Formspec: allow lists to change size and existence while the formspec is open (#9700)

Fixes #9640.

src/gui/guiFormSpecMenu.cpp

@@ -489,38 +489,10 @@ void GUIFormSpecMenu::parseList(parserData *data, const std::string &element)
 			start_i = stoi(startindex);
 
 		if (geom.X < 0 || geom.Y < 0 || start_i < 0) {
-			errorstream<< "Invalid list element: '" << element << "'"  << std::endl;
+			errorstream << "Invalid list element: '" << element << "'"  << std::endl;
 			return;
 		}
 
-		// check for the existence of inventory and list
-		Inventory *inv = m_invmgr->getInventory(loc);
-		if (!inv) {
-			warningstream << "GUIFormSpecMenu::parseList(): "
-					<< "The inventory location "
-					<< "\"" << loc.dump() << "\" doesn't exist"
-					<< std::endl;
-			return;
-		}
-		InventoryList *ilist = inv->getList(listname);
-		if (!ilist) {
-			warningstream << "GUIFormSpecMenu::parseList(): "
-					<< "The inventory list \"" << listname << "\" "
-					<< "@ \"" << loc.dump() << "\" doesn't exist"
-					<< std::endl;
-			return;
-		}
-
-		// trim geom if it is larger than the actual inventory size
-		s32 list_size = (s32)ilist->getSize();
-		if (list_size < geom.X * geom.Y + start_i) {
-			list_size -= MYMAX(start_i, 0);
-			geom.Y = list_size / geom.X;
-			geom.Y += list_size % geom.X > 0 ? 1 : 0;
-			if (geom.Y <= 1)
-				geom.X = list_size;
-		}
-
 		if (!data->explicit_size)
 			warningstream << "invalid use of list without a size[] element" << std::endl;
 

src/gui/guiInventoryList.cpp

@@ -47,7 +47,8 @@ GUIInventoryList::GUIInventoryList(gui::IGUIEnvironment *env,
 	m_fs_menu(fs_menu),
 	m_options(options),
 	m_font(font),
-	m_hovered_i(-1)
+	m_hovered_i(-1),
+	m_already_warned(false)
 {
 }
 
@@ -58,20 +59,27 @@ void GUIInventoryList::draw()
 
 	Inventory *inv = m_invmgr->getInventory(m_inventoryloc);
 	if (!inv) {
+		if (!m_already_warned) {
 			warningstream << "GUIInventoryList::draw(): "
 					<< "The inventory location "
-				<< "\"" << m_inventoryloc.dump() << "\" doesn't exist anymore"
+					<< "\"" << m_inventoryloc.dump() << "\" doesn't exist"
 					<< std::endl;
+			m_already_warned = true;
+		}
 		return;
 	}
 	InventoryList *ilist = inv->getList(m_listname);
 	if (!ilist) {
+		if (!m_already_warned) {
 			warningstream << "GUIInventoryList::draw(): "
 					<< "The inventory list \"" << m_listname << "\" @ \""
-				<< m_inventoryloc.dump() << "\" doesn't exist anymore"
+					<< m_inventoryloc.dump() << "\" doesn't exist"
 					<< std::endl;
+			m_already_warned = true;
+		}
 		return;
 	}
+	m_already_warned = false;
 
 	video::IVideoDriver *driver = Environment->getVideoDriver();
 	Client *client = m_fs_menu->getClient();
@@ -80,9 +88,11 @@ void GUIInventoryList::draw()
 	core::rect<s32> imgrect(0, 0, m_slot_size.X, m_slot_size.Y);
 	v2s32 base_pos = AbsoluteRect.UpperLeftCorner;
 
+	const s32 list_size = (s32)ilist->getSize();
+
 	for (s32 i = 0; i < m_geom.X * m_geom.Y; i++) {
 		s32 item_i = i + m_start_item_i;
-		if (item_i >= (s32)ilist->getSize())
+		if (item_i >= list_size)
 			break;
 
 		v2s32 p((i % m_geom.X) * m_slot_spacing.X,
@@ -192,10 +202,19 @@ bool GUIInventoryList::OnEvent(const SEvent &event)
 
 s32 GUIInventoryList::getItemIndexAtPos(v2s32 p) const
 {
+	// no item if no gui element at pointer
 	if (!IsVisible || AbsoluteClippingRect.getArea() <= 0 ||
 			!AbsoluteClippingRect.isPointInside(p))
 		return -1;
 
+	// there can not be an item if the inventory or the inventorylist does not exist
+	Inventory *inv = m_invmgr->getInventory(m_inventoryloc);
+	if (!inv)
+		return -1;
+	InventoryList *ilist = inv->getList(m_listname);
+	if (!ilist)
+		return -1;
+
 	core::rect<s32> imgrect(0, 0, m_slot_size.X, m_slot_size.Y);
 	v2s32 base_pos = AbsoluteRect.UpperLeftCorner;
 
@@ -210,7 +229,8 @@ s32 GUIInventoryList::getItemIndexAtPos(v2s32 p) const
 
 	rect.clipAgainst(AbsoluteClippingRect);
 
-	if (rect.getArea() > 0 && rect.isPointInside(p))
+	if (rect.getArea() > 0 && rect.isPointInside(p) &&
+			i + m_start_item_i < (s32)ilist->getSize())
 		return i + m_start_item_i;
 
 	return -1;

src/gui/guiInventoryList.h

@@ -107,7 +107,7 @@ private:
 	const InventoryLocation m_inventoryloc;
 	const std::string m_listname;
 
-	// specifies the width and height of the inventorylist in itemslots
+	// the specified width and height of the shown inventorylist in itemslots
 	const v2s32 m_geom;
 	// the first item's index in inventory
 	const s32 m_start_item_i;
@@ -127,4 +127,7 @@ private:
 
 	// the index of the hovered item; -1 if no item is hovered
 	s32 m_hovered_i;
+
+	// we do not want to write a warning on every draw
+	bool m_already_warned;
 };