Add an official core lua context, and allow plugins to send events to it.

- This context requires core suspend lock and asserts it in a few places.
- Special 'event' objects are introduced. They can be invoked as
  functions, in which case they iterate all their fields and call
  them as functions. Errors are printed and consumed.
- When a plugin is opened by the core context, events registered in
  a special array are linked to it. The system is organized so as to
  avoid even trying to pass the event to lua if the module isn't loaded.

LUA_API.rst

@@ -799,3 +799,17 @@ Maps module
 * ``dfhack.maps.setBlockBurrowTile(burrow,block,x,y,enable)``
 
   Adds or removes the tile from the burrow. Returns *false* if invalid coords.
+
+
+Core interpreter context
+========================
+
+While plugins can create any number of interpreter instances,
+there is one special context managed by dfhack core. It is the
+only context that can receive events from DF and plugins.
+
+Core context specific functions:
+
+* ``dfhack.is_core_context``
+
+  Boolean value; *true* in the core context.

Lua API.html

@@ -344,6 +344,7 @@ ul.auto-toc {
 <li><a class="reference internal" href="#maps-module" id="id18">Maps module</a></li>
 </ul>
 </li>
+<li><a class="reference internal" href="#core-interpreter-context" id="id19">Core interpreter context</a></li>
 </ul>
 </li>
 </ul>
@@ -1010,6 +1011,18 @@ Returns <em>false</em> in case of error.</p>
 </ul>
 </div>
 </div>
+<div class="section" id="core-interpreter-context">
+<h2><a class="toc-backref" href="#id19">Core interpreter context</a></h2>
+<p>While plugins can create any number of interpreter instances,
+there is one special context managed by dfhack core. It is the
+only context that can receive events from DF and plugins.</p>
+<p>Core context specific functions:</p>
+<ul>
+<li><p class="first"><tt class="docutils literal">dfhack.is_core_context</tt></p>
+<p>Boolean value; <em>true</em> in the core context.</p>
+</li>
+</ul>
+</div>
 </div>
 </div>
 </body>

library/Core.cpp

@@ -49,6 +49,8 @@ using namespace std;
 #include "modules/Graphic.h"
 #include "modules/Windows.h"
 #include "RemoteServer.h"
+#include "LuaTools.h"
+
 using namespace DFHack;
 
 #include "df/ui.h"
@@ -701,6 +703,9 @@ bool Core::Init()
     virtual_identity::Init(this);
     df::global::InitGlobals();
 
+    // initialize common lua context
+    Lua::Core::Init(con);
+
     // create mutex for syncing with interactive tasks
     misc_data_mutex=new mutex();
     cerr << "Initializing Plugins.\n";
@@ -803,6 +808,13 @@ void *Core::GetData( std::string key )
     }
 }
 
+bool Core::isSuspended(void)
+{
+    lock_guard<mutex> lock(d->AccessMutex);
+
+    return (d->df_suspend_depth > 0 && d->df_suspend_thread == this_thread::get_id());
+}
+
 void Core::Suspend()
 {
     auto tid = this_thread::get_id();
@@ -882,10 +894,13 @@ int Core::Update()
         Init();
         if(errorstate)
             return -1;
+        Lua::Core::Reset(con, "core init");
     }
 
     color_ostream_proxy out(con);
 
+    Lua::Core::Reset(out, "DF code execution");
+
     if (first_update)
         plug_mgr->OnStateChange(out, SC_CORE_INITIALIZED);
 
@@ -976,6 +991,8 @@ int Core::Update()
         assert(d->df_suspend_depth == 0);
         // destroy condition
         delete nc;
+        // check lua stack depth
+        Lua::Core::Reset(con, "suspend");
     }
 
     return 0;

library/LuaApi.cpp

@@ -74,30 +74,7 @@ distribution.
 using namespace DFHack;
 using namespace DFHack::LuaWrapper;
 
-template<class T>
+int Lua::PushPosXYZ(lua_State *state, df::coord pos)
-void push_pointer_vector(lua_State *state, const std::vector<T*> &pvec)
-{
-    lua_createtable(state,pvec.size(),0);
-
-    for (size_t i = 0; i < pvec.size(); i++)
-    {
-        Lua::PushDFObject(state, pvec[i]);
-        lua_rawseti(state, -2, i+1);
-    }
-}
-
-template<class T>
-T *get_checked_arg(lua_State *state, int arg)
-{
-    luaL_checkany(state, arg);
-
-    auto ptr = Lua::GetDFObject<T>(state, arg);
-    if (!ptr)
-        luaL_argerror(state, arg, "invalid type");
-    return ptr;
-}
-
-int push_pos(lua_State *state, df::coord pos)
 {
     if (!pos.isValid())
     {
@@ -570,9 +547,9 @@ static void OpenModule(lua_State *state, const char *mname,
     lua_pop(state, 1);
 }
 
-#define WRAPM(module, function) { #function, df::wrap_function(module::function) }
+#define WRAPM(module, function) { #function, df::wrap_function(module::function,true) }
-#define WRAP(function) { #function, df::wrap_function(function) }
+#define WRAP(function) { #function, df::wrap_function(function,true) }
-#define WRAPN(name, function) { #name, df::wrap_function(function) }
+#define WRAPN(name, function) { #name, df::wrap_function(function,true) }
 
 static const LuaWrapper::FunctionReg dfhack_module[] = {
     WRAPM(Translation, TranslateName),
@@ -613,7 +590,7 @@ static int job_listNewlyCreated(lua_State *state)
     if (Job::listNewlyCreated(&pvec, &nxid))
     {
         lua_pushinteger(state, nxid);
-        push_pointer_vector(state, pvec);
+        Lua::PushVector(state, pvec);
         return 2;
     }
     else
@@ -642,7 +619,7 @@ static const LuaWrapper::FunctionReg dfhack_units_module[] = {
 
 static int units_getPosition(lua_State *state)
 {
-    return push_pos(state, Units::getPosition(get_checked_arg<df::unit>(state,1)));
+    return Lua::PushPosXYZ(state, Units::getPosition(Lua::CheckDFObject<df::unit>(state,1)));
 }
 
 static const luaL_Reg dfhack_units_funcs[] = {
@@ -673,14 +650,14 @@ static const LuaWrapper::FunctionReg dfhack_items_module[] = {
 
 static int items_getPosition(lua_State *state)
 {
-    return push_pos(state, Items::getPosition(get_checked_arg<df::item>(state,1)));
+    return Lua::PushPosXYZ(state, Items::getPosition(Lua::CheckDFObject<df::item>(state,1)));
 }
 
 static int items_getContainedItems(lua_State *state)
 {
     std::vector<df::item*> pvec;
-    Items::getContainedItems(get_checked_arg<df::item>(state,1),&pvec);
+    Items::getContainedItems(Lua::CheckDFObject<df::item>(state,1),&pvec);
-    push_pointer_vector(state, pvec);
+    Lua::PushVector(state, pvec);
     return 1;
 }
 
@@ -719,8 +696,8 @@ static const LuaWrapper::FunctionReg dfhack_maps_module[] = {
 static int maps_listBurrowBlocks(lua_State *state)
 {
     std::vector<df::map_block*> pvec;
-    Maps::listBurrowBlocks(&pvec, get_checked_arg<df::burrow>(state,1));
+    Maps::listBurrowBlocks(&pvec, Lua::CheckDFObject<df::burrow>(state,1));
-    push_pointer_vector(state, pvec);
+    Lua::PushVector(state, pvec);
     return 1;
 }
 

library/LuaTools.cpp

@@ -58,9 +58,18 @@ distribution.
 #include <lauxlib.h>
 #include <lualib.h>
 
+#include <lstate.h>
+
 using namespace DFHack;
 using namespace DFHack::LuaWrapper;
 
+lua_State *DFHack::Lua::Core::State = NULL;
+
+inline void AssertCoreSuspend(lua_State *state)
+{
+    assert(!Lua::IsCoreContext(state) || DFHack::Core::getInstance().isSuspended());
+}
+
 void DFHack::Lua::PushDFObject(lua_State *state, type_identity *type, void *ptr)
 {
     push_object_internal(state, type, ptr, false);
@@ -71,6 +80,36 @@ void *DFHack::Lua::GetDFObject(lua_State *state, type_identity *type, int val_in
     return get_object_internal(state, type, val_index, exact_type, false);
 }
 
+void *DFHack::Lua::CheckDFObject(lua_State *state, type_identity *type, int val_index, bool exact_type)
+{
+    if (lua_type(state, val_index) == LUA_TNONE)
+    {
+        if (val_index > 0)
+            luaL_argerror(state, val_index, "pointer expected");
+        else
+            luaL_error(state, "at index %d: pointer expected", val_index);
+    }
+
+    if (lua_isnil(state, val_index))
+        return NULL;
+
+    void *rv = get_object_internal(state, type, val_index, exact_type, false);
+
+    if (!rv)
+    {
+        std::string error = "invalid pointer type";
+        if (type)
+            error += "; expected: " + type->getFullName();
+
+        if (val_index > 0)
+            luaL_argerror(state, val_index, error.c_str());
+        else
+            luaL_error(state, "at index %d: %s", val_index, error.c_str());
+    }
+
+    return rv;
+}
+
 static int DFHACK_OSTREAM_TOKEN = 0;
 
 color_ostream *DFHack::Lua::GetOutput(lua_State *L)
@@ -418,6 +457,8 @@ static int lua_dfhack_safecall (lua_State *L)
 
 bool DFHack::Lua::SafeCall(color_ostream &out, lua_State *L, int nargs, int nres, bool perr)
 {
+    AssertCoreSuspend(L);
+
     int base = lua_gettop(L) - nargs;
 
     color_ostream *cur_out = Lua::GetOutput(L);
@@ -440,13 +481,52 @@ bool DFHack::Lua::SafeCall(color_ostream &out, lua_State *L, int nargs, int nres
     return ok;
 }
 
-bool DFHack::Lua::Require(color_ostream &out, lua_State *state,
+static int DFHACK_LOADED_TOKEN = 0;
-                          const std::string &module, bool setglobal)
+
+bool DFHack::Lua::PushModule(color_ostream &out, lua_State *state, const char *module)
 {
+    AssertCoreSuspend(state);
+
+    // Check if it is already loaded
+    lua_rawgetp(state, LUA_REGISTRYINDEX, &DFHACK_LOADED_TOKEN);
+    lua_pushstring(state, module);
+    lua_rawget(state, -2);
+
+    if (lua_toboolean(state, -1))
+    {
+        lua_remove(state, -2);
+        return true;
+    }
+
+    lua_pop(state, 2);
     lua_getglobal(state, "require");
-    lua_pushstring(state, module.c_str());
+    lua_pushstring(state, module);
 
-    if (!Lua::SafeCall(out, state, 1, 1))
+    return Lua::SafeCall(out, state, 1, 1);
+}
+
+bool DFHack::Lua::PushModulePublic(color_ostream &out, lua_State *state,
+                                   const char *module, const char *name)
+{
+    if (!PushModule(out, state, module))
+        return false;
+
+    if (!lua_istable(state, -1))
+    {
+        lua_pop(state, 1);
+        return false;
+    }
+
+    lua_pushstring(state, name);
+    lua_rawget(state, -2);
+    lua_remove(state, -2);
+    return true;
+}
+
+bool DFHack::Lua::Require(color_ostream &out, lua_State *state,
+                          const std::string &module, bool setglobal)
+{
+    if (!PushModule(out, state, module.c_str()))
         return false;
 
     if (setglobal)
@@ -471,6 +551,8 @@ bool DFHack::Lua::SafeCallString(color_ostream &out, lua_State *state, const std
                                  int nargs, int nres, bool perr,
                                  const char *debug_tag, int env_idx)
 {
+    AssertCoreSuspend(state);
+
     if (!debug_tag)
         debug_tag = code.c_str();
     if (env_idx)
@@ -507,6 +589,8 @@ bool DFHack::Lua::SafeCallString(color_ostream &out, lua_State *state, const std
 bool DFHack::Lua::InterpreterLoop(color_ostream &out, lua_State *state,
                                   const char *prompt, int env, const char *hfile)
 {
+    AssertCoreSuspend(state);
+
     if (!out.is_console())
         return false;
     if (!lua_checkstack(state, 20))
@@ -761,6 +845,15 @@ static int dfhack_open_plugin(lua_State *L)
     return 0;
 }
 
+bool Lua::IsCoreContext(lua_State *state)
+{
+    // This uses a private field of the lua state to
+    // evaluate the condition without accessing the lua
+    // stack, and thus requiring a lock on the core state.
+    return state && Lua::Core::State &&
+           state->l_G == Lua::Core::State->l_G;
+}
+
 static const luaL_Reg dfhack_funcs[] = {
     { "print", lua_dfhack_print },
     { "println", lua_dfhack_println },
@@ -777,6 +870,132 @@ static const luaL_Reg dfhack_funcs[] = {
     { NULL, NULL }
 };
 
+/************
+ *  Events  *
+ ************/
+
+static int DFHACK_EVENT_META_TOKEN = 0;
+
+int DFHack::Lua::NewEvent(lua_State *state)
+{
+    lua_newtable(state);
+    lua_rawgetp(state, LUA_REGISTRYINDEX, &DFHACK_EVENT_META_TOKEN);
+    lua_setmetatable(state, -2);
+    return 1;
+}
+
+static void dfhack_event_invoke(lua_State *L, int base, bool from_c)
+{
+    int event = base+1;
+    int num_args = lua_gettop(L)-event;
+
+    int errorfun = base+2;
+    lua_pushcfunction(L, dfhack_onerror);
+    lua_insert(L, errorfun);
+
+    int argbase = base+3;
+    lua_pushnil(L);
+
+    // stack: |base| event errorfun (args) key cb (args)
+
+    while (lua_next(L, event))
+    {
+        if (from_c && lua_islightuserdata(L, -1) && !lua_touserdata(L, -1))
+            continue;
+
+        for (int i = 0; i < num_args; i++)
+            lua_pushvalue(L, argbase+i);
+
+        if (lua_pcall(L, num_args, 0, errorfun) != LUA_OK)
+        {
+            report_error(L);
+            lua_pop(L, 1);
+        }
+    }
+
+    lua_settop(L, base);
+}
+
+static int dfhack_event_call(lua_State *state)
+{
+    luaL_checktype(state, 1, LUA_TTABLE);
+    luaL_checkstack(state, lua_gettop(state)+2, "stack overflow in event dispatch");
+
+    dfhack_event_invoke(state, 0, false);
+    return 0;
+}
+
+void DFHack::Lua::InvokeEvent(color_ostream &out, lua_State *state, void *key, int num_args)
+{
+    AssertCoreSuspend(state);
+
+    int base = lua_gettop(state) - num_args;
+
+    if (!lua_checkstack(state, num_args+4))
+    {
+        out.printerr("Stack overflow in Lua::InvokeEvent");
+        lua_settop(state, base);
+        return;
+    }
+
+    lua_rawgetp(state, LUA_REGISTRYINDEX, key);
+
+    if (!lua_istable(state, -1))
+    {
+        if (!lua_isnil(state, -1))
+            out.printerr("Invalid event object in Lua::InvokeEvent");
+        lua_settop(state, base);
+        return;
+    }
+
+    lua_insert(state, base+1);
+
+    color_ostream *cur_out = Lua::GetOutput(state);
+    set_dfhack_output(state, &out);
+    dfhack_event_invoke(state, base, true);
+    set_dfhack_output(state, cur_out);
+}
+
+void DFHack::Lua::CreateEvent(lua_State *state, void *key)
+{
+    lua_rawgetp(state, LUA_REGISTRYINDEX, key);
+
+    if (lua_isnil(state, -1))
+    {
+        lua_pop(state, 1);
+        NewEvent(state);
+    }
+
+    lua_dup(state);
+    lua_rawsetp(state, LUA_REGISTRYINDEX, key);
+}
+
+void DFHack::Lua::Notification::invoke(color_ostream &out, int nargs)
+{
+    assert(state);
+    InvokeEvent(out, state, key, nargs);
+}
+
+void DFHack::Lua::Notification::bind(lua_State *state, void *key)
+{
+    this->state = state;
+    this->key = key;
+}
+
+void DFHack::Lua::Notification::bind(lua_State *state, const char *name)
+{
+    CreateEvent(state, this);
+
+    if (handler)
+    {
+        PushFunctionWrapper(state, 0, name, handler);
+        lua_rawsetp(state, -2, NULL);
+    }
+
+    this->state = state;
+    this->key = this;
+}
+
 /************************
  *  Main Open function  *
  ************************/
@@ -798,6 +1017,9 @@ lua_State *DFHack::Lua::Open(color_ostream &out, lua_State *state)
     // Create the dfhack global
     lua_newtable(state);
 
+    lua_pushboolean(state, IsCoreContext(state));
+    lua_setfield(state, -2, "is_core_context");
+
     // Create the metatable for exceptions
     lua_newtable(state);
     lua_pushcfunction(state, dfhack_exception_tostring);
@@ -806,6 +1028,15 @@ lua_State *DFHack::Lua::Open(color_ostream &out, lua_State *state)
     lua_rawsetp(state, LUA_REGISTRYINDEX, &DFHACK_EXCEPTION_META_TOKEN);
     lua_setfield(state, -2, "exception");
 
+    lua_newtable(state);
+    lua_pushcfunction(state, dfhack_event_call);
+    lua_setfield(state, -2, "__call");
+    lua_pushcfunction(state, Lua::NewEvent);
+    lua_setfield(state, -2, "new");
+    lua_dup(state);
+    lua_rawsetp(state, LUA_REGISTRYINDEX, &DFHACK_EVENT_META_TOKEN);
+    lua_setfield(state, -2, "event");
+
     // Initialize the dfhack global
     luaL_setfuncs(state, dfhack_funcs, 0);
 
@@ -813,9 +1044,40 @@ lua_State *DFHack::Lua::Open(color_ostream &out, lua_State *state)
 
     lua_setglobal(state, "dfhack");
 
+    // stash the loaded module table into our own registry key
+    lua_getglobal(state, "package");
+    assert(lua_istable(state, -1));
+    lua_getfield(state, -1, "loaded");
+    assert(lua_istable(state, -1));
+    lua_rawsetp(state, LUA_REGISTRYINDEX, &DFHACK_LOADED_TOKEN);
+    lua_pop(state, 1);
+
     // load dfhack.lua
     Require(out, state, "dfhack");
 
+    lua_settop(state, 0);
+    if (!lua_checkstack(state, 64))
+        out.printerr("Could not extend initial lua stack size to 64 items.\n");
+
     return state;
 }
 
+void DFHack::Lua::Core::Init(color_ostream &out)
+{
+    if (State)
+        return;
+
+    State = luaL_newstate();
+    Lua::Open(out, State);
+}
+
+void DFHack::Lua::Core::Reset(color_ostream &out, const char *where)
+{
+    int top = lua_gettop(State);
+
+    if (top != 0)
+    {
+        out.printerr("Common lua context stack top left at %d after %s.\n", top, where);
+        lua_settop(State, 0);
+    }
+}

library/LuaTypes.cpp

@@ -1036,7 +1036,9 @@ static int meta_call_function(lua_State *state)
 
 int LuaWrapper::method_wrapper_core(lua_State *state, function_identity_base *id)
 {
-    if (lua_gettop(state) != id->getNumArgs())
+    if (id->adjustArgs())
+        lua_settop(state, id->getNumArgs());
+    else if (lua_gettop(state) != id->getNumArgs())
         field_error(state, UPVAL_METHOD_NAME, "invalid argument count", "invoke");
 
     try {
@@ -1056,9 +1058,9 @@ int LuaWrapper::method_wrapper_core(lua_State *state, function_identity_base *id
 }
 
 /**
- * Create a closure invoking the given function, and add it to the field table.
+ * Push a closure invoking the given function.
  */
-static void AddMethodWrapper(lua_State *state, int meta_idx, int field_idx,
+void LuaWrapper::PushFunctionWrapper(lua_State *state, int meta_idx,
                                      const char *name, function_identity_base *fun)
 {
     lua_rawgetp(state, LUA_REGISTRYINDEX, &DFHACK_TYPETABLE_TOKEN);
@@ -1069,7 +1071,15 @@ static void AddMethodWrapper(lua_State *state, int meta_idx, int field_idx,
     lua_pushfstring(state, "%s()", name);
     lua_pushlightuserdata(state, fun);
     lua_pushcclosure(state, meta_call_function, 4);
+}
 
+/**
+ * Create a closure invoking the given function, and add it to the field table.
+ */
+static void AddMethodWrapper(lua_State *state, int meta_idx, int field_idx,
+                             const char *name, function_identity_base *fun)
+{
+    PushFunctionWrapper(state, meta_idx, name, fun);
     lua_setfield(state, field_idx, name);
 }
 

library/PluginManager.cpp

@@ -33,6 +33,7 @@ distribution.
 #include "MiscUtils.h"
 
 #include "LuaWrapper.h"
+#include "LuaTools.h"
 
 using namespace DFHack;
 
@@ -380,6 +381,7 @@ command_result Plugin::on_update(color_ostream &out)
     if(state == PS_LOADED && plugin_onupdate)
     {
         cr = plugin_onupdate(out);
+        Lua::Core::Reset(out, "plugin_onupdate");
     }
     access->lock_sub();
     return cr;
@@ -392,6 +394,7 @@ command_result Plugin::on_state_change(color_ostream &out, state_change_event ev
     if(state == PS_LOADED && plugin_onstatechange)
     {
         cr = plugin_onstatechange(out, event);
+        Lua::Core::Reset(out, "plugin_onstatechange");
     }
     access->lock_sub();
     return cr;
@@ -445,9 +448,7 @@ void Plugin::index_lua(DFLibrary *lib)
         for (; cmdlist->name; ++cmdlist)
         {
             auto &cmd = lua_commands[cmdlist->name];
-            if (!cmd) cmd = new LuaCommand;
+            if (!cmd) cmd = new LuaCommand(this,cmdlist->name);
-            cmd->owner = this;
-            cmd->name = cmdlist->name;
             cmd->command = cmdlist->command;
         }
     }
@@ -456,12 +457,22 @@ void Plugin::index_lua(DFLibrary *lib)
         for (; funlist->name; ++funlist)
         {
             auto &cmd = lua_functions[funlist->name];
-            if (!cmd) cmd = new LuaFunction;
+            if (!cmd) cmd = new LuaFunction(this,funlist->name);
-            cmd->owner = this;
-            cmd->name = funlist->name;
             cmd->identity = funlist->identity;
         }
     }
+    if (auto evlist = (EventReg*)LookupPlugin(lib, "plugin_lua_events"))
+    {
+        for (; evlist->name; ++evlist)
+        {
+            auto &cmd = lua_events[evlist->name];
+            if (!cmd) cmd = new LuaEvent(this,evlist->name);
+            cmd->handler.identity = evlist->event->get_handler();
+            cmd->event = evlist->event;
+            if (cmd->active)
+                cmd->event->bind(Lua::Core::State, cmd);
+        }
+    }
 }
 
 void Plugin::reset_lua()
@@ -470,6 +481,11 @@ void Plugin::reset_lua()
         it->second->command = NULL;
     for (auto it = lua_functions.begin(); it != lua_functions.end(); ++it)
         it->second->identity = NULL;
+    for (auto it = lua_events.begin(); it != lua_events.end(); ++it)
+    {
+        it->second->handler.identity = NULL;
+        it->second->event = NULL;
+    }
 }
 
 int Plugin::lua_cmd_wrapper(lua_State *state)
@@ -512,14 +528,36 @@ void Plugin::open_lua(lua_State *state, int table)
     }
 
     for (auto it = lua_functions.begin(); it != lua_functions.end(); ++it)
+    {
+        push_function(state, it->second);
+        lua_setfield(state, table, it->first.c_str());
+    }
+
+    if (Lua::IsCoreContext(state))
+    {
+        for (auto it = lua_events.begin(); it != lua_events.end(); ++it)
+        {
+            Lua::CreateEvent(state, it->second);
+
+            push_function(state, &it->second->handler);
+            lua_rawsetp(state, -2, NULL);
+
+            it->second->active = true;
+            if (it->second->event)
+                it->second->event->bind(state, it->second);
+
+            lua_setfield(state, table, it->first.c_str());
+        }
+    }
+}
+
+void Plugin::push_function(lua_State *state, LuaFunction *fn)
 {
     lua_rawgetp(state, LUA_REGISTRYINDEX, &LuaWrapper::DFHACK_TYPETABLE_TOKEN);
     lua_pushlightuserdata(state, NULL);
-        lua_pushfstring(state, "%s.%s()", name.c_str(), it->second->name.c_str());
+    lua_pushfstring(state, "%s.%s()", name.c_str(), fn->name.c_str());
-        lua_pushlightuserdata(state, it->second);
+    lua_pushlightuserdata(state, fn);
     lua_pushcclosure(state, lua_fun_wrapper, 4);
-        lua_setfield(state, table, it->first.c_str());
-    }
 }
 
 PluginManager::PluginManager(Core * core)

library/include/Core.h

@@ -90,6 +90,8 @@ namespace DFHack
             static Core instance;
             return instance;
         }
+        /// check if the activity lock is owned by this thread
+        bool isSuspended(void);
         /// try to acquire the activity lock
         void Suspend(void);
         /// return activity lock

library/include/DataFuncs.h

@@ -161,15 +161,15 @@ INSTANTIATE_WRAPPERS(5, (A1,A2,A3,A4,A5), (vA1,vA2,vA3,vA4,vA5),
     public:
         typedef function_wrapper<T> wrapper;
 
-        function_identity(T ptr)
+        function_identity(T ptr, bool vararg)
-            : function_identity_base(wrapper::num_args), ptr(ptr) {};
+            : function_identity_base(wrapper::num_args, vararg), ptr(ptr) {};
 
         virtual void invoke(lua_State *state, int base) { wrapper::execute(state, base, ptr); }
     };
 
     template<class T>
-    inline function_identity_base *wrap_function(T ptr) {
+    inline function_identity_base *wrap_function(T ptr, bool vararg = false) {
         // bah, but didn't have any idea how to allocate statically
-        return new function_identity<T>(ptr);
+        return new function_identity<T>(ptr, vararg);
     }
 }

library/include/DataIdentity.h

@@ -39,13 +39,17 @@ namespace DFHack
 {
     class DFHACK_EXPORT function_identity_base : public type_identity {
         int num_args;
+        bool vararg;
 
     public:
-        function_identity_base(int num_args) : type_identity(0), num_args(num_args) {};
+        function_identity_base(int num_args, bool vararg = false)
+            : type_identity(0), num_args(num_args), vararg(vararg) {};
 
         virtual identity_type type() { return IDTYPE_FUNCTION; }
 
         int getNumArgs() { return num_args; }
+        bool adjustArgs() { return vararg; }
+
         std::string getFullName() { return "function"; }
 
         virtual void invoke(lua_State *state, int base) = 0;

library/include/LuaTools.h

@@ -34,6 +34,10 @@ distribution.
 #include <lua.h>
 #include <lauxlib.h>
 
+namespace DFHack {
+    class function_identity_base;
+}
+
 namespace DFHack {namespace Lua {
     /**
      * Create or initialize a lua interpreter with access to DFHack tools.
@@ -41,11 +45,22 @@ namespace DFHack { namespace Lua {
     DFHACK_EXPORT lua_State *Open(color_ostream &out, lua_State *state = NULL);
 
     /**
-     * Load a module using require().
+     * Load a module using require(). Leaves the stack as is.
      */
     DFHACK_EXPORT bool Require(color_ostream &out, lua_State *state,
                                const std::string &module, bool setglobal = false);
 
+    /**
+     * Push the module table, loading it using require() if necessary.
+     */
+    DFHACK_EXPORT bool PushModule(color_ostream &out, lua_State *state, const char *module);
+
+    /**
+     * Push the public object name exported by the module. Uses PushModule.
+     */
+    DFHACK_EXPORT bool PushModulePublic(color_ostream &out, lua_State *state,
+                                        const char *module, const char *name);
+
     /**
      * Check if the object at the given index is NIL or NULL.
      */
@@ -79,6 +94,12 @@ namespace DFHack { namespace Lua {
      */
     DFHACK_EXPORT void *GetDFObject(lua_State *state, type_identity *type, int val_index, bool exact_type = false);
 
+    /**
+     * Check that the value is a wrapped DF object of the given type, and if so return the pointer.
+     * Otherwise throw an argument type error.
+     */
+    DFHACK_EXPORT void *CheckDFObject(lua_State *state, type_identity *type, int val_index, bool exact_type = false);
+
     /**
      * Assign the value at val_index to the target of given identity using df.assign().
      * Return behavior is of SafeCall below.
@@ -102,6 +123,14 @@ namespace DFHack { namespace Lua {
         return (T*)GetDFObject(state, df::identity_traits<T>::get(), val_index, exact_type);
     }
 
+    /**
+     * Check that the value is a wrapped DF object of the correct type, and if so return the pointer. Otherwise throw an argument type error.
+     */
+    template<class T>
+    T *CheckDFObject(lua_State *state, int val_index, bool exact_type = false) {
+        return (T*)CheckDFObject(state, df::identity_traits<T>::get(), val_index, exact_type);
+    }
+
     /**
      * Assign the value at val_index to the target using df.assign().
      */
@@ -134,5 +163,146 @@ namespace DFHack { namespace Lua {
      */
     DFHACK_EXPORT bool InterpreterLoop(color_ostream &out, lua_State *state,
                                        const char *prompt = NULL, int env = 0, const char *hfile = NULL);
+
+    /**
+     * Push utility functions
+     */
+#define NUMBER_PUSH(type) inline void Push(lua_State *state, type value) { lua_pushnumber(state, value); }
+    NUMBER_PUSH(char)
+    NUMBER_PUSH(int8_t) NUMBER_PUSH(uint8_t)
+    NUMBER_PUSH(int16_t) NUMBER_PUSH(uint16_t)
+    NUMBER_PUSH(int32_t) NUMBER_PUSH(uint32_t)
+    NUMBER_PUSH(int64_t) NUMBER_PUSH(uint64_t)
+    NUMBER_PUSH(float) NUMBER_PUSH(double)
+#undef NUMBER_PUSH
+    inline void Push(lua_State *state, bool value) {
+        lua_pushboolean(state, value);
+    }
+    inline void Push(lua_State *state, const std::string &str) {
+        lua_pushlstring(state, str.data(), str.size());
+    }
+    inline void Push(lua_State *state, df::coord &obj) { PushDFObject(state, &obj); }
+    inline void Push(lua_State *state, df::coord2d &obj) { PushDFObject(state, &obj); }
+    template<class T> inline void Push(lua_State *state, T *ptr) {
+        PushDFObject(state, ptr);
+    }
+
+    template<class T>
+    void PushVector(lua_State *state, const T &pvec)
+    {
+        lua_createtable(state,pvec.size(),0);
+
+        for (size_t i = 0; i < pvec.size(); i++)
+        {
+            Push(state, pvec[i]);
+            lua_rawseti(state, -2, i+1);
+        }
+    }
+
+    DFHACK_EXPORT int PushPosXYZ(lua_State *state, df::coord pos);
+
+    DFHACK_EXPORT bool IsCoreContext(lua_State *state);
+
+    DFHACK_EXPORT int NewEvent(lua_State *state);
+    DFHACK_EXPORT void CreateEvent(lua_State *state, void *key);
+    DFHACK_EXPORT void InvokeEvent(color_ostream &out, lua_State *state, void *key, int num_args);
+
+    /**
+     * Namespace for the common lua interpreter state.
+     * All accesses must be done under CoreSuspender.
+     */
+    namespace Core {
+        DFHACK_EXPORT extern lua_State *State;
+
+        // Not exported; for use by the Core class
+        void Init(color_ostream &out);
+        void Reset(color_ostream &out, const char *where);
+
+        template<class T> inline void Push(T &arg) { Lua::Push(State, arg); }
+        template<class T> inline void Push(const T &arg) { Lua::Push(State, arg); }
+        template<class T> inline void PushVector(const T &arg) { Lua::PushVector(State, arg); }
+
+        inline bool SafeCall(color_ostream &out, int nargs, int nres, bool perr = true) {
+            return Lua::SafeCall(out, State, nargs, nres, perr);
+        }
+        inline bool PushModule(color_ostream &out, const char *module) {
+            return Lua::PushModule(out, State, module);
+        }
+        inline bool PushModulePublic(color_ostream &out, const char *module, const char *name) {
+            return Lua::PushModulePublic(out, State, module, name);
+        }
+    }
+
+    class DFHACK_EXPORT Notification {
+        lua_State *state;
+        void *key;
+        function_identity_base *handler;
+
+    public:
+        Notification(function_identity_base *handler = NULL)
+            : state(NULL), key(NULL), handler(handler) {}
+
+        lua_State *get_state() { return state; }
+        function_identity_base *get_handler() { return handler; }
+
+        void invoke(color_ostream &out, int nargs);
+
+        void bind(lua_State *state, const char *name);
+        void bind(lua_State *state, void *key);
+    };
 }}
 
+#define DEFINE_LUA_EVENT_0(name, handler) \
+    static DFHack::Lua::Notification name##_event(df::wrap_function(handler, true)); \
+    void name(color_ostream &out) { \
+        handler(out); \
+        if (name##_event.get_state()) { \
+            name##_event.invoke(out, 0); \
+        } \
+    }
+
+#define DEFINE_LUA_EVENT_1(name, handler, arg_type1) \
+    static DFHack::Lua::Notification name##_event(df::wrap_function(handler, true)); \
+    void name(color_ostream &out, arg_type1 arg1) { \
+        handler(out, arg1); \
+        if (auto state = name##_event.get_state()) { \
+            DFHack::Lua::Push(state, arg1); \
+            name##_event.invoke(out, 1); \
+        } \
+    }
+
+#define DEFINE_LUA_EVENT_2(name, handler, arg_type1, arg_type2) \
+    static DFHack::Lua::Notification name##_event(df::wrap_function(handler, true)); \
+    void name(color_ostream &out, arg_type1 arg1, arg_type2 arg2) { \
+        handler(out, arg1, arg2); \
+        if (auto state = name##_event.get_state()) { \
+            DFHack::Lua::Push(state, arg1); \
+            DFHack::Lua::Push(state, arg2); \
+            name##_event.invoke(out, 2); \
+        } \
+    }
+
+#define DEFINE_LUA_EVENT_3(name, handler, arg_type1, arg_type2, arg_type3) \
+    static DFHack::Lua::Notification name##_event(df::wrap_function(handler, true)); \
+    void name(color_ostream &out, arg_type1 arg1, arg_type2 arg2, arg_type3 arg3) { \
+        handler(out, arg1, arg2, arg3); \
+        if (auto state = name##_event.get_state()) { \
+            DFHack::Lua::Push(state, arg1); \
+            DFHack::Lua::Push(state, arg2); \
+            DFHack::Lua::Push(state, arg3); \
+            name##_event.invoke(out, 3); \
+        } \
+    }
+
+#define DEFINE_LUA_EVENT_4(name, handler, arg_type1, arg_type2, arg_type3, arg_type4) \
+    static DFHack::Lua::Notification name##_event(df::wrap_function(handler, true)); \
+    void name(color_ostream &out, arg_type1 arg1, arg_type2 arg2, arg_type3 arg3, arg_type4 arg4) { \
+        handler(out, arg1, arg2, arg3, arg4); \
+        if (auto state = name##_event.get_state()) { \
+            DFHack::Lua::Push(state, arg1); \
+            DFHack::Lua::Push(state, arg2); \
+            DFHack::Lua::Push(state, arg3); \
+            DFHack::Lua::Push(state, arg4); \
+            name##_event.invoke(out, 4); \
+        } \
+    }

library/include/LuaWrapper.h

@@ -222,6 +222,12 @@ namespace DFHack { namespace LuaWrapper {
      */
     void AttachEnumKeys(lua_State *state, int meta_idx, int ftable_idx, type_identity *ienum);
 
+    /**
+     * Push a closure invoking the given function.
+     */
+    void PushFunctionWrapper(lua_State *state, int meta_idx,
+                             const char *name, function_identity_base *fun);
+
     /**
      * Wrap functions and add them to the table on the top of the stack.
      */

library/include/PluginManager.h

@@ -51,6 +51,9 @@ namespace DFHack
     class virtual_identity;
     class RPCService;
     class function_identity_base;
+    namespace Lua {
+        class Notification;
+    }
 
     // anon type, pretty much
     struct DFLibrary;
@@ -80,6 +83,10 @@ namespace DFHack
         const char *name;
         function_identity_base *identity;
     };
+    struct DFHACK_EXPORT EventReg {
+        const char *name;
+        Lua::Notification *event;
+    };
     struct DFHACK_EXPORT PluginCommand
     {
         typedef command_result (*command_function)(color_ostream &out, std::vector <std::string> &);
@@ -178,6 +185,7 @@ namespace DFHack
             Plugin *owner;
             std::string name;
             int (*command)(lua_State *state);
+            LuaCommand(Plugin *owner, std::string name) : owner(owner), name(name) {}
         };
         std::map<std::string, LuaCommand*> lua_commands;
         static int lua_cmd_wrapper(lua_State *state);
@@ -186,9 +194,19 @@ namespace DFHack
             Plugin *owner;
             std::string name;
             function_identity_base *identity;
+            LuaFunction(Plugin *owner, std::string name) : owner(owner), name(name) {}
         };
         std::map<std::string, LuaFunction*> lua_functions;
         static int lua_fun_wrapper(lua_State *state);
+        void push_function(lua_State *state, LuaFunction *fn);
+
+        struct LuaEvent {
+            LuaFunction handler;
+            Lua::Notification *event;
+            bool active;
+            LuaEvent(Plugin *owner, std::string name) : handler(owner,name), active(false) {}
+        };
+        std::map<std::string, LuaEvent*> lua_events;
 
         void index_lua(DFLibrary *lib);
         void reset_lua();
@@ -253,7 +271,10 @@ namespace DFHack
     DFhackCExport const DFHack::CommandReg plugin_lua_commands[] =
 #define DFHACK_PLUGIN_LUA_FUNCTIONS \
     DFhackCExport const DFHack::FunctionReg plugin_lua_functions[] =
+#define DFHACK_PLUGIN_LUA_EVENTS \
+    DFhackCExport const DFHack::EventReg plugin_lua_events[] =
 
 #define DFHACK_LUA_COMMAND(name) { #name, name }
-#define DFHACK_LUA_FUNCTION(name) { #name, df::wrap_function(name) }
+#define DFHACK_LUA_FUNCTION(name) { #name, df::wrap_function(name,true) }
+#define DFHACK_LUA_EVENT(name) { #name, &name##_event }
 #define DFHACK_LUA_END { NULL, NULL }

library/lua/dfhack.lua

@@ -105,6 +105,10 @@ function xyz2pos(x,y,z)
     end
 end
 
+function dfhack.event:__tostring()
+    return "<event>"
+end
+
 function dfhack.persistent:__tostring()
     return "<persistent "..self.entry_id..":"..self.key.."=\""
            ..self.value.."\":"..table.concat(self.ints,",")..">"

plugins/Dfusion/dfusion.cpp

@@ -121,6 +121,13 @@ command_result lua_run_file (color_ostream &out, std::vector <std::string> &para
 }
 command_result lua_run (color_ostream &out, std::vector <std::string> &parameters)
 {
+    if (!parameters.empty() && parameters[0] == "--core-context")
+    {
+        CoreSuspender suspend;
+        Lua::InterpreterLoop(out, Lua::Core::State);
+        return CR_OK;
+    }
+
 	mymutex->lock();
 	lua::state s=lua::glua::Get();
 

plugins/burrows.cpp

@@ -5,6 +5,7 @@
 #include "Error.h"
 
 #include "DataFuncs.h"
+#include "LuaTools.h"
 
 #include "modules/Gui.h"
 #include "modules/Job.h"
@@ -121,6 +122,8 @@ static int name_burrow_id = -1;
 
 static void handle_burrow_rename(color_ostream &out, df::burrow *burrow);
 
+DEFINE_LUA_EVENT_1(onBurrowRename, handle_burrow_rename, df::burrow*);
+
 static void detect_burrow_renames(color_ostream &out)
 {
     if (ui->main.mode == ui_sidebar_mode::Burrows &&
@@ -134,7 +137,7 @@ static void detect_burrow_renames(color_ostream &out)
         auto burrow = df::burrow::find(name_burrow_id);
         name_burrow_id = -1;
         if (burrow)
-            handle_burrow_rename(out, burrow);
+            onBurrowRename(out, burrow);
     }
 }
 
@@ -151,6 +154,9 @@ static std::map<int,DigJob> diggers;
 static void handle_dig_complete(color_ostream &out, df::job_type job, df::coord pos,
                                 df::tiletype old_tile, df::tiletype new_tile);
 
+DEFINE_LUA_EVENT_4(onDigComplete, handle_dig_complete,
+                   df::job_type, df::coord, df::tiletype, df::tiletype);
+
 static void detect_digging(color_ostream &out)
 {
     for (auto it = diggers.begin(); it != diggers.end();)
@@ -172,7 +178,7 @@ static void detect_digging(color_ostream &out)
 
                 if (new_tile != it->second.old_tile)
                 {
-                    handle_dig_complete(out, it->second.job, pos, it->second.old_tile, new_tile);
+                    onDigComplete(out, it->second.job, pos, it->second.old_tile, new_tile);
 
                     //if (worker && !worker->job.current_job)
                     //    worker->counters.think_counter = worker->counters.job_counter = 0;
@@ -410,6 +416,17 @@ static void handle_dig_complete(color_ostream &out, df::job_type job, df::coord
     }
 }
 
+static void renameBurrow(color_ostream &out, df::burrow *burrow, std::string name)
+{
+    CHECK_NULL_POINTER(burrow);
+
+    // The event makes this absolutely necessary
+    CoreSuspender suspend;
+
+    burrow->name = name;
+    onBurrowRename(out, burrow);
+}
+
 static df::burrow *findByName(color_ostream &out, std::string name, bool silent = false)
 {
     int id = -1;
@@ -552,6 +569,7 @@ static bool setTilesByKeyword(df::burrow *target, std::string name, bool enable)
 }
 
 DFHACK_PLUGIN_LUA_FUNCTIONS {
+    DFHACK_LUA_FUNCTION(renameBurrow),
     DFHACK_LUA_FUNCTION(findByName),
     DFHACK_LUA_FUNCTION(copyUnits),
     DFHACK_LUA_FUNCTION(copyTiles),
@@ -559,6 +577,12 @@ DFHACK_PLUGIN_LUA_FUNCTIONS {
     DFHACK_LUA_END
 };
 
+DFHACK_PLUGIN_LUA_EVENTS {
+    DFHACK_LUA_EVENT(onBurrowRename),
+    DFHACK_LUA_EVENT(onDigComplete),
+    DFHACK_LUA_END
+};
+
 static command_result burrow(color_ostream &out, vector <string> &parameters)
 {
     CoreSuspender suspend;