add 'slotIndex' ui slot property

src/frontend/hud.cpp

@@ -470,7 +470,9 @@ void Hud::showExchangeSlot() {
         SlotLayout(-1, glm::vec2(), false, false, nullptr, nullptr, nullptr)
     );
     exchangeSlot->setId("hud.exchange-slot");
-    exchangeSlot->bind(exchangeSlotInv->getId(), exchangeSlotInv->getSlot(0), &content);
+    exchangeSlot->bind(
+        exchangeSlotInv->getId(), exchangeSlotInv->getSlot(0), 0, &content
+    );
     exchangeSlot->setColor(glm::vec4());
     exchangeSlot->setInteractive(false);
     exchangeSlot->setZIndex(1);

src/graphics/ui/elements/InventoryView.cpp

@@ -452,10 +452,11 @@ const std::wstring& SlotView::getTooltip() const {
 }
 
 void SlotView::bind(
-    int64_t inventoryid, ItemStack& stack, const Content* content
+    int64_t inventoryid, ItemStack& stack, size_t index, const Content* content
 ) {
     this->inventoryId = inventoryid;
     bound = &stack;
+    this->index = index;
     this->content = content;
 }
 
@@ -471,6 +472,10 @@ int64_t SlotView::getInventoryId() const {
     return inventoryId;
 }
 
+size_t SlotView::getIndex() const {
+    return index;
+}
+
 InventoryView::InventoryView(GUI& gui) : Container(gui, glm::vec2()) {
     setColor(glm::vec4(0, 0, 0, 0.0f));
 }
@@ -514,9 +519,11 @@ void InventoryView::bind(
     this->inventory = inventory;
     this->content = content;
     for (auto slot : slots) {
+        const auto& layout = slot->getLayout();
         slot->bind(
             inventory->getId(),
-            inventory->getSlot(slot->getLayout().index),
+            inventory->getSlot(layout.index),
+            layout.index,
             content
         );
     }

src/graphics/ui/elements/InventoryView.hpp

@@ -63,6 +63,7 @@ namespace gui {
 
         int64_t inventoryId = 0;
         ItemStack* bound = nullptr;
+        size_t index = 0;
 
         void performLeftClick(ItemStack& stack, ItemStack& grabbed);
         void performRightClick(ItemStack& stack, ItemStack& grabbed);
@@ -100,12 +101,14 @@ namespace gui {
         void bind(
             int64_t inventoryid,
             ItemStack& stack,
+            size_t index,
             const Content* content
         );
 
         ItemStack& getStack();
         const SlotLayout& getLayout() const;
         int64_t getInventoryId() const;
+        size_t getIndex() const;
 
         static inline std::string EXCHANGE_SLOT_NAME = "exchange-slot";
     };

src/logic/scripting/lua/libs/libgui.cpp

@@ -215,6 +215,13 @@ static int p_get_inventory(UINode* node, lua::State* L) {
     return 0;
 }
 
+static int p_get_slot_index(UINode* node, lua::State* L) {
+    if (auto slot = dynamic_cast<SlotView*>(node)) {
+        return lua::pushinteger(L, slot->getIndex());
+    }
+    return 0;
+}
+
 static int p_get_reset(UINode* node, lua::State* L) {
     if (dynamic_cast<Menu*>(node)) {
         return lua::pushcfunction(L, l_menu_reset);
@@ -663,6 +670,7 @@ static int l_gui_getattr(lua::State* L) {
             {"reset", p_get_reset},
             {"paste", p_get_paste},
             {"inventory", p_get_inventory},
+            {"slotIndex", p_get_slot_index},
             {"focused", p_get_focused},
             {"cursor", p_get_cursor},
             {"data", p_get_data},