Refactor code

src/main/java/ee/ut/dendroloj/CallTreeLayout.java

@@ -16,10 +16,6 @@
 
 class CallTreeLayout {
 
-    static {
-        GraphGUI.initProperties();
-    }
-
     public static final MetaTreeNode root = new MetaTreeNode();
     private static TreeNode currentNode = root;
 
@@ -29,12 +25,10 @@ class CallTreeLayout {
     public static final JSlider stepSlider;
 
     static {
-        stepSlider = new JSlider();
+        stepSlider = new JSlider(0, 0, 0);
         stepSlider.setEnabled(false);
         stepSlider.setPaintTicks(true);
         stepSlider.setMajorTickSpacing(1);
-        stepSlider.setMinimum(0);
-        stepSlider.setMaximum(0);
         stepSlider.addChangeListener(event -> {
             if (!internalSliderChange) {
                 setActiveStep(stepSlider.getValue());

src/main/java/ee/ut/dendroloj/Dendrologist.java

@@ -5,11 +5,15 @@
 import java.awt.Color;
 import java.util.Arrays;
 import java.util.List;
-import java.util.Objects;
 import java.util.function.Function;
 
 public final class Dendrologist {
 
+    static {
+        // Initialize global Swing and GraphStream properties as soon as possible
+        GraphGUI.initProperties();
+    }
+
     private static boolean awake = false;
 
     // Startup settings

src/main/java/ee/ut/dendroloj/GraphGUI.java

@@ -26,10 +26,8 @@ class GraphGUI {
     }
 
     /**
-     * Initializes global Swing and GraphStream properties.
-     * This will be called automatically when the GUI is initialized.
-     * You should call this manually before creating Swing objects
-     * if you create Swing objects before GUI is initialized.
+     * Initializes global Swing and GraphStream properties. This will be called automatically when the GUI is initialized.
+     * To avoid issues this should also be called manually before any initialization code that might create Swing objects.
      */
     public static void initProperties() {
         // The actual initialization happens inside the static block above