbegin(), gend = gestureByTypes.cend(); git != gend; ++git) {
         const QHash<QWidget *, QGesture *> &gestures = git.value();
-        foreach (QWidget *widget, gestures.keys()) {
+        for (QHash<QWidget *, QGesture *>::const_iterator wit = gestures.cbegin(), wend = gestures.cend(); wit != wend; ++wit) {
+            QWidget *widget = wit.key();
             QWidget *w = widget->parentWidget();
             while (w) {
                 QMap<Qt::GestureType, Qt::GestureFlags>::const_iterator it
@@ -580,7 +581,7 @@ void QGestureManager::getGestureTargets(const QSet<QGesture*> &gestures,
                     // i.e. 'w' listens to gesture 'type'
                     if (!(it.value() & Qt::DontStartGestureOnChildren) && w != widget) {
                         // conflicting gesture!
-                        (*conflicts)[widget].append(gestures[widget]);
+                        (*conflicts)[widget].append(wit.value());
                         break;
                     }
                 }
@@ -591,7 +592,7 @@ void QGestureManager::getGestureTargets(const QSet<QGesture*> &gestures,
                 w = w->parentWidget();
             }
             if (!w)
-                (*normal)[widget].append(gestures[widget]);
+                (*normal)[widget].append(wit.value());
         }
     }
 }