nanogui: Thread: error compiling flnx-0.15

Hi,
If I try to compile flnx-0.15, there is error message on:
"GR_MODIFIER_CTRL" undeclared (first use this function)
"GR_MODIFIER_SHIFT" undeclared (first use this function)
"GR_MODIFIER_LOCK" undeclared (first use this function)
"GR_MODIFIER_NUMLOCK" undeclared (first use this function)
"GR_MODIFIER_META" undeclared (first use this function)
"GR_MODIFIER_SCROLLLOCK" undeclared (first use this function)

Is there anything I forget to do??

thanks