Hello Huy
Indeed, using default setting, the TTF file located in FGLDIR will not be cached. This is more convenient for development. While setting GAS and your application for production you need to take care that TTF files (as any other image files) is in the public image area (see
http://4js.com/online_documentation/fjs-gas-manual-html/#gas-topics/c_gas_deployment_public_images.html) so that they are cache-able.
Did you take care of that ?
Olivier.