diff --git a/mibpov.js b/mibpov.js
index 3ea7dc9..7cc7ab0 100644
--- a/mibpov.js
+++ b/mibpov.js
@@ -873,8 +873,30 @@ function getSelectedBiomeIDAndElement() {
 	return [null, null];
 }
 
+// Show a message in the center of the given draw
+// context.
+function showDiagramMessage(context, text) {
+	context.textAlign = "center";
+	context.fillStyle = "black";
+	context.textBaseline = "middle";
+	if (voronoiCanvas.width < 300) {
+		context.font = "100% sans-serif";
+	} else if (voronoiCanvas.width < 450) {
+		context.font = "150% sans-serif";
+	} else {
+		context.font = "200% sans-serif";
+	}
+	context.fillText(text, voronoiCanvas.width/2, voronoiCanvas.height/2);
+	updateAltitudeText();
+}
+
+// Check if a diagram can be drawn on the draw context and
+// if not, draws a message and return false.
+// If everything is fine, return true.
 function checkDrawValid(context) {
 	if (!context) {
+		// We don't even have a valid draw context!
+		// Write an error message in the error message element
 		if (!voronoiCanvas.hidden) {
 			voronoiCanvas.hidden = true;
 			coordinateDisplay.hidden = true;
@@ -888,21 +910,6 @@ function checkDrawValid(context) {
 		return false;
 	}
 
-	let showDiagramMessage = function(context, text) {
-		context.textAlign = "center";
-		context.fillStyle = "black";
-		context.textBaseline = "middle";
-		if (voronoiCanvas.width < 300) {
-			context.font = "100% sans-serif";
-		} else if (voronoiCanvas.width < 450) {
-			context.font = "150% sans-serif";
-		} else {
-			context.font = "200% sans-serif";
-		}
-		context.fillText(text, voronoiCanvas.width/2, voronoiCanvas.height/2);
-		updateAltitudeText();
-	}
-
 	// Fail and render a special message if the value range is tiny
 	if ((limit_heat_max - limit_heat_min < 0.01) || (limit_humidity_max - limit_humidity_min < 0.01)) {
 		showDiagramMessage(context, "Value range is too small.");