if (screenPt.x > 0.0f && screenPt.y > 0.0f && screenPt.x < window_w && screenPt.y < window_h) {
                        const float dx = history[iter].x - float(x);
                        const float dy = history[iter].y - float(y);
                        const double dist = double(500.0f * std::sqrt(dx*dx + dy * dy));
                        rolling_delta = std::min(rolling_delta, std::max(delta / (dist + 1e-5), delta_minimum*speed_mult));
                        isOffScreen = false;
                    }