fix p.6

res/content/base/scripts/hud.lua

@@ -5,6 +5,27 @@ function on_hud_open()
         local invid = hud.get_exchange_inventory()
         base_util.drop_from_slot(invid, 0, mode)
     end)
+
+    events.on("core:slot_middle_click", function(invid, slot)
+        if not player.is_infinite_items(hud.get_player()) then
+            return
+        end
+        local itemid = inventory.get(invid, slot)
+        local exc_invid = hud.get_exchange_inventory()
+        local exc_itemid = inventory.get(exc_invid, 0)
+        if itemid == 0 then
+            if exc_itemid ~= 0 then
+              local stack_size = item.stack_size(exc_itemid)
+              inventory.set(invid, slot, exc_itemid, stack_size)
+            end
+        else
+            if exc_itemid == 0 then
+              local stack_size = item.stack_size(itemid)
+              inventory.set(exc_invid, 0, itemid, stack_size)
+            end
+        end
+    end)
+
     input.add_callback("player.drop", function()
         if hud.is_paused() or hud.is_inventory_open() then
             return

src/graphics/ui/elements/InventoryView.cpp

@@ -501,16 +501,10 @@ void SlotView::performRightClick(ItemStack& stack, ItemStack& grabbed) {
 }
 
 void SlotView::performMiddleClick(ItemStack& stack, ItemStack& grabbed) {
-    auto indices = *content->getIndices();
-    if (!grabbed.isEmpty()) {
-        if (stack.isEmpty()) {
-            stack.set(grabbed);
-            stack.maximizeCount(indices);
-        }
-        return;
-    }
-    grabbed.set(stack);
-    grabbed.maximizeCount(indices);
+    scripting::on_slot_middle_click(
+        inventoryId,
+        layout.index
+    );
 }
 
 void SlotView::clicked(Mousecode button) {

src/logic/scripting/scripting.hpp

@@ -110,6 +110,8 @@ namespace scripting {
     void on_inventory_closed(const Player* player, const Inventory& inventory);
     void on_inventory_interact(int invid, int slot, int action, int mode);
 
+    void on_slot_middle_click(int invid, int slot);
+
     void on_player_tick(Player* player, int tps);
 
     /// @brief Called on RMB click with the item selected

src/logic/scripting/scripting_hud.cpp

@@ -110,6 +110,19 @@ void scripting::on_inventory_interact(int invid, int slot, int action, int mode)
     }
 }
 
+void scripting::on_slot_middle_click(int invid, int slot) {
+    auto L = lua::get_main_state();
+    lua::emit_event(
+        L,
+        "core:slot_middle_click",
+        [&](lua::State* L) {
+            lua::pushinteger(L, invid);
+            lua::pushinteger(L, slot);
+            return 2;
+        }
+    );
+}
+
 void scripting::load_hud_script(
     const scriptenv& senv,
     const std::string& packid,