Change QString function parameters to const QString &

src/ui/linechart/ChartPlot.cc

@@ -70,7 +70,7 @@ QColor ChartPlot::getNextColor()
     return colors[nextColorIndex++];
 }
 
-QColor ChartPlot::getColorForCurve(QString id)
+QColor ChartPlot::getColorForCurve(const QString &id)
 {
     return curves.value(id)->pen().color();
 }

src/ui/linechart/ChartPlot.h

@@ -17,7 +17,7 @@ public:
     QColor getNextColor();
 
     /** @brief Get color for curve id */
-    QColor getColorForCurve(QString id);
+    QColor getColorForCurve(const QString &id);
 
     /** @brief Reset color map */
     void shuffleColors();

src/ui/linechart/IncrementalPlot.cc

@@ -155,7 +155,7 @@ void IncrementalPlot::showLegend(bool show)
  *
  * @param style Formatting string for line/data point style
  */
-void IncrementalPlot::setStyleText(QString style)
+void IncrementalPlot::setStyleText(const QString &style)
 {
     foreach (QwtPlotCurve* curve, curves) {
         // Style of datapoints
@@ -250,12 +250,12 @@ void IncrementalPlot::updateScale()
     zoomer->setZoomBase(true);
 }
 
-void IncrementalPlot::appendData(QString key, double x, double y)
+void IncrementalPlot::appendData(const QString &key, double x, double y)
 {
     appendData(key, &x, &y, 1);
 }
 
-void IncrementalPlot::appendData(QString key, double *x, double *y, int size)
+void IncrementalPlot::appendData(const QString &key, double *x, double *y, int size)
 {
     CurveData* data;
     QwtPlotCurve* curve;
@@ -349,7 +349,7 @@ void IncrementalPlot::appendData(QString key, double *x, double *y, int size)
 /**
  * @return Number of copied data points, 0 on failure
  */
-int IncrementalPlot::data(QString key, double* r_x, double* r_y, int maxSize)
+int IncrementalPlot::data(const QString &key, double* r_x, double* r_y, int maxSize)
 {
     int result = 0;
     if (d_data.contains(key)) {

src/ui/linechart/IncrementalPlot.h

@@ -84,14 +84,14 @@ public:
     bool gridEnabled();
 
     /** @brief Read out data from a curve */
-    int data(QString key, double* r_x, double* r_y, int maxSize);
+    int data(const QString &key, double* r_x, double* r_y, int maxSize);
 
 public slots:
     /** @brief Append one data point */
-    void appendData(QString key, double x, double y);
+    void appendData(const QString &key, double x, double y);
 
     /** @brief Append multiple data points */
-    void appendData(QString key, double* x, double* y, int size);
+    void appendData(const QString &key, double* x, double* y, int size);
 
     /** @brief Reset the plot scaling to the default value */
     void resetScaling();
@@ -109,7 +109,7 @@ public slots:
     void showGrid(bool show);
 
     /** @brief Set new plot style */
-    void setStyleText(QString style);
+    void setStyleText(const QString &style);
 
     /** @brief Set symmetric axis scaling mode */
     void setSymmetric(bool symmetric);