diff --git a/src/canvaswidget.cpp b/src/canvaswidget.cpp
index 644c3fa..343fece 100644
--- a/src/canvaswidget.cpp
+++ b/src/canvaswidget.cpp
@@ -1,158 +1,158 @@
 /*
     Copyright 2012 Viranch Mehta <viranch.mehta@gmail.com>
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
     the Free Software Foundation, either version 2 of the License, or
     (at your option) any later version.
 
     This program is distributed in the hope that it will be useful,
     but WITHOUT ANY WARRANTY; without even the implied warranty of
     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
     GNU General Public License for more details.
 
     You should have received a copy of the GNU General Public License
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
 #include "canvaswidget.h"
 #include "globals.h"
 #include "kbreakout_debug.h"
 #include "settings.h"
 
 #include <QGraphicsObject>
 #include <QAction>
 #include <QCursor>
 #include <QStandardPaths>
 #include <QQuickItem>
 
 #include <KgThemeProvider>
 
 CanvasWidget::CanvasWidget(QWidget *parent) :
     KgDeclarativeView(parent),
     m_provider(new KgThemeProvider)
 {
     m_provider->discoverThemes("appdata", QStringLiteral("themes"));
     m_provider->setDeclarativeEngine(QStringLiteral("themeProvider"), engine());
     QString path = QStandardPaths::locate(QStandardPaths::AppDataLocation, QStringLiteral("qml/main.qml"));
 
     qCDebug(KBREAKOUT_General) << "QtQuick QML file: " << path;
 
     setSource(QUrl::fromLocalFile(path));
 
     // forward signals from QML
     connect(rootObject(), SIGNAL(levelComplete()), this, SIGNAL(levelComplete()));
     connect(rootObject(), SIGNAL(gameEnded(int,int,int)), this, SIGNAL(gameEnded(int,int,int)));
     connect(rootObject(), SIGNAL(mousePressed()), this, SIGNAL(mousePressed()));
 
     // for handling mouse cursor
     connect(rootObject(), SIGNAL(pausedChanged()), this, SLOT(updateCursor()));
     connect(this, &CanvasWidget::gameEnded, this, &CanvasWidget::resetCursor);
 }
 
 CanvasWidget::~CanvasWidget()
 {
     delete m_provider;
 }
 
 void CanvasWidget::updateFireShortcut()
 {
     QAction *fireAction = qobject_cast<QAction *>(sender());
     QString shortcut = fireAction->shortcut().toString(QKeySequence::NativeText);
     rootObject()->setProperty("fireShortcut", shortcut);
 }
 
 void CanvasWidget::resizeEvent(QResizeEvent *event)
 {
     QQuickWidget::resizeEvent(event);
     QMetaObject::invokeMethod(rootObject(), "updateGeometry");
 }
 
 void CanvasWidget::newGame()
 {
     QMetaObject::invokeMethod(rootObject(), "reset");
 
     setCursor(QCursor(Qt::BlankCursor));
 }
 
-void CanvasWidget::showLine(QString line, int lineNumber)
+void CanvasWidget::showLine(const QString &line, int lineNumber)
 {
     QMetaObject::invokeMethod(rootObject(), "loadLine",
                               Q_ARG(QVariant, line),
                               Q_ARG(QVariant, lineNumber));
 }
 
-void CanvasWidget::putGift(QString gift, int times, QString pos)
+void CanvasWidget::putGift(const QString &gift, int times, const QString &pos)
 {
     QMetaObject::invokeMethod(rootObject(), "loadGift",
                               Q_ARG(QVariant, gift),
                               Q_ARG(QVariant, times),
                               Q_ARG(QVariant, pos));
 }
 
 void CanvasWidget::startGame()
 {
     QMetaObject::invokeMethod(rootObject(), "startGame");
 }
 
 void CanvasWidget::fire()
 {
     QMetaObject::invokeMethod(rootObject(), "fire");
 }
 
 void CanvasWidget::cheatSkipLevel()
 {
     QMetaObject::invokeMethod(rootObject(), "cheatSkipLevel");
 }
 
 void CanvasWidget::cheatAddLife()
 {
     QMetaObject::invokeMethod(rootObject(), "cheatAddLife");
 }
 
 void CanvasWidget::setGamePaused(bool paused)
 {
     QMetaObject::invokeMethod(rootObject(), "setGamePaused",
                               Q_ARG(QVariant, paused));
 }
 
 void CanvasWidget::updateBarDirection()
 {
     QMetaObject::invokeMethod(rootObject(), "updateBarDirection",
                               Q_ARG(QVariant, m_barDirection));
 }
 
 void CanvasWidget::resetCursor()
 {
     setCursor(QCursor(Qt::ArrowCursor));
 }
 
 void CanvasWidget::updateCursor()
 {
     bool paused = rootObject()->property("paused").toBool();
 
     if (paused) {
         resetCursor();
     } else {
         // FIXME: move the cursor to where the bar is
         resetMousePosition();
         QCursor newCursor(Qt::BlankCursor);
         newCursor.setPos(cursor().pos());
         setCursor(newCursor);
     }
 }
 
 void CanvasWidget::resetMousePosition()
 {
     // FIXME: the cursor's position is supposed to be reset,
     // just doesn't work!
     int barPosition = rootObject()->property("barCenter").toInt();
     QPoint p = mapToGlobal(QPoint(barPosition, 0));
     cursor().setPos(p.x(), cursor().pos().y());
 }
 
 void CanvasWidget::focusOutEvent(QFocusEvent *event)
 {
     emit focusLost();
     QQuickWidget::focusOutEvent(event);
 }
diff --git a/src/canvaswidget.h b/src/canvaswidget.h
index 9808551..b3a9f69 100644
--- a/src/canvaswidget.h
+++ b/src/canvaswidget.h
@@ -1,71 +1,71 @@
 /*
     Copyright 2012 Viranch Mehta <viranch.mehta@gmail.com>
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
     the Free Software Foundation, either version 2 of the License, or
     (at your option) any later version.
 
     This program is distributed in the hope that it will be useful,
     but WITHOUT ANY WARRANTY; without even the implied warranty of
     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
     GNU General Public License for more details.
 
     You should have received a copy of the GNU General Public License
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
 #ifndef CANVASWIDGET_H
 #define CANVASWIDGET_H
 
 #include <KgDeclarativeView>
 class KgThemeProvider;
 class CanvasWidget : public KgDeclarativeView
 {
     Q_OBJECT
 public:
     explicit CanvasWidget(QWidget *parent = nullptr);
     ~CanvasWidget() override;
     KgThemeProvider *getProvider()
     {
         return m_provider;
     }
 
 Q_SIGNALS:
     void levelComplete();
     void gameEnded(int score, int level, int elapsedTime);
     void focusLost();
     void mousePressed();
 
 public Q_SLOTS:
     void fire();
     void cheatSkipLevel();
     void cheatAddLife();
     void setGamePaused(bool paused);
     void updateFireShortcut();
 
 public Q_SLOTS:
     void newGame();
-    void showLine(QString line, int lineNumber);
-    void putGift(QString gift, int times, QString pos);
+    void showLine(const QString &line, int lineNumber);
+    void putGift(const QString &gift, int times, const QString &pos);
     void updateBarDirection();
     void startGame();
     void updateCursor();
     void resetCursor();
     void resetMousePosition();
 
 protected:
     void focusOutEvent(QFocusEvent *event) override;
     void resizeEvent(QResizeEvent *event) override;
 
 private:
     //used when moving the bar with the keys
     int m_barDirection;
 
     // used to track which direction keys are pressed between key events
     bool m_rightPressed;
     bool m_leftPressed;
     KgThemeProvider *m_provider;
 };
 
 #endif //CANVASWIDGET_H