QtGui: use QStringRef to optimize memory allocation

Replace substring functions that return QString with
corresponding functions that return QStringRef where
it's possible.

Create QString from QStringRef only where necessary.

Change-Id: Id83c60cc7568b20ef008b51c582cfdf466a47e35
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>

3 files changed, 8 insertions, 9 deletions

diff --git a/src/gui/text/qcssparser.cpp b/src/gui/text/qcssparser.cpp
index d455a74d96..c237d80d34 100644
--- a/src/gui/text/qcssparser.cpp
+++ b/src/gui/text/qcssparser.cpp
@@ -1510,7 +1510,7 @@ QRect Declaration::rectValue() const
     const QStringList func = v.variant.toStringList();
     if (func.count() != 2 || func.at(0).compare(QLatin1String("rect")) != 0)
         return QRect();
-    QStringList args = func[1].split(QLatin1Char(' '), QString::SkipEmptyParts);
+    const auto args = func[1].splitRef(QLatin1Char(' '), QString::SkipEmptyParts);
     if (args.count() != 4)
         return QRect();
     QRect rect(args[0].toInt(), args[1].toInt(), args[2].toInt(), args[3].toInt());
@@ -1915,9 +1915,8 @@ bool StyleSelector::basicSelectorMatches(const BasicSelector &sel, NodePtr node)
                 return false;
 
             if (a.valueMatchCriterium == QCss::AttributeSelector::MatchContains) {
-
-                QStringList lst = attrValue.split(QLatin1Char(' '));
-                if (!lst.contains(a.value))
+                const auto lst = attrValue.splitRef(QLatin1Char(' '));
+                if (!lst.contains(QStringRef(&a.value)))
                     return false;
             } else if (
                 (a.valueMatchCriterium == QCss::AttributeSelector::MatchEqual
diff --git a/src/gui/text/qfont.cpp b/src/gui/text/qfont.cpp
index f92e4ab457..828dbc318c 100644
--- a/src/gui/text/qfont.cpp
+++ b/src/gui/text/qfont.cpp
@@ -2033,7 +2033,7 @@ uint qHash(const QFont &font, uint seed) Q_DECL_NOTHROW
  */
 bool QFont::fromString(const QString &descrip)
 {
-    QStringList l(descrip.split(QLatin1Char(',')));
+    const auto l = descrip.splitRef(QLatin1Char(','));
 
     int count = l.count();
     if (!count || (count > 2 && count < 9) || count > 11) {
@@ -2042,7 +2042,7 @@ bool QFont::fromString(const QString &descrip)
         return false;
     }
 
-    setFamily(l[0]);
+    setFamily(l[0].toString());
     if (count > 1 && l[1].toDouble() > 0.0)
         setPointSizeF(l[1].toDouble());
     if (count == 9) {
diff --git a/src/gui/text/qfontdatabase.cpp b/src/gui/text/qfontdatabase.cpp
index 359c461ad3..9b50581bea 100644
--- a/src/gui/text/qfontdatabase.cpp
+++ b/src/gui/text/qfontdatabase.cpp
@@ -697,15 +697,15 @@ static QStringList familyList(const QFontDef &req)
     if (req.family.isEmpty())
         return family_list;
 
-    QStringList list = req.family.split(QLatin1Char(','));
+    const auto list = req.family.splitRef(QLatin1Char(','));
     const int numFamilies = list.size();
     family_list.reserve(numFamilies);
     for (int i = 0; i < numFamilies; ++i) {
-        QString str = list.at(i).trimmed();
+        QStringRef str = list.at(i).trimmed();
         if ((str.startsWith(QLatin1Char('"')) && str.endsWith(QLatin1Char('"')))
             || (str.startsWith(QLatin1Char('\'')) && str.endsWith(QLatin1Char('\''))))
             str = str.mid(1, str.length() - 2);
-        family_list << str;
+        family_list << str.toString();
     }
 
     // append the substitute list for each family in family_list