Allow to draw square if shift is pressed

src/control/tools/RectangleHandler.cpp

@@ -25,16 +25,30 @@ void RectangleHandler::drawShape(Point& c, bool shiftDown)
 	{
 		stroke->addPoint(c);
 	}
-	else
+	else if (shiftDown)
 	{
+		// Draw square if shift is pressed
 		Point p = stroke->getPoint(0);
-		if (count > 3)
+
+		stroke->deletePointsFrom(1);
+
+		int size = MAX(ABS(c.x - p.x), ABS(c.y - p.y));
+
+		if (c.x - p.x < 0 || c.y - p.y < 0)
 		{
-			stroke->deletePoint(4);
-			stroke->deletePoint(3);
-			stroke->deletePoint(2);
-			stroke->deletePoint(1);
+			size = -size;
 		}
+
+		stroke->addPoint(Point(p.x, p.y + size));
+		stroke->addPoint(Point(p.x + size, p.y + size));
+		stroke->addPoint(Point(p.x + size, p.y));
+		stroke->addPoint(p);
+	}
+	else
+	{
+		Point p = stroke->getPoint(0);
+		stroke->deletePointsFrom(1);
+
 		stroke->addPoint(Point(c.x, p.y));
 		stroke->addPoint(c);
 		stroke->addPoint(Point(p.x, c.y));