diff --git a/src/plot.h b/src/plot.h
--- a/src/plot.h
+++ b/src/plot.h
@@ -27,6 +27,7 @@
 #include <qwt_plot_grid.h>
 #include <qwt_plot_shapeitem.h>
 #include <qwt_plot_legenditem.h>
+#include <qwt_plot_textlabel.h>
 
 #include "zoomer.h"
 #include "scalezoomer.h"
@@ -50,6 +51,7 @@ private:
     QwtPlotGrid grid;
     PlotSnapshotOverlay* snapshotOverlay;
     QwtPlotLegendItem legend;
+    QwtPlotTextLabel demoIndicator;
 
     void resetAxes();
 
@@ -57,6 +59,7 @@ public slots:
     void showGrid(bool show = true);
     void showMinorGrid(bool show = true);
     void showLegend(bool show = true);
+    void showDemoIndicator(bool show = true);
     void unzoom();
     void darkBackground(bool enabled = true);
     void setAxis(bool autoScaled, double yMin = 0, double yMax = 1);