-const std::string TEXT_FIT_ENABLE_KEY("enable");
-const std::string TEXT_FIT_MIN_SIZE_KEY("minSize");
-const std::string TEXT_FIT_MAX_SIZE_KEY("maxSize");
-const std::string TEXT_FIT_STEP_SIZE_KEY("stepSize");
-const std::string TEXT_FIT_FONT_SIZE_KEY("fontSize");
-const std::string TEXT_FIT_FONT_SIZE_TYPE_KEY("fontSizeType");
+const char* TEXT_FIT_ENABLE_KEY("enable");
+const char* TEXT_FIT_MIN_SIZE_KEY("minSize");
+const char* TEXT_FIT_MAX_SIZE_KEY("maxSize");
+const char* TEXT_FIT_STEP_SIZE_KEY("stepSize");
+const char* TEXT_FIT_FONT_SIZE_KEY("fontSize");
+const char* TEXT_FIT_FONT_SIZE_TYPE_KEY("fontSizeType");