i was dealing with wrong function xD

src/net/torvald/terrarum/UIItemInventoryCatBar.kt

@@ -23,8 +23,8 @@ class UIItemInventoryCatBar(
         initialY: Int,
         uiInternalWidth: Int,
         override val width: Int,
-        val transitionReqFun: (Int) -> Unit,
-        val showSideButtons: Boolean
+        val showSideButtons: Boolean = false,
+        val panelTransitionReqFun: (Int) -> Unit = {} // for side buttons; for the selection change, override selectionChangeListener
 ) : UIItem(parentUI, initialX, initialY) {
 
     companion object {
@@ -242,7 +242,7 @@ class UIItemInventoryCatBar(
 
             if (transitionFired) {
                 transitionFired = false
-                transitionReqFun(selectedPanel)
+                panelTransitionReqFun(selectedPanel)
             }
         }
     }

src/net/torvald/terrarum/modulebasegame/gameactors/FixtureStorageChest.kt

@@ -76,9 +76,9 @@ internal object UIStorageChest : UICanvas(), HasInventory {
                 50,
                 500,
                 500,
-                { itemList.rebuild(catBar.catIconsMeaning[catBar.selectedIcon]) },
                 false
         )
+        catBar.selectionChangeListener = { old, new -> itemListUpdate() }
         itemList = UIItemInventoryItemGrid(
                 this,
                 catBar,
@@ -86,7 +86,7 @@ internal object UIStorageChest : UICanvas(), HasInventory {
                 100,
                 100,
                 4, 5,
-                drawScrollOnRightside = true,
+                drawScrollOnRightside = false,
                 drawWallet = true,
                 keyDownFun = { _,_ -> Unit },
                 touchDownFun = { _,_,_,_,_ -> itemListUpdate() }

src/net/torvald/terrarum/modulebasegame/ui/UIInventoryFull.kt

@@ -91,8 +91,8 @@ class UIInventoryFull(
             42 + (AppLoader.screenH - internalHeight) / 2,
             internalWidth,
             catBarWidth,
-            { i -> requestTransition(i) },
-            true
+            true,
+            { i -> requestTransition(i) }
     )