Continuous stutter

[naezith]

I have a stutter issue that I couldn't fix trying everything for 2.5 years. It is not always happening but like %75 of the time I have stutter. When it's gone, game runs ultra smooth.

Here I recorded it, I thought it wouldn't be visible in camera because of low FPS but it is clearly visible. It looks like a thick pillar moving to right in the video because of the FPS but you will see that sometimes it snaps to left for a moment, that's the stutter. Screenshot of the snap moment.

Here are the stuff I tried.

• VSync On/Off does not matter
• FPS 60-2000 does not matter

Here is the minimal code:

#include <SFML/Graphics.hpp>
#include <chrono>

using namespace std::chrono_literals;

int main() {
	sf::RenderWindow window(sf::VideoMode(1280, 720), "Stutter");
	sf::Event event;

	const float dt = 0.008f;
    std::chrono::nanoseconds timestep(8ms), lag(0ns);
    auto time_start = std::chrono::high_resolution_clock::now();

	sf::RectangleShape rect(sf::Vector2f(5.0f, 720.0f));
	float pos = 0.0f, prev_pos = 0.0f, org_pos = 0.0f;

	while(window.isOpen()) {
        // Calculate the elapsed time and add it to lag
        auto now = std::chrono::high_resolution_clock::now();
		lag += now - time_start;
        time_start = now;

		while(lag >= timestep) {
			lag -= timestep;

			// Save the previous value
			prev_pos = pos;

			// Poll Events
			while(window.pollEvent(event)) if(event.type == sf::Event::Closed) window.close();

			// Update
			if((pos += 1000.0f*dt) > 1280.0f) { prev_pos = org_pos = pos = 0.0f; }
		}


		// Save the original value before drawing
		org_pos = pos;

		// Interpolate
		pos = prev_pos + (static_cast<double>(lag.count()) / timestep.count()) * (pos - prev_pos);

		// Set position to interpolated position
		rect.setPosition(pos, 0.0f);

		// Render
		window.clear();
		window.draw(rect);
		window.display();

		// Recover the original value
		pos = org_pos;
	}

	return 0;
}

---

ASUS VG248QE Monitor @144 hz <- Game runs on this
I also have another basic 19" LCD monitor plugged to the motherboard's Intel

SFML 2.4.1
MinGW 5.3.0 (x86_64-posix-seh-rev0, Built by MinGW-W64 project)
Windows 10, updated
GTX 770, updated
i7 i3770k

[naezith]

Updated SFML, joystick update fixed it.

It was caused by the joystick polling.