Widgets: 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: Id1c39093199519f2794b11560c2c0ded2d52b928
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>

3 files changed, 17 insertions, 13 deletions

diff --git a/src/widgets/styles/qfusionstyle.cpp b/src/widgets/styles/qfusionstyle.cpp
index b15b9701d9..5b6e47e2c6 100644
--- a/src/widgets/styles/qfusionstyle.cpp
+++ b/src/widgets/styles/qfusionstyle.cpp
@@ -1649,7 +1649,7 @@ void QFusionStyle::drawControl(ControlElement element, const QStyleOption *optio
 
             QRect textRect(xpos, y + windowsItemVMargin, w - xm - windowsRightBorder - tab + 1, h - 2 * windowsItemVMargin);
             QRect vTextRect = visualRect(opt->direction, menuitem->rect, textRect);
-            QString s = menuitem->text;
+            QStringRef s(&menuitem->text);
             if (!s.isEmpty()) {                     // draw text
                 p->save();
                 int t = s.indexOf(QLatin1Char('\t'));
@@ -1660,12 +1660,13 @@ void QFusionStyle::drawControl(ControlElement element, const QStyleOption *optio
                 if (t >= 0) {
                     QRect vShortcutRect = visualRect(opt->direction, menuitem->rect,
                                                      QRect(textRect.topRight(), QPoint(menuitem->rect.right(), textRect.bottom())));
+                    const QString textToDraw = s.mid(t + 1).toString();
                     if (dis && !act && proxy()->styleHint(SH_EtchDisabledText, option, widget)) {
                         p->setPen(menuitem->palette.light().color());
-                        p->drawText(vShortcutRect.adjusted(1, 1, 1, 1), text_flags, s.mid(t + 1));
+                        p->drawText(vShortcutRect.adjusted(1, 1, 1, 1), text_flags, textToDraw);
                         p->setPen(discol);
                     }
-                    p->drawText(vShortcutRect, text_flags, s.mid(t + 1));
+                    p->drawText(vShortcutRect, text_flags, textToDraw);
                     s = s.left(t);
                 }
                 QFont font = menuitem->font;
@@ -1680,12 +1681,13 @@ void QFusionStyle::drawControl(ControlElement element, const QStyleOption *optio
                     font.setBold(true);
 
                 p->setFont(font);
+                const QString textToDraw = s.left(t).toString();
                 if (dis && !act && proxy()->styleHint(SH_EtchDisabledText, option, widget)) {
                     p->setPen(menuitem->palette.light().color());
-                    p->drawText(vTextRect.adjusted(1, 1, 1, 1), text_flags, s.left(t));
+                    p->drawText(vTextRect.adjusted(1, 1, 1, 1), text_flags, textToDraw);
                     p->setPen(discol);
                 }
-                p->drawText(vTextRect, text_flags, s.left(t));
+                p->drawText(vTextRect, text_flags, textToDraw);
                 p->restore();
             }
 
diff --git a/src/widgets/styles/qstylesheetstyle.cpp b/src/widgets/styles/qstylesheetstyle.cpp
index 053820e459..44555c3058 100644
--- a/src/widgets/styles/qstylesheetstyle.cpp
+++ b/src/widgets/styles/qstylesheetstyle.cpp
@@ -3679,7 +3679,7 @@ void QStyleSheetStyle::drawControl(ControlElement ce, const QStyleOption *opt, Q
 
                 QRect textRect = subRule.contentsRect(opt->rect);
                 textRect.setWidth(textRect.width() - mi.tabWidth);
-                QString s = mi.text;
+                QStringRef s(&mi.text);
                 p->setPen(mi.palette.buttonText().color());
                 if (!s.isEmpty()) {
                     int text_flags = Qt::AlignLeft | Qt::AlignVCenter | Qt::TextShowMnemonic | Qt::TextDontClip | Qt::TextSingleLine;
@@ -3689,10 +3689,10 @@ void QStyleSheetStyle::drawControl(ControlElement ce, const QStyleOption *opt, Q
                     if (t >= 0) {
                         QRect vShortcutRect = visualRect(opt->direction, mi.rect,
                             QRect(textRect.topRight(), QPoint(mi.rect.right(), textRect.bottom())));
-                        p->drawText(vShortcutRect, text_flags, s.mid(t + 1));
+                        p->drawText(vShortcutRect, text_flags, s.mid(t + 1).toString());
                         s = s.left(t);
                     }
-                    p->drawText(textRect, text_flags, s.left(t));
+                    p->drawText(textRect, text_flags, s.left(t).toString());
                 }
 
                 if (mi.menuItemType == QStyleOptionMenuItem::SubMenu) {// draw sub menu arrow
diff --git a/src/widgets/styles/qwindowsstyle.cpp b/src/widgets/styles/qwindowsstyle.cpp
index 36aa312ce8..2ef227762b 100644
--- a/src/widgets/styles/qwindowsstyle.cpp
+++ b/src/widgets/styles/qwindowsstyle.cpp
@@ -1198,7 +1198,7 @@ void QWindowsStyle::drawControl(ControlElement ce, const QStyleOption *opt, QPai
             QRect textRect(xpos, y + QWindowsStylePrivate::windowsItemVMargin,
                            w - xm - QWindowsStylePrivate::windowsRightBorder - tab + 1, h - 2 * QWindowsStylePrivate::windowsItemVMargin);
             QRect vTextRect = visualRect(opt->direction, menuitem->rect, textRect);
-            QString s = menuitem->text;
+            QStringRef s(&menuitem->text);
             if (!s.isEmpty()) {                     // draw text
                 p->save();
                 int t = s.indexOf(QLatin1Char('\t'));
@@ -1209,24 +1209,26 @@ void QWindowsStyle::drawControl(ControlElement ce, const QStyleOption *opt, QPai
                 if (t >= 0) {
                     QRect vShortcutRect = visualRect(opt->direction, menuitem->rect,
                         QRect(textRect.topRight(), QPoint(menuitem->rect.right(), textRect.bottom())));
+                    const QString textToDraw = s.mid(t + 1).toString();
                     if (dis && !act && proxy()->styleHint(SH_EtchDisabledText, opt, widget)) {
                         p->setPen(menuitem->palette.light().color());
-                        p->drawText(vShortcutRect.adjusted(1,1,1,1), text_flags, s.mid(t + 1));
+                        p->drawText(vShortcutRect.adjusted(1, 1, 1, 1), text_flags, textToDraw);
                         p->setPen(discol);
                     }
-                    p->drawText(vShortcutRect, text_flags, s.mid(t + 1));
+                    p->drawText(vShortcutRect, text_flags, textToDraw);
                     s = s.left(t);
                 }
                 QFont font = menuitem->font;
                 if (menuitem->menuItemType == QStyleOptionMenuItem::DefaultItem)
                     font.setBold(true);
                 p->setFont(font);
+                const QString textToDraw = s.left(t).toString();
                 if (dis && !act && proxy()->styleHint(SH_EtchDisabledText, opt, widget)) {
                     p->setPen(menuitem->palette.light().color());
-                    p->drawText(vTextRect.adjusted(1,1,1,1), text_flags, s.left(t));
+                    p->drawText(vTextRect.adjusted(1, 1, 1, 1), text_flags, textToDraw);
                     p->setPen(discol);
                 }
-                p->drawText(vTextRect, text_flags, s.left(t));
+                p->drawText(vTextRect, text_flags, textToDraw);
                 p->restore();
             }
             if (menuitem->menuItemType == QStyleOptionMenuItem::SubMenu) {// draw sub menu arrow