Use const references where possible

Good practice and a minor performance improvement.

lib/HistorySearch.cpp

@@ -24,7 +24,7 @@
 #include "Emulation.h"
 #include "HistorySearch.h"
 
-HistorySearch::HistorySearch(EmulationPtr emulation, QRegExp regExp,
+HistorySearch::HistorySearch(EmulationPtr emulation, const QRegExp& regExp,
         bool forwards, int startColumn, int startLine,
         QObject* parent) :
 QObject(parent),

lib/HistorySearch.h

@@ -38,7 +38,7 @@ class HistorySearch : public QObject
     Q_OBJECT
 
 public:
-    explicit HistorySearch(EmulationPtr emulation, QRegExp regExp, bool forwards,
+    explicit HistorySearch(EmulationPtr emulation, const QRegExp& regExp, bool forwards,
                            int startColumn, int startLine, QObject* parent);
 
     ~HistorySearch() override;

lib/TerminalDisplay.cpp

@@ -711,7 +711,7 @@ void TerminalDisplay::setOpacity(qreal opacity)
     _blendColor = color.rgba();
 }
 
-void TerminalDisplay::setBackgroundImage(QString backgroundImage)
+void TerminalDisplay::setBackgroundImage(const QString& backgroundImage)
 {
     if (!backgroundImage.isEmpty())
     {

lib/TerminalDisplay.h

@@ -104,7 +104,7 @@ public:
     void setOpacity(qreal opacity);
 
     /** Sets the background image of the terminal display. */
-    void setBackgroundImage(QString backgroundImage);
+    void setBackgroundImage(const QString& backgroundImage);
 
     /**
      * Specifies whether the terminal display has a vertical scroll bar, and if so whether it

lib/qtermwidget.cpp

@@ -369,7 +369,7 @@ void QTermWidget::setTerminalOpacity(qreal level)
     m_impl->m_terminalDisplay->setOpacity(level);
 }
 
-void QTermWidget::setTerminalBackgroundImage(QString backgroundImage)
+void QTermWidget::setTerminalBackgroundImage(const QString& backgroundImage)
 {
     m_impl->m_terminalDisplay->setBackgroundImage(backgroundImage);
 }

lib/qtermwidget.h

@@ -87,7 +87,7 @@ public:
     void setTerminalFont(const QFont & font);
     QFont getTerminalFont();
     void setTerminalOpacity(qreal level);
-    void setTerminalBackgroundImage(QString backgroundImage);
+    void setTerminalBackgroundImage(const QString& backgroundImage);
 
     //environment
     void setEnvironment(const QStringList & environment);