diff --git a/src/Chart.vala b/src/Chart.vala
index 905a3c3..dcae56a 100644
--- a/src/Chart.vala
+++ b/src/Chart.vala
@@ -46,9 +46,11 @@ namespace Gtk.CairoChart {
 				cur_y_max = cur_y_min;
 		}
 
-		public virtual bool draw () {
-
+		public virtual void clear () {
 			draw_background ();
+		}
+
+		public virtual bool draw () {
 
 			cur_x_min = cur_y_min = 0.0;
 			cur_x_max = width;
diff --git a/test/ChartTest.vala b/test/ChartTest.vala
index 68a6378..deb3872 100644
--- a/test/ChartTest.vala
+++ b/test/ChartTest.vala
@@ -340,11 +340,14 @@ int main (string[] args) {
 	double mov_x0 = 0, mov_y0 = 0;
 
 	da.draw.connect((context) => {
-	    // user's pre draw operations here...
-
 		chart.context = context;
 		chart.width = da.get_allocated_width();
 		chart.height = da.get_allocated_height();
+		chart.clear();
+
+		// user's pre draw operations here...
+		// ...
+
 		/*var ret = */chart.draw();
 
 	    // user's post draw operations here...