add example of mixed coding of lua and C

Signed-off-by: Neo Xu <neo.xu1990@gmail.com>

examples/examples.lua

@@ -41,6 +41,7 @@ end
 
 createBtn(container, "keyboard")
 createBtn(container, "animation")
+createBtn(container, "luaC")
 createBtn(container, "declarative")
 createBtn(container, "pointer")
 createBtn(container, "analogTime")

examples/luaC.lua

@@ -0,0 +1,4 @@
+-- Everything is already setup in C code, check mixed.c
+-- This file is just to trigger the demo
+
+embed_lua_in_c()

simulator/CMakeLists.txt

@@ -5,7 +5,7 @@ project(simulator)
 add_custom_target(run COMMAND simulator USES_TERMINAL)
 
 file(GLOB_RECURSE WIDGETS ${CMAKE_CURRENT_SOURCE_DIR}/widgets/*.c)
-add_executable(simulator main.c mouse_cursor_icon.c ${WIDGETS})
+add_executable(simulator main.c lua_in_C.c mouse_cursor_icon.c ${WIDGETS})
 target_include_directories(simulator PRIVATE widgets)
 # add_subdirectory(widgets)
 

simulator/lua_in_C.c

@@ -0,0 +1,62 @@
+#include "lua.h"
+#include <luavgl.h>
+#include <lvgl.h>
+#include <src/core/lv_obj.h>
+#include <src/core/lv_obj_event.h>
+#include <src/lv_api_map_v8.h>
+#include <src/misc/lv_event.h>
+
+#define _STRINGIZE(...) #__VA_ARGS__
+#define STRINGIZE(...) _STRINGIZE(__VA_ARGS__)
+
+static const char lua_code_string[] = STRINGIZE(
+    local root = lvgl.get_child_by_id("luaUIroot")
+    root.w = lvgl.VER_RES(),
+    root.h = lvgl.HOR_RES(),
+
+    btn = Button(root, {
+        id = "Button in Lua",
+        Label {
+            text = "Hello, lua, C and lvgl!",
+            align = lvgl.ALIGN_CENTER
+        }
+    }):center()
+);
+
+static void button_clicked(lv_event_t *e)
+{
+  (void)e;
+  lua_State *L = lv_event_get_user_data(e);
+  LV_LOG_USER("Button clicked");
+  luaL_dostring(L, "\
+    local btn = lvgl.get_child_by_id('Button in Lua')\n\
+    local label = btn:get_child(0)\n\
+    label.text = 'Button clicked'\n\
+  ");
+}
+
+static int embed_lua_in_c(lua_State *L)
+{
+  /* We create a root obj in C and create other UIs in lua. */
+  lv_obj_t *root = lv_obj_create(lv_screen_active());
+  luavgl_add_lobj(L, root)->lua_created = false;
+  lv_obj_set_id(root, lv_strdup("luaUIroot"));
+  int ret = luaL_dostring(L, lua_code_string);
+  if (ret != 0) {
+    LV_LOG_USER("luaL_dostring error: %d", ret);
+    return -1;
+  }
+
+  lv_obj_t *btn = lv_obj_get_child_by_id(root, "Button in Lua");
+  if (btn) {
+    lv_obj_add_event_cb(btn, button_clicked, LV_EVENT_CLICKED, L);
+  }
+
+  return 0;
+}
+
+void lua_c_lvgl_mix_example(lua_State *L)
+{
+  lua_pushcfunction(L, embed_lua_in_c);
+  lua_setglobal(L, "embed_lua_in_c");
+}

simulator/main.c

@@ -319,6 +319,10 @@ int main(int argc, char **argv)
   lv_label_set_text(label, "RELOAD");
   lv_obj_center(label);
 
+  void lua_c_lvgl_mix_example(lua_State *L);
+  lua_c_lvgl_mix_example(lua_ctx->L);
+
+
   while (1) {
     /* Periodically call the lv_task handler.
      * It could be done in a timer interrupt or an OS task too.*/