luavgl: add a method to focus an object

lib/luavgl/src/lvgl.lua

@@ -814,6 +814,11 @@ end
 function obj:invalidate()
 end
 
+--- Sets this object as the current selection of the object's group.
+---@return nil
+function obj:focus()
+end
+
 ---
 --- Object event callback. `para` is not used for now.
 --- @alias EventCallback fun(obj:Object, code: ObjEventCode): nil

lib/luavgl/src/obj.c

@@ -1,3 +1,5 @@
+#include "core/lv_group.h"
+#include "core/lv_obj.h"
 #include "luavgl.h"
 #include "private.h"
 
@@ -578,6 +580,21 @@ static int luavgl_obj_get_pos(lua_State *L) {
   return 1;
 }
 
+/**
+ * set this object as the current selection
+ */
+static int luavgl_obj_focus(lua_State *L) {
+  lv_obj_t *obj = luavgl_to_obj(L, 1);
+
+  lv_group_t *group = lv_obj_get_group(obj);
+  if (group == NULL) {
+    return 0;
+  }
+  lv_group_focus_obj(obj);
+
+  return 0;
+}
+
 /**
  * Remove all animations associates to this object
  */
@@ -654,6 +671,7 @@ static const luaL_Reg luavgl_obj_methods[] = {
     {"indev_search", luavgl_obj_indev_search},
     {"get_coords", luavgl_obj_get_coords},
     {"get_pos", luavgl_obj_get_pos},
+    {"focus", luavgl_obj_focus},
 
     {"onevent", luavgl_obj_on_event},
     {"onPressed", luavgl_obj_on_pressed},