/apps/twnlua: ctx.udata preservation in reload, no export in .so, ignore /data/scripts/twnapi.lua

apps/twnlua/.gitignore

@@ -1 +1,2 @@
 luabind.c
+data/scripts/twnapi.lua

apps/twnlua/bindgen.py

@@ -151,15 +151,12 @@ for typename, typedesc in used_converters.items():
 
 
 print('\n'.join(storages))
-print("extern void bindgen_init(void);\n")
-print("void bindgen_init(void) {\n" + '\n'.join(initializers) + "\n}\n")
 print('\n'.join(converters))
 print('\n'.join(bindings))
 
 
 loader = "extern void bindgen_load_%s(lua_State *L);\n" % api["name"]
 loader += "void bindgen_load_%s(lua_State *L) {\n" % api["name"]
-loader += "    bindgen_init();\n"
 for procedure, procedure_desc in api["procedures"].items():
     loader += "    lua_pushcfunction(L, binding_%s);\n" % procedure
     loader += "    lua_setglobal(L, \"%s\");\n" % procedure

apps/twnlua/data/scripts/game.lua

@@ -4,16 +4,39 @@ offset = { x = 0, y = 0 }
 angle = 0
 
 function game_tick()
+    if ctx.udata == nil then
+        ctx.udata = {
+            frame_count = 0,
+            nest = {
+                frame_count = 0,
+            },
+            arr = { [0] = 0 },
+        }
+    end
+
+    draw_text {
+        string = tostring(ctx.udata.frame_count),
+        position = { x = 0, y = 0 },
+        font = "/fonts/kenney-pixel.ttf",
+    }
+
+    draw_text {
+        string = tostring(ctx.udata.nest.frame_count),
+        position = { x = 0, y = 14 },
+        font = "/fonts/kenney-pixel.ttf",
+    }
+
+    draw_text {
+        string = tostring(ctx.udata.arr[0]),
+        position = { x = 0, y = 28 },
+        font = "/fonts/kenney-pixel.ttf",
+    }
+
     input_action {
         name = "press",
         control = "A"
     }
 
-    draw_rectangle {
-        rect = { x = 0, y = 0, w = 640, h = 360 },
-        color = { r = 127, g = 0, b = 127, a = 255 },
-    }
-
     draw_sprite {
         texture = "/assets/title.png",
         rect = {
@@ -32,6 +55,10 @@ function game_tick()
         }
     end
 
+    ctx.udata.frame_count = ctx.udata.frame_count + 1
+    ctx.udata.nest.frame_count = ctx.udata.nest.frame_count + 1
+    ctx.udata.arr[0] = ctx.udata.arr[0] + 1
+
     offset.x = ORIGIN.x + (math.cos(angle) * RADIUS)
     offset.y = ORIGIN.y + (math.sin(angle) * RADIUS)
     angle = angle + 0.1

apps/twnlua/data/twn.toml

@@ -6,5 +6,6 @@ dev_id = "somebody"
 
 [game]
 resolution = [ 640, 360 ]
+background_color = [ 127, 0, 127, 255 ]
 
 [engine]

apps/twnlua/game.c

@@ -1,5 +1,6 @@
 #include "twn_game_api.h"
 
+/* TODO: actually move it back it its own file, it doesn't give any compilation benefits */
 #define LUA_IMPL
 #include "minilua.h"
 
@@ -8,6 +9,8 @@
 
 #include <SDL2/SDL.h>
 
+#define UDATA_NESTING_LIMIT 128
+
 
 /* generated by bindgen.py */
 void bindgen_load_twn(lua_State *L);
@@ -100,6 +103,47 @@ static void *custom_alloc(void *ud, void *ptr, size_t osize, size_t nsize) {
 }
 
 
+static void exchange_lua_states(lua_State *from, lua_State *to, int level, int index) {
+    if (level >= UDATA_NESTING_LIMIT) {
+        log_critical("ctx.udata nesting limit is reached (%u)", UDATA_NESTING_LIMIT);
+        return;
+    }
+
+    /* TODO: use arrays for optimized paths */
+    /* TODO: preallocate table records */
+    switch (lua_type(from, index)) {
+    case LUA_TTABLE:
+        lua_newtable(to);
+        lua_pushnil(from); /* first key */
+        while (lua_next(from, index - 1) != 0) {
+            /* 'key' at index -2 and 'value' at index -1 */
+            exchange_lua_states(from, to, level + 1, -2);
+            exchange_lua_states(from, to, level + 1, -1);
+            lua_settable(to, index - 2);
+            /* removes 'value'; keeps 'key' for next iteration */
+            lua_pop(from, 1);
+        }
+        break;
+    case LUA_TNUMBER:
+        lua_pushnumber(to, lua_tonumber(from, index));
+        break;
+    case LUA_TBOOLEAN:
+        lua_pushboolean(to, lua_toboolean(from, index));
+        break;
+    case LUA_TSTRING:
+        lua_pushstring(to, lua_tostring(from, index));
+        break;
+    case LUA_TNIL:
+        lua_pushnil(to);
+        break;
+    default:
+        /* TODO: provide a path and type of it for better diagnostic */
+        log_warn("Unserializable udata found and is ignored");
+        break;
+    }
+}
+
+
 void game_tick(void) {
     if (ctx.initialization_needed) {
         if (!ctx.udata)
@@ -108,13 +152,29 @@ void game_tick(void) {
         State *state = ctx.udata;
 
         /* let's init lua */
-        /* state existed already */
+        lua_State *new_state = luaL_newstate();
+        lua_setallocf(new_state, custom_alloc, NULL);
+
+        /* state existed already, copy its udata over */
         if (state->L != NULL) {
+            lua_getglobal(state->L, "ctx");
+            lua_getfield(state->L, -1, "udata");
+            SDL_assert(!lua_isnoneornil(state->L, -1));
+            SDL_assert(!lua_isnoneornil(state->L, -2));
+            // SDL_TriggerBreakpoint();
+            if (!lua_isnoneornil(state->L, -1)) {
+                log_info("Exchanging lua states...");
+                lua_newtable(new_state);
+                exchange_lua_states(state->L, new_state, 0, -1);
+                lua_setfield(new_state, -2, "udata");
+                lua_setglobal(new_state, "ctx");
+            }
+
+            /* bye :) */
             lua_close(state->L);
         }
-        state->L = luaL_newstate();
 
-        lua_setallocf(state->L, custom_alloc, NULL);
+        state->L = new_state;
 
         /* fakey version of luaL_openlibs() that excludes file i/o and os stuff */
         {

apps/twnlua/minilua.h

@@ -383,7 +383,8 @@ extern "C" {
 
 #else				/* }{ */
 
-#define LUA_API		extern
+/* TWN: Don't export anything, there's no need. */
+#define LUA_API		LUAI_FUNC
 
 #endif				/* } */