7 files changed, 242 insertions, 182 deletions

diff --git a/src/Bindings/LuaState.cpp b/src/Bindings/LuaState.cpp
index 91a9ef4d6..98507e96c 100644
--- a/src/Bindings/LuaState.cpp
+++ b/src/Bindings/LuaState.cpp
@@ -180,6 +180,25 @@ bool cLuaState::cCallback::IsValid(void)
 
 
 
+bool cLuaState::cCallback::IsSameLuaState(cLuaState & a_LuaState)
+{
+	cCSLock lock(m_CS);
+	if (!m_Ref.IsValid())
+	{
+		return false;
+	}
+	auto canonState = a_LuaState.QueryCanonLuaState();
+	if (canonState == nullptr)
+	{
+		return false;
+	}
+	return (m_Ref.GetLuaState() == static_cast<lua_State *>(*canonState));
+}
+
+
+
+
+
 void cLuaState::cCallback::Invalidate(void)
 {
 	cCSLock Lock(m_CS);
@@ -919,6 +938,18 @@ void cLuaState::Push(std::chrono::milliseconds a_Value)
 
 
 
+void cLuaState::Pop(int a_NumValuesToPop)
+{
+	ASSERT(IsValid());
+
+	lua_pop(m_LuaState, a_NumValuesToPop);
+	m_NumCurrentFunctionArgs -= a_NumValuesToPop;
+}
+
+
+
+
+
 bool cLuaState::GetStackValue(int a_StackPos, AString & a_Value)
 {
 	size_t len = 0;
@@ -1647,7 +1678,7 @@ int cLuaState::CopyStackFrom(cLuaState & a_SrcLuaState, int a_SrcStart, int a_Sr
 				LOGWARNING("%s: Unsupported value: '%s' at stack position %d. Can only copy numbers, strings, bools and classes!",
 					__FUNCTION__, lua_typename(a_SrcLuaState, t), i
 				);
-				a_SrcLuaState.LogStack("Stack where copying failed:");
+				a_SrcLuaState.LogStackValues("Stack where copying failed:");
 				lua_pop(m_LuaState, i - a_SrcStart);
 				return -1;
 			}
@@ -1674,16 +1705,16 @@ void cLuaState::ToString(int a_StackPos, AString & a_String)
 
 
 
-void cLuaState::LogStack(const char * a_Header)
+void cLuaState::LogStackValues(const char * a_Header)
 {
-	LogStack(m_LuaState, a_Header);
+	LogStackValues(m_LuaState, a_Header);
 }
 
 
 
 
 
-void cLuaState::LogStack(lua_State * a_LuaState, const char * a_Header)
+void cLuaState::LogStackValues(lua_State * a_LuaState, const char * a_Header)
 {
 	// Format string consisting only of %s is used to appease the compiler
 	LOG("%s", (a_Header != nullptr) ? a_Header : "Lua C API Stack contents:");
@@ -1708,6 +1739,21 @@ void cLuaState::LogStack(lua_State * a_LuaState, const char * a_Header)
 
 
 
+cLuaState * cLuaState::QueryCanonLuaState(void)
+{
+	// Get the CanonLuaState global from Lua:
+	auto cb = WalkToNamedGlobal(g_CanonLuaStateGlobalName);
+	if (!cb.IsValid())
+	{
+		return nullptr;
+	}
+	return reinterpret_cast<cLuaState *>(lua_touserdata(m_LuaState, -1));
+}
+
+
+
+
+
 int cLuaState::ReportFnCallErrors(lua_State * a_LuaState)
 {
 	LOGWARNING("LUA: %s", lua_tostring(a_LuaState, -1));
@@ -1745,17 +1791,16 @@ int cLuaState::BreakIntoDebugger(lua_State * a_LuaState)
 void cLuaState::TrackCallback(cCallback & a_Callback)
 {
 	// Get the CanonLuaState global from Lua:
-	auto cb = WalkToNamedGlobal(g_CanonLuaStateGlobalName);
-	if (!cb.IsValid())
+	auto canonState = QueryCanonLuaState();
+	if (canonState == nullptr)
 	{
 		LOGWARNING("%s: Lua state %p has invalid CanonLuaState!", __FUNCTION__, reinterpret_cast<void *>(m_LuaState));
 		return;
 	}
-	auto & canonState = *reinterpret_cast<cLuaState *>(lua_touserdata(m_LuaState, -1));
 
 	// Add the callback:
-	cCSLock Lock(canonState.m_CSTrackedCallbacks);
-	canonState.m_TrackedCallbacks.push_back(&a_Callback);
+	cCSLock Lock(canonState->m_CSTrackedCallbacks);
+	canonState->m_TrackedCallbacks.push_back(&a_Callback);
 }
 
 
@@ -1765,17 +1810,16 @@ void cLuaState::TrackCallback(cCallback & a_Callback)
 void cLuaState::UntrackCallback(cCallback & a_Callback)
 {
 	// Get the CanonLuaState global from Lua:
-	auto cb = WalkToNamedGlobal(g_CanonLuaStateGlobalName);
-	if (!cb.IsValid())
+	auto canonState = QueryCanonLuaState();
+	if (canonState == nullptr)
 	{
 		LOGWARNING("%s: Lua state %p has invalid CanonLuaState!", __FUNCTION__, reinterpret_cast<void *>(m_LuaState));
 		return;
 	}
-	auto & canonState = *reinterpret_cast<cLuaState *>(lua_touserdata(m_LuaState, -1));
 
 	// Remove the callback:
-	cCSLock Lock(canonState.m_CSTrackedCallbacks);
-	auto & trackedCallbacks = canonState.m_TrackedCallbacks;
+	cCSLock Lock(canonState->m_CSTrackedCallbacks);
+	auto & trackedCallbacks = canonState->m_TrackedCallbacks;
 	trackedCallbacks.erase(std::remove_if(trackedCallbacks.begin(), trackedCallbacks.end(),
 		[&a_Callback](cCallback * a_StoredCallback)
 		{
diff --git a/src/Bindings/LuaState.h b/src/Bindings/LuaState.h
index 60a960ccc..0509b09ed 100644
--- a/src/Bindings/LuaState.h
+++ b/src/Bindings/LuaState.h
@@ -83,6 +83,15 @@ public:
 		/** Returns the Lua state associated with the value. */
 		lua_State * GetLuaState(void) { return m_LuaState; }
 
+		/** Creates a Lua reference to the specified object instance in the specified Lua state.
+		This is useful to make anti-GC references for objects that were created by Lua and need to stay alive longer than Lua GC would normally guarantee. */
+		template <typename T> void CreateFromObject(cLuaState & a_LuaState, T && a_Object)
+		{
+			a_LuaState.Push(std::forward<T>(a_Object));
+			RefStack(a_LuaState, -1);
+			a_LuaState.Pop();
+		}
+
 	protected:
 		lua_State * m_LuaState;
 		int m_Ref;
@@ -158,6 +167,10 @@ public:
 		/** Returns true if the contained callback is valid. */
 		bool IsValid(void);
 
+		/** Returns true if the callback resides in the specified Lua state.
+		Internally, compares the callback's canon Lua state. */
+		bool IsSameLuaState(cLuaState & a_LuaState);
+
 	protected:
 		friend class cLuaState;
 
@@ -330,6 +343,9 @@ public:
 	void Push(const UInt32 a_Value);
 	void Push(std::chrono::milliseconds a_time);
 
+	/** Pops the specified number of values off the top of the Lua stack. */
+	void Pop(int a_NumValuesToPop = 1);
+
 	// GetStackValue() retrieves the value at a_StackPos, if it is a valid type. If not, a_Value is unchanged.
 	// Returns whether value was changed
 	// Enum values are checked for their allowed values and fail if the value is not assigned.
@@ -499,10 +515,14 @@ public:
 	void ToString(int a_StackPos, AString & a_String);
 
 	/** Logs all the elements' types on the API stack, with an optional header for the listing. */
-	void LogStack(const char * a_Header = nullptr);
+	void LogStackValues(const char * a_Header = nullptr);
 
 	/** Logs all the elements' types on the API stack, with an optional header for the listing. */
-	static void LogStack(lua_State * a_LuaState, const char * a_Header = nullptr);
+	static void LogStackValues(lua_State * a_LuaState, const char * a_Header = nullptr);
+
+	/** Returns the canon Lua state (the primary cLuaState instance that was used to create, rather than attach, the lua_State structure).
+	Returns nullptr if the canon Lua state cannot be queried. */
+	cLuaState * QueryCanonLuaState(void);
 
 protected:
 
diff --git a/src/Bindings/LuaWindow.cpp b/src/Bindings/LuaWindow.cpp
index 706397a27..bf3f7cfde 100644
--- a/src/Bindings/LuaWindow.cpp
+++ b/src/Bindings/LuaWindow.cpp
@@ -15,14 +15,13 @@
 ////////////////////////////////////////////////////////////////////////////////
 // cLuaWindow:
 
-cLuaWindow::cLuaWindow(cWindow::WindowType a_WindowType, int a_SlotsX, int a_SlotsY, const AString & a_Title) :
-	super(a_WindowType, a_Title),
+cLuaWindow::cLuaWindow(cLuaState & a_LuaState, cWindow::WindowType a_WindowType, int a_SlotsX, int a_SlotsY, const AString & a_Title) :
+	Super(a_WindowType, a_Title),
 	m_Contents(a_SlotsX, a_SlotsY),
-	m_Plugin(nullptr),
-	m_LuaRef(LUA_REFNIL),
-	m_OnClosingFnRef(LUA_REFNIL),
-	m_OnSlotChangedFnRef(LUA_REFNIL)
+	m_LuaState(a_LuaState.QueryCanonLuaState())
 {
+	ASSERT(m_LuaState != nullptr);  // We must have a valid Lua state; this assert fails only if there was no Canon Lua state
+
 	m_Contents.AddListener(*this);
 	m_SlotAreas.push_back(new cSlotAreaItemGrid(m_Contents, *this));
 
@@ -67,62 +66,42 @@ cLuaWindow::~cLuaWindow()
 
 
 
-void cLuaWindow::SetLuaRef(cPluginLua * a_Plugin, int a_LuaRef)
+void cLuaWindow::SetOnClosing(cLuaState::cCallbackPtr a_OnClosing)
 {
-	// Either m_Plugin is not set or equal to the passed plugin; only one plugin can use one cLuaWindow object
-	ASSERT((m_Plugin == nullptr) || (m_Plugin == a_Plugin));
-	ASSERT(m_LuaRef == LUA_REFNIL);
-	m_Plugin = a_Plugin;
-	m_LuaRef = a_LuaRef;
-}
-
-
-
+	// Only one Lua state can be a cLuaWindow object callback:
+	ASSERT(a_OnClosing->IsSameLuaState(*m_LuaState));
 
-
-bool cLuaWindow::IsLuaReferenced(void) const
-{
-	return ((m_Plugin != nullptr) && (m_LuaRef != LUA_REFNIL));
+	// Store the new reference, releasing the old one if appropriate:
+	m_OnClosing = a_OnClosing;
 }
 
 
 
 
 
-void cLuaWindow::SetOnClosing(cPluginLua * a_Plugin, int a_FnRef)
+void cLuaWindow::SetOnSlotChanged(cLuaState::cCallbackPtr a_OnSlotChanged)
 {
-	// Either m_Plugin is not set or equal to the passed plugin; only one plugin can use one cLuaWindow object
-	ASSERT((m_Plugin == nullptr) || (m_Plugin == a_Plugin));
+	// Only one Lua state can be a cLuaWindow object callback:
+	ASSERT(a_OnSlotChanged->IsSameLuaState(*m_LuaState));
 
-	// If there already was a function, unreference it first
-	if (m_OnClosingFnRef != LUA_REFNIL)
-	{
-		m_Plugin->Unreference(m_OnClosingFnRef);
-	}
-
-	// Store the new reference
-	m_Plugin = a_Plugin;
-	m_OnClosingFnRef = a_FnRef;
+	// Store the new reference, releasing the old one if appropriate:
+	m_OnSlotChanged = a_OnSlotChanged;
 }
 
 
 
 
 
-void cLuaWindow::SetOnSlotChanged(cPluginLua * a_Plugin, int a_FnRef)
+void cLuaWindow::OpenedByPlayer(cPlayer & a_Player)
 {
-	// Either m_Plugin is not set or equal to the passed plugin; only one plugin can use one cLuaWindow object
-	ASSERT((m_Plugin == nullptr) || (m_Plugin == a_Plugin));
-
-	// If there already was a function, unreference it first
-	if (m_OnSlotChangedFnRef != LUA_REFNIL)
+	// If the first player is opening the window, create a Lua Reference to the window object so that Lua will not GC it until the last player closes the window:
+	if (m_PlayerCount == 0)
 	{
-		m_Plugin->Unreference(m_OnSlotChangedFnRef);
+		m_LuaRef.CreateFromObject(*m_LuaState, this);
 	}
 
-	// Store the new reference
-	m_Plugin = a_Plugin;
-	m_OnSlotChangedFnRef = a_FnRef;
+	++m_PlayerCount;
+	Super::OpenedByPlayer(a_Player);
 }
 
 
@@ -132,17 +111,27 @@ void cLuaWindow::SetOnSlotChanged(cPluginLua * a_Plugin, int a_FnRef)
 bool cLuaWindow::ClosedByPlayer(cPlayer & a_Player, bool a_CanRefuse)
 {
 	// First notify the plugin through the registered callback:
-	if (m_OnClosingFnRef != LUA_REFNIL)
+	if (m_OnClosing != nullptr)
 	{
-		ASSERT(m_Plugin != nullptr);
-		if (m_Plugin->CallbackWindowClosing(m_OnClosingFnRef, *this, a_Player, a_CanRefuse))
+		bool res;
+		if (
+			m_OnClosing->Call(this, &a_Player, a_CanRefuse, cLuaState::Return, res) &&  // The callback succeeded
+			res                                                                        // The callback says not to close the window
+		)
 		{
 			// The callback disagrees (the higher levels check the CanRefuse flag compliance)
 			return false;
 		}
 	}
 
-	return super::ClosedByPlayer(a_Player, a_CanRefuse);
+	// If the last player has closed the window, release the Lua reference, so that Lua may GC the object:
+	--m_PlayerCount;
+	if (m_PlayerCount == 0)
+	{
+		m_LuaRef.UnRef();
+	}
+
+	return Super::ClosedByPlayer(a_Player, a_CanRefuse);
 }
 
 
@@ -151,13 +140,7 @@ bool cLuaWindow::ClosedByPlayer(cPlayer & a_Player, bool a_CanRefuse)
 
 void cLuaWindow::Destroy(void)
 {
-	super::Destroy();
-
-	if ((m_LuaRef != LUA_REFNIL) && (m_Plugin != nullptr))
-	{
-		// The object is referenced by Lua, un-reference it
-		m_Plugin->Unreference(m_LuaRef);
-	}
+	Super::Destroy();
 
 	// Lua will take care of this object, it will garbage-collect it, so we must not delete it!
 	m_IsDestroyed = false;
@@ -178,7 +161,7 @@ void cLuaWindow::DistributeStack(cItem & a_ItemStack, int a_Slot, cPlayer & a_Pl
 		}
 	}
 
-	super::DistributeStackToAreas(a_ItemStack, a_Player, Areas, a_ShouldApply, false);
+	Super::DistributeStackToAreas(a_ItemStack, a_Player, Areas, a_ShouldApply, false);
 }
 
 
@@ -194,9 +177,9 @@ void cLuaWindow::OnSlotChanged(cItemGrid * a_ItemGrid, int a_SlotNum)
 	}
 
 	// If an OnSlotChanged callback has been registered, call it:
-	if (m_OnSlotChangedFnRef != LUA_REFNIL)
+	if (m_OnSlotChanged != nullptr)
 	{
-		m_Plugin->CallbackWindowSlotChanged(m_OnSlotChangedFnRef, *this, a_SlotNum);
+		m_OnSlotChanged->Call(this, a_SlotNum);
 	}
 }
 
diff --git a/src/Bindings/LuaWindow.h b/src/Bindings/LuaWindow.h
index f292a5154..2a16d91ed 100644
--- a/src/Bindings/LuaWindow.h
+++ b/src/Bindings/LuaWindow.h
@@ -9,6 +9,8 @@
 
 #pragma once
 
+#include <atomic>
+#include "LuaState.h"
 #include "../UI/Window.h"
 #include "../ItemGrid.h"
 
@@ -16,35 +18,30 @@
 
 
 
-// fwd: PluginLua.h
-class cPluginLua;
-
-
-
-
-
 /** A window that has been created by a Lua plugin and is handled entirely by that plugin
 This object needs extra care with its lifetime management:
 - It is created by Lua, so Lua expects to garbage-collect it later
-- normal cWindow objects are deleted in their ClosedByPlayer() function if the last player closes them
-To overcome this, this object overloads the Destroy functions, which doesn't let the ClosedByPlayer()
-delete the window, but rather leaves it dangling, with only Lua having the reference to it.
-Additionally, to forbid Lua from deleting this object while it is used by players, the manual bindings for
-cPlayer:OpenWindow check if the window is of this class, and if so, make a global Lua reference for this object.
-This reference needs to be unreferenced in the Destroy() function. */
+- Normal cWindow objects are deleted in their ClosedByPlayer() function if the last player closes them
+	To overcome this, this object overloads the Destroy functions, which doesn't let the ClosedByPlayer()
+	delete the window, but rather leaves it dangling, with only Lua having the reference to it.
+- Lua could GC the window while a player is still using it
+	The object creates a Lua reference to itself when opened by a player and
+	removes the reference when the last player closes the window.
+*/
 // tolua_begin
 class cLuaWindow :
 	public cWindow
 	// tolua_end
 	, public cItemGrid::cListener
-	// tolua_begin
-{
-	typedef cWindow super;
+{  // tolua_export
+	typedef cWindow Super;
 
 public:
-	/** Create a window of the specified type, with a slot grid of a_SlotsX * a_SlotsY size */
-	cLuaWindow(cWindow::WindowType a_WindowType, int a_SlotsX, int a_SlotsY, const AString & a_Title);
+	/** Create a window of the specified type, with a slot grid of a_SlotsX * a_SlotsY size.
+	Exported in ManualBindings.cpp */
+	cLuaWindow(cLuaState & a_LuaState, cWindow::WindowType a_WindowType, int a_SlotsX, int a_SlotsY, const AString & a_Title);
 
+	// tolua_begin
 	virtual ~cLuaWindow();
 
 	/** Returns the internal representation of the contents that are manipulated by Lua */
@@ -52,36 +49,37 @@ public:
 
 	// tolua_end
 
-	/** Sets the plugin reference and the internal Lua object reference index
-	used for preventing Lua's GC to collect this class while the window is open. */
-	void SetLuaRef(cPluginLua * a_Plugin, int a_LuaRef);
-
-	/** Returns true if SetLuaRef() has been called */
-	bool IsLuaReferenced(void) const;
-
-	/** Sets the callback function (Lua reference) to call when the window is about to close */
-	void SetOnClosing(cPluginLua * a_Plugin, int a_FnRef);
+	/** Sets the Lua callback function to call when the window is about to close */
+	void SetOnClosing(cLuaState::cCallbackPtr a_OnClosing);
 
-	/** Sets the callback function (Lua reference) to call when a slot is changed */
-	void SetOnSlotChanged(cPluginLua * a_Plugin, int a_FnRef);
+	/** Sets the Lua callback function to call when a slot is changed */
+	void SetOnSlotChanged(cLuaState::cCallbackPtr a_OnSlotChanged);
 
 protected:
+
 	/** Contents of the non-inventory part */
 	cItemGrid m_Contents;
 
-	/** The plugin that has opened the window and owns the m_LuaRef */
-	cPluginLua * m_Plugin;
+	/** The Lua state that has opened the window and owns the m_LuaRef */
+	cLuaState * m_LuaState;
+
+	/** The Lua callback to call when the window is closing for any player */
+	cLuaState::cCallbackPtr m_OnClosing;
+
+	/** The Lua callback to call when a slot has changed */
+	cLuaState::cCallbackPtr m_OnSlotChanged;
 
-	/** The Lua object reference, used for keeping the object alive as long as any player has the window open */
-	int m_LuaRef;
+	/** Number of players that are currently using the window.
+	Used to manager the m_LuaRef lifetime. */
+	std::atomic<int> m_PlayerCount;
 
-	/** The Lua reference for the callback to call when the window is closing for any player */
-	int m_OnClosingFnRef;
+	/** Reference to self, to keep Lua from GCing the object while a player is still using it.
+	Created when the first player opens the window, destroyed when the last player closes the window. */
+	cLuaState::cRef m_LuaRef;
 
-	/** The Lua reference for the callback to call when a slot has changed */
-	int m_OnSlotChangedFnRef;
 
 	// cWindow overrides:
+	virtual void OpenedByPlayer(cPlayer & a_Player) override;
 	virtual bool ClosedByPlayer(cPlayer & a_Player, bool a_CanRefuse) override;
 	virtual void Destroy(void) override;
 	virtual void DistributeStack(cItem & a_ItemStack, int a_Slot, cPlayer & a_Player, cSlotArea * a_ClickedArea, bool a_ShouldApply) override;
diff --git a/src/Bindings/ManualBindings.cpp b/src/Bindings/ManualBindings.cpp
index f3526d5a4..f041ef524 100644
--- a/src/Bindings/ManualBindings.cpp
+++ b/src/Bindings/ManualBindings.cpp
@@ -1599,55 +1599,6 @@ static int tolua_cPlayer_GetRestrictions(lua_State * tolua_S)
 
 
 
-static int tolua_cPlayer_OpenWindow(lua_State * tolua_S)
-{
-	// Function signature: cPlayer:OpenWindow(Window)
-
-	// Retrieve the plugin instance from the Lua state
-	cPluginLua * Plugin = cManualBindings::GetLuaPlugin(tolua_S);
-	if (Plugin == nullptr)
-	{
-		return 0;
-	}
-
-	// Get the parameters:
-	cPlayer * self = reinterpret_cast<cPlayer *>(tolua_tousertype(tolua_S, 1, nullptr));
-	cWindow * wnd  = reinterpret_cast<cWindow *>(tolua_tousertype(tolua_S, 2, nullptr));
-	if ((self == nullptr) || (wnd == nullptr))
-	{
-		LOGWARNING("%s: invalid self (%p) or wnd (%p)", __FUNCTION__, static_cast<void *>(self), static_cast<void *>(wnd));
-		return 0;
-	}
-
-	// If cLuaWindow, add a reference, so that Lua won't delete the cLuaWindow object mid-processing
-	tolua_Error err;
-	if (tolua_isusertype(tolua_S, 2, "cLuaWindow", 0, &err))
-	{
-		cLuaWindow * LuaWnd = reinterpret_cast<cLuaWindow *>(wnd);
-		// Only if not already referenced
-		if (!LuaWnd->IsLuaReferenced())
-		{
-			int LuaRef = luaL_ref(tolua_S, LUA_REGISTRYINDEX);
-			if (LuaRef == LUA_REFNIL)
-			{
-				LOGWARNING("%s: Cannot create a window reference. Cannot open window \"%s\".",
-					__FUNCTION__, wnd->GetWindowTitle().c_str()
-				);
-				return 0;
-			}
-			LuaWnd->SetLuaRef(Plugin, LuaRef);
-		}
-	}
-
-	// Open the window
-	self->OpenWindow(wnd);
-	return 0;
-}
-
-
-
-
-
 static int tolua_cPlayer_PermissionMatches(lua_State * tolua_S)
 {
 	// Function signature: cPlayer:PermissionMatches(PermissionStr, TemplateStr) -> bool
@@ -1678,36 +1629,25 @@ static int tolua_cPlayer_PermissionMatches(lua_State * tolua_S)
 
 template <
 	class OBJTYPE,
-	void (OBJTYPE::*SetCallback)(cPluginLua * a_Plugin, int a_FnRef)
+	void (OBJTYPE::*SetCallback)(cLuaState::cCallbackPtr a_CallbackFn)
 >
 static int tolua_SetObjectCallback(lua_State * tolua_S)
 {
 	// Function signature: OBJTYPE:SetWhateverCallback(CallbackFunction)
 
-	// Retrieve the plugin instance from the Lua state
-	cPluginLua * Plugin = cManualBindings::GetLuaPlugin(tolua_S);
-	if (Plugin == nullptr)
-	{
-		// Warning message has already been printed by GetLuaPlugin(), bail out silently
-		return 0;
-	}
-
 	// Get the parameters - self and the function reference:
-	OBJTYPE * self = reinterpret_cast<OBJTYPE *>(tolua_tousertype(tolua_S, 1, nullptr));
-	if (self == nullptr)
-	{
-		LOGWARNING("%s: invalid self (%p)", __FUNCTION__, static_cast<void *>(self));
-		return 0;
-	}
-	int FnRef = luaL_ref(tolua_S, LUA_REGISTRYINDEX);  // Store function reference for later retrieval
-	if (FnRef == LUA_REFNIL)
+	cLuaState L(tolua_S);
+	OBJTYPE * self;
+	cLuaState::cCallbackPtr callback;
+	if (!L.GetStackValues(1, self, callback))
 	{
-		LOGERROR("%s: Cannot create a function reference. Callback not set.", __FUNCTION__);
+		LOGWARNING("%s: Cannot get parameters", __FUNCTION__);
+		L.LogStackTrace();
 		return 0;
 	}
 
 	// Set the callback
-	(self->*SetCallback)(Plugin, FnRef);
+	(self->*SetCallback)(callback);
 	return 0;
 }
 
@@ -2799,6 +2739,79 @@ static int tolua_cLineBlockTracer_Trace(lua_State * tolua_S)
 
 
 
+static int tolua_cLuaWindow_new(lua_State * tolua_S)
+{
+	// Function signature:
+	// cLuaWindow:new(type, slotsX, slotsY, title)
+
+	// Check params:
+	cLuaState L(tolua_S);
+	if (
+		!L.CheckParamUserTable(1, "cLuaWindow") ||
+		!L.CheckParamNumber(2, 4) ||
+		!L.CheckParamString(5) ||
+		!L.CheckParamEnd(6)
+	)
+	{
+		return 0;
+	}
+
+	// Read params:
+	int windowType, slotsX, slotsY;
+	AString title;
+	if (!L.GetStackValues(2, windowType, slotsX, slotsY, title))
+	{
+		LOGWARNING("%s: Cannot read Lua parameters", __FUNCTION__);
+		L.LogStackValues();
+		L.LogStackTrace();
+	}
+
+	// Create the window and return it:
+	L.Push(new cLuaWindow(L, static_cast<cLuaWindow::WindowType>(windowType), slotsX, slotsY, title));
+	return 1;
+}
+
+
+
+
+
+static int tolua_cLuaWindow_new_local(lua_State * tolua_S)
+{
+	// Function signature:
+	// cLuaWindow:new(type, slotsX, slotsY, title)
+
+	// Check params:
+	cLuaState L(tolua_S);
+	if (
+		!L.CheckParamUserTable(1, "cLuaWindow") ||
+		!L.CheckParamNumber(2, 4) ||
+		!L.CheckParamString(5) ||
+		!L.CheckParamEnd(6)
+	)
+	{
+		return 0;
+	}
+
+	// Read params:
+	int windowType, slotsX, slotsY;
+	AString title;
+	if (!L.GetStackValues(2, windowType, slotsX, slotsY, title))
+	{
+		LOGWARNING("%s: Cannot read Lua parameters", __FUNCTION__);
+		L.LogStackValues();
+		L.LogStackTrace();
+	}
+
+	// Create the window, register it for GC and return it:
+	L.Push(new cLuaWindow(L, static_cast<cLuaWindow::WindowType>(windowType), slotsX, slotsY, title));
+	tolua_register_gc(tolua_S, lua_gettop(tolua_S));
+	return 1;
+}
+
+
+
+
+
 static int tolua_cRoot_GetBuildCommitID(lua_State * tolua_S)
 {
 	cLuaState L(tolua_S);
@@ -3642,6 +3655,9 @@ void cManualBindings::Bind(lua_State * tolua_S)
 		tolua_endmodule(tolua_S);
 
 		tolua_beginmodule(tolua_S, "cLuaWindow");
+			tolua_function(tolua_S, "new",              tolua_cLuaWindow_new);
+			tolua_function(tolua_S, "new_local",        tolua_cLuaWindow_new_local);
+			tolua_function(tolua_S, ".call",            tolua_cLuaWindow_new_local);
 			tolua_function(tolua_S, "SetOnClosing",     tolua_SetObjectCallback<cLuaWindow, &cLuaWindow::SetOnClosing>);
 			tolua_function(tolua_S, "SetOnSlotChanged", tolua_SetObjectCallback<cLuaWindow, &cLuaWindow::SetOnSlotChanged>);
 		tolua_endmodule(tolua_S);
@@ -3662,7 +3678,6 @@ void cManualBindings::Bind(lua_State * tolua_S)
 		tolua_beginmodule(tolua_S, "cPlayer");
 			tolua_function(tolua_S, "GetPermissions",    tolua_cPlayer_GetPermissions);
 			tolua_function(tolua_S, "GetRestrictions",   tolua_cPlayer_GetRestrictions);
-			tolua_function(tolua_S, "OpenWindow",        tolua_cPlayer_OpenWindow);
 			tolua_function(tolua_S, "PermissionMatches", tolua_cPlayer_PermissionMatches);
 		tolua_endmodule(tolua_S);
 
diff --git a/src/Entities/Player.h b/src/Entities/Player.h
index 6d092eeb3..bca9c5547 100644
--- a/src/Entities/Player.h
+++ b/src/Entities/Player.h
@@ -225,11 +225,11 @@ public:
 	cWindow * GetWindow(void) { return m_CurrentWindow; }  // tolua_export
 	const cWindow * GetWindow(void) const { return m_CurrentWindow; }
 
-	/** Opens the specified window; closes the current one first using CloseWindow() */
-	void OpenWindow(cWindow * a_Window);  // Exported in ManualBindings.cpp
-
 	// tolua_begin
 
+	/** Opens the specified window; closes the current one first using CloseWindow() */
+	void OpenWindow(cWindow * a_Window);
+
 	/** Closes the current window, resets current window to m_InventoryWindow. A plugin may refuse the closing if a_CanRefuse is true */
 	void CloseWindow(bool a_CanRefuse = true);
 
diff --git a/src/UI/Window.cpp b/src/UI/Window.cpp
index 5a2e55feb..4582d6cf4 100644
--- a/src/UI/Window.cpp
+++ b/src/UI/Window.cpp
@@ -307,7 +307,7 @@ bool cWindow::ClosedByPlayer(cPlayer & a_Player, bool a_CanRefuse)
 	// Checks whether the player is still holding an item
 	if (!a_Player.GetDraggingItem().IsEmpty())
 	{
-		LOGD("Player holds item! Dropping it...");
+		LOGD("Player is holding an item while closing their window, dropping it as a pickup...");
 		a_Player.TossHeldItem(a_Player.GetDraggingItem().m_ItemCount);
 	}