QGraphicsAnchorLayout: replace three loops over QHash::keys() with QHash::const_iterator loops

Quite obviously faster (doesn't need to populate a QList first,
just to iterate over it).

Also saves 1.5KiB text on optimized GCC 4.9 Linux AMD64 builds.

Change-Id: If4c7af80165a6027d39359bac22df30e7ca09815
Reviewed-by: Olivier Goffart (Woboq GmbH) <ogoffart@woboq.com>
Reviewed-by: Lars Knoll <lars.knoll@theqtcompany.com>

1 files changed, 5 insertions, 3 deletions

diff --git a/src/widgets/graphicsview/qsimplex_p.cpp b/src/widgets/graphicsview/qsimplex_p.cpp
index b827ab1400..d4e2e2f922 100644
--- a/src/widgets/graphicsview/qsimplex_p.cpp
+++ b/src/widgets/graphicsview/qsimplex_p.cpp
@@ -153,9 +153,11 @@ bool QSimplex::setConstraints(const QList<QSimplexConstraint *> &newConstraints)
     // "variables" is a list that provides a stable, indexed list of all variables
     // used in this problem.
     QSet<QSimplexVariable *> variablesSet;
-    for (int i = 0; i < constraints.size(); ++i)
-        variablesSet += \
-            QSet<QSimplexVariable *>::fromList(constraints[i]->variables.keys());
+    for (int i = 0; i < constraints.size(); ++i) {
+        const auto &v = constraints.at(i)->variables;
+        for (auto it = v.cbegin(), end = v.cend(); it != end; ++it)
+            variablesSet.insert(it.key());
+    }
     variables = variablesSet.toList();
 
     // Set Variables reverse mapping