// Handle keyboard events
void GLUTkey(unsigned char k, int x, int y);
void GLUTkeyup(unsigned char k, int x, int y);
void GLUTspecialkey(int k, int x, int y);
void GLUTspecialkeyup(int k, int x, int y);
// Handle keyboard events
void GLUTkey(unsigned char k, int x, int y);
void GLUTkeyup(unsigned char k, int x, int y);
void GLUTspecialkey(int k, int x, int y);
void GLUTspecialkeyup(int k, int x, int y);