@hansim
in the this lib file , you can find the str width return function:
https://github.com/m5stack/M5Stack/blob/master/src/utility/In_eSPI.h
int16_t textWidth(const char *string, uint8_t font),
textWidth(const char *string),
textWidth(const String& string, uint8_t font),
textWidth(const String& string),
fontHeight(int16_t font),
fontHeight(void);