pub fn tick(&mut self) -> bool {
        if self.offset.elapsed() >= self.period {
            self.offset += self.period;
            true
        } else {
            false
        }
    }
/// clock tick
/// return true if a clock period has elapsed. otherwise, return false
clock tick
return true if a clock period has elapsed. otherwise, return false
clock tick return true if a clock period has elapsed . otherwise return false
pub fn tick(&mut self) -> bool {
        if self.offset.elapsed() >= self.period {
            self.offset += self.period;
            true
        } else {
            false
        }
    }
pub fn tick ( & mut self ) -> bool { if self . offset . elapsed ( ) >= self . period { self . offset += self . period ; true } else { false } }
clock tick
return true if a clock period has elapsed.
clock tick return true if a clock period has elapsed .
&mut self
&mut self