Extract drawing of info text into method

Extract the drawing of the info text into its own private method `drawInfoText`.

include/LfoGraph.h

@@ -49,6 +49,7 @@ class LfoGraph : public QWidget, public ModelView
 	void paintEvent(QPaintEvent* pe) override;
 
 private:
+	void drawInfoText(const EnvelopeAndLfoParameters&);
 	void toggleAmountModel();
 
 private:

src/gui/instrument/LfoGraph.cpp

@@ -150,7 +150,16 @@ void LfoGraph::paintEvent(QPaintEvent*)
 
 	p.drawPolyline(polyLine);
 
-	// Draw the info text
+	drawInfoText(*params);
+}
+
+void LfoGraph::drawInfoText(const EnvelopeAndLfoParameters& params)
+{
+	QPainter p(this);
+
+	const float lfoSpeed = params.getLfoSpeedModel().value();
+	const bool x100 = params.getX100Model().value();
+
 	const float hertz = 1. / (SECS_PER_LFO_OSCILLATION * lfoSpeed) * (x100 ? 100. : 1.);
 	const auto infoText = tr("%1 Hz").arg(hertz, 0, 'f', 3);