QKeySequence: let Private::decodeString() take QString by value

It calls toLower() on it, and the existence of two strings in scope
has already caused some latent bug where sizes of the two were mixed.

Taking by value means we can use the rvalue-version of toLower().
While that does not guarantee no allocations, we can make sure that at
least in QKeySequence::assign(), we hand in unshared data, by using
std::move().

Change-Id: Ic4a18486a6f4528eba36109dec1a47082cf57055
Reviewed-by: Olivier Goffart (Woboq GmbH) <ogoffart@woboq.com>

2 files changed, 5 insertions, 6 deletions

diff --git a/src/gui/kernel/qkeysequence.cpp b/src/gui/kernel/qkeysequence.cpp
index 6d9f0b0417..9a3d1b0d3a 100644
--- a/src/gui/kernel/qkeysequence.cpp
+++ b/src/gui/kernel/qkeysequence.cpp
@@ -1008,7 +1008,6 @@ int QKeySequence::assign(const QString &ks)
 int QKeySequence::assign(const QString &ks, QKeySequence::SequenceFormat format)
 {
     QString keyseq = ks;
-    QString part;
     int n = 0;
     int p = 0, diff = 0;
 
@@ -1033,9 +1032,9 @@ int QKeySequence::assign(const QString &ks, QKeySequence::SequenceFormat format)
                 }
             }
         }
-        part = keyseq.left(-1 == p ? keyseq.length() : p - diff);
+        QString part = keyseq.left(-1 == p ? keyseq.length() : p - diff);
         keyseq = keyseq.right(-1 == p ? 0 : keyseq.length() - (p + 1));
-        d->key[n] = QKeySequencePrivate::decodeString(part, format);
+        d->key[n] = QKeySequencePrivate::decodeString(std::move(part), format);
         ++n;
     }
     return n;
@@ -1061,10 +1060,10 @@ int QKeySequence::decodeString(const QString &str)
     return QKeySequencePrivate::decodeString(str, NativeText);
 }
 
-int QKeySequencePrivate::decodeString(const QString &str, QKeySequence::SequenceFormat format)
+int QKeySequencePrivate::decodeString(QString accel, QKeySequence::SequenceFormat format)
 {
     int ret = 0;
-    QString accel = str.toLower();
+    accel = std::move(accel).toLower();
     bool nativeText = (format == QKeySequence::NativeText);
 
     QVector<QModifKeyName> *gmodifs;
diff --git a/src/gui/kernel/qkeysequence_p.h b/src/gui/kernel/qkeysequence_p.h
index 8ba86c31b8..fbcab5d34e 100644
--- a/src/gui/kernel/qkeysequence_p.h
+++ b/src/gui/kernel/qkeysequence_p.h
@@ -85,7 +85,7 @@ public:
     static QString encodeString(int key, QKeySequence::SequenceFormat format);
     // used in dbusmenu
     Q_GUI_EXPORT static QString keyName(int key, QKeySequence::SequenceFormat format);
-    static int decodeString(const QString &keyStr, QKeySequence::SequenceFormat format);
+    static int decodeString(QString accel, QKeySequence::SequenceFormat format);
 };
 #endif // QT_NO_SHORTCUT