Only re-create path list if path actually changed in window tick

Author: NichtStudioCode

invui/src/main/java/xyz/xenondevs/invui/gui/SlotElement.java

@@ -249,6 +249,25 @@ public ItemStack getItemStack(Player player) {
             return Collections.unmodifiableList(elements);
         }
 
+        /**
+         * Follows {@link #getHoldingElement()} until a non-{@link GuiLink} is reached and compares the path
+         * to the given list as returned by {@link #traverse()}.
+         *
+         * @return {@code true} if the path matches the given list, {@code false} otherwise.
+         */
+        public boolean checkTraverse(List<SlotElement> other) {
+            int i = 0;
+            SlotElement current = this;
+            while (current instanceof GuiLink(Gui g, int s)) {
+                if (i >= other.size() || !current.equals(other.get(i)))
+                    return false;
+                current = g.getSlotElement(s);
+                i++;
+            }
+            return (i == other.size() && current == null) 
+                   || (i == other.size() - 1 && other.getLast().equals(current));
+        }
+        
         @Override
         public void addObserver(Observer who, int how) {
             gui.addObserver(who, slot, how);

invui/src/main/java/xyz/xenondevs/invui/window/AbstractWindow.java

@@ -109,19 +109,20 @@ protected void update(int slot) {
         if (root == null)
             return;
 
-        List<SlotElement> newPath = root.traverse();
-        List<SlotElement> oldPath = elementsDisplayed.get(slot);
+        List<SlotElement> path = elementsDisplayed.get(slot);
 
         // if path has changed, viewers need to be updated
-        if (!newPath.equals(oldPath)) {
-            unregisterAsViewer(slot, oldPath);
-            registerAsViewer(slot, newPath);
-            elementsDisplayed.set(slot, newPath);
+        if (!root.checkTraverse(path)) {
+            unregisterAsViewer(slot, path);
+            path = root.traverse();
+            
+            registerAsViewer(slot, path);
+            elementsDisplayed.set(slot, path);
         }
 
         // create and place item stack in inventory
         ItemStack itemStack;
-        SlotElement lastElement = newPath.getLast();
+        SlotElement lastElement = path.getLast();
         if (!(lastElement instanceof SlotElement.GuiLink)) {
             itemStack = lastElement.getItemStack(getViewer());
             if (itemStack != null && lastElement instanceof SlotElement.Item) {
@@ -131,7 +132,7 @@ protected void update(int slot) {
             }
         } else { // there is no holding element
             // background by gui
-            itemStack = newPath.reversed().stream()
+            itemStack = path.reversed().stream()
                 .filter(e -> e instanceof SlotElement.GuiLink)
                 .map(e -> ((SlotElement.GuiLink) e).gui().getBackground())
                 .filter(Objects::nonNull)