Add example of mixed UI programming with Lua and C

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()

examples/objid.lua

@@ -0,0 +1,46 @@
+local lvgl = require("lvgl")
+
+local container = lvgl.Label {
+    w = lvgl.HOR_RES(),
+    h = lvgl.VER_RES(),
+    bg_color = "#888",
+    bg_opa = lvgl.OPA(100),
+    border_width = 0,
+    radius = 0,
+    flex = {
+        flex_direction = "row",
+        flex_wrap = "wrap"
+    }
+}
+
+local obj1 = container:Object()
+obj1.id = "Obj1"
+
+local obj2 = obj1:Object()
+obj2.id = "child"
+
+local obj3 = container:Object()
+obj3.id = "Obj3"
+
+local obj4 = obj3:Object()
+obj4.id = "child"
+
+local failed = false
+local obj = lvgl.get_child_by_id("Obj1") -- obj1
+failed = failed or obj ~= obj1
+print("obj id", obj.id)
+
+local obj = obj1:get_child_by_id("child") -- obj1
+print("obj id", obj.id, obj == obj2)
+failed = failed or obj ~= obj2
+
+
+local obj = obj3:get_child_by_id("child") -- obj1
+print("obj id", obj.id, obj == obj4)
+failed = failed or obj ~= obj4
+
+lvgl.Label{
+    text_color = "#333",
+    align = lvgl.ALIGN.CENTER,
+    text = "Test " .. (failed and "Failed" or "Success")
+}

examples/tests.lua

@@ -35,6 +35,7 @@ local function createBtn(parent, name)
 end
 
 createBtn(container, "gesture")
+createBtn(container, "objid")
 createBtn(container, "font")
 createBtn(container, "uservalue")
 createBtn(container, "roller")

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/lv_conf.h

@@ -303,7 +303,7 @@
 #define LV_USE_OBJ_ID           1
 
 /* Use lvgl builtin method for obj ID */
-#define LV_USE_OBJ_ID_BUILTIN   1
+#define LV_USE_OBJ_ID_BUILTIN   0
 
 /*Use obj property set/get API*/
 #define LV_USE_OBJ_PROPERTY 1

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.*/

src/obj.c

@@ -608,6 +608,33 @@ static int luavgl_obj_get_pos(lua_State *L)
   return 1;
 }
 
+static int luavgl_obj_get_child_by_id(lua_State *L)
+{
+  lv_obj_t *obj;
+  const char *id;
+  if (lua_type(L, 1) == LUA_TSTRING) {
+    obj = NULL;
+    id = lua_tostring(L, 1);
+  } else {
+    obj = luavgl_to_obj(L, 1);
+    id = luaL_checkstring(L, 2);
+  }
+
+  lv_obj_t *child = lv_obj_get_child_by_id(obj, id);
+  if (child == NULL) {
+    lua_pushnil(L);
+    return 1;
+  }
+
+  lua_pushlightuserdata(L, child);
+  lua_rawget(L, LUA_REGISTRYINDEX);
+  if (lua_isnil(L, -1)) {
+    luavgl_add_lobj(L, child)->lua_created = false;
+  }
+
+  return 1;
+}
+
 /**
  * Remove all animations associates to this object
  */
@@ -719,6 +746,52 @@ LUALIB_API int luavgl_obj_get_property(lua_State *L)
   return obj_property(L, obj);
 }
 
+#if LV_USE_OBJ_ID_BUILTIN == 0
+/* For luavgl, we only support string as ID. */
+void lv_obj_assign_id(const lv_obj_class_t *class_p, lv_obj_t *obj) {}
+
+void lv_obj_free_id(lv_obj_t *obj)
+{
+  if (obj->id) {
+    lv_free(obj->id);
+    obj->id = NULL;
+  }
+}
+
+const char *lv_obj_stringify_id(lv_obj_t *obj, char *buf, uint32_t len)
+{
+  if (obj->id == NULL)
+    return NULL;
+  lv_strlcpy(buf, (const char *)obj->id, len);
+  return buf;
+}
+
+int lv_obj_id_compare(const void *id1, const void *id2)
+{
+  if (id1 == NULL || id2 == NULL)
+    return -1;
+  return lv_strcmp(id1, id2);
+}
+
+#endif
+
+static int obj_property_id(lua_State *L, lv_obj_t *obj, bool set)
+{
+  if (set) {
+    if (!lua_isstring(L, -1)) {
+      return luaL_error(L, "id should be string");
+    }
+
+    lv_obj_set_id(obj, lv_strdup(lua_tostring(L, -1)));
+    return 0;
+  } else {
+    /* get property */
+    void *id = lv_obj_get_id(obj);
+    id == NULL ? lua_pushnil(L) : lua_pushstring(L, id);
+    return 1;
+  }
+}
+
 static int obj_property_align(lua_State *L, lv_obj_t *obj, bool set)
 {
   if (set) {
@@ -790,6 +863,7 @@ static int obj_property_user_data(lua_State *L, lv_obj_t *obj, bool set)
 
 static const luavgl_property_ops_t obj_property_ops[] = {
     {.name = "align",     .ops = obj_property_align    },
+    {.name = "id",        .ops = obj_property_id       },
     {.name = "h",         .ops = obj_property_h        },
     {.name = "w",         .ops = obj_property_w        },
     {.name = "user_data", .ops = obj_property_user_data},
@@ -844,6 +918,7 @@ static const rotable_Reg luavgl_obj_methods[] = {
     {"indev_search",             LUA_TFUNCTION,      {luavgl_obj_indev_search}            },
     {"get_coords",               LUA_TFUNCTION,      {luavgl_obj_get_coords}              },
     {"get_pos",                  LUA_TFUNCTION,      {luavgl_obj_get_pos}                 },
+    {"get_child_by_id",          LUA_TFUNCTION,      {luavgl_obj_get_child_by_id}         },
 
     {"onevent",                  LUA_TFUNCTION,      {luavgl_obj_on_event}                },
     {"onPressed",                LUA_TFUNCTION,      {luavgl_obj_on_pressed}              },
@@ -958,6 +1033,10 @@ static void luavgl_obj_init(lua_State *L)
   /* 3. Base lv_obj metatable */
   luavgl_obj_newmetatable(L, &lv_obj_class, "lv_obj", luavgl_obj_methods);
   lua_pop(L, 1); /* remove obj metatable */
+
+  /* Register to global function */
+  lua_pushcfunction(L, luavgl_obj_get_child_by_id);
+  lua_setfield(L, -2, "get_child_by_id");
 }
 
 /**