tweaked stackable shulkerboxes for 1.17 fixes #989

src/main/java/carpet/CarpetSettings.java

@@ -192,7 +192,7 @@ public class CarpetSettings
 
     @Rule(
             desc = "Empty shulker boxes can stack to 64 when dropped on the ground",
-            extra = "To move them around between inventories, use shift click to move entire stacks",
+            extra = ".. or when manipulated inside the inventories",
             category = {SURVIVAL, FEATURE}
     )
     public static boolean stackableShulkerBoxes = false;

src/main/java/carpet/mixins/Slot_stackableSBoxesMixin.java

@@ -1,6 +1,7 @@
 package carpet.mixins;
 
 import carpet.CarpetSettings;
+import carpet.helpers.InventoryHelper;
 import net.minecraft.block.ShulkerBoxBlock;
 import net.minecraft.item.BlockItem;
 import net.minecraft.item.ItemStack;
@@ -17,7 +18,11 @@ public class Slot_stackableSBoxesMixin {
     ))
     private int getMaxCountForSboxes(Slot slot, ItemStack stack)
     {
-        if (CarpetSettings.stackableShulkerBoxes && stack.getItem() instanceof BlockItem && ((BlockItem)stack.getItem()).getBlock() instanceof ShulkerBoxBlock)
+        if (CarpetSettings.stackableShulkerBoxes &&
+                stack.getItem() instanceof BlockItem &&
+                ((BlockItem)stack.getItem()).getBlock() instanceof ShulkerBoxBlock &&
+                !InventoryHelper.shulkerBoxHasItems(stack)
+        )
         {
             return CarpetSettings.SHULKER_STACK_SIZE;
         }