RenderWindow Constantly Updating display() Causing Flickering - c++

Question

I am trying to write a program which allows users to draw using the mouse. I have been trying many different ways to appropriately update the display using an object of sf::RenderWindow to call display() without much success. My loop where the drawing is occurring is calling display so fast it's causing massive flickering (confirmed that through testing). If I add a way to slow the call to display(), like using sf::Clock, then the drawing is only updated on the same delay as display() resulting in a stuttering effect. What I need is a way to update the display often enough to show drawing updates while also not causing a screen flicker.
Currently, I've got the display on a delay (at the bottom of the event polling switch statement) so flickering doesn't occur, but adding mainWindow.display(); to the void MainWindow::draw() function causes flickering as it updates too quickly. I had the drawing occurring on sf::Event::MouseMoved, but I tried changing it to see if that would help, and it did not.
Here's where all the drawing and event detection occurs:
MainWindow.h
#pragma once
#include "GraphPaper.h"
#include "stdafx.h"
class MainWindow
{
public:
MainWindow(short, short);
void close();
void start();
void moveCamera(sf::Keyboard::Key);
void draw(sf::Event);
void displayWindow(sf::Vector2i&);
private:
bool leftMousePressed, rightMousePressed, isExiting;
int r, g, b, mouseX, mouseY;
short height, width;
const short DRAWING_CRICLE_RADIUS = 10;
GraphPaper paper;
//DrawingBrush brush;
const sf::Color WHITE = sf::Color(255, 255, 255);
const sf::Color BLACK = sf::Color(0, 0, 0);
sf::CircleShape circle;
sf::Mouse cursor;
sf::Vector2i windowCenter;
sf::RenderWindow mainWindow;
sf::View view;
};
MainWindow.cpp:
#include "MainWindow.h"
#include "GraphPaper.h"
#include "stdafx.h"
MainWindow::MainWindow(short height, short width)
{
this->height = height;
this->width = width;
circle.setRadius(DRAWING_CRICLE_RADIUS);
circle.setFillColor(BLACK);
}
void MainWindow::start()
{
sf::Clock clock;
mainWindow.create(sf::VideoMode(height, width, 32), "Test");
sf::View view(sf::FloatRect(0,0,height,width));
mainWindow.setView(view);
leftMousePressed, rightMousePressed, isExiting = false;
sf::Event currentEvent;
sf::Vector2i windowCenter(mainWindow.getPosition().x + (mainWindow.getSize().x / 2), mainWindow.getPosition().y + (mainWindow.getSize().y / 2));
displayWindow(windowCenter);
while (!isExiting)
{
sf::Clock clock;
while (mainWindow.pollEvent(currentEvent))
{
switch (currentEvent.type)
{
case sf::Event::MouseMoved:
{
if (rightMousePressed == true)
{
std::cout << "Mouse Panned\n";
}
if (leftMousePressed == true)
{
draw(currentEvent);
}
break;
}
case sf::Event::MouseButtonPressed:
{
std::cout << "Mouse Pressed\n";
mouseX = currentEvent.mouseButton.x;
mouseY = currentEvent.mouseButton.y;
if (currentEvent.mouseButton.button == sf::Mouse::Left)
{
while (currentEvent.type != sf::Event::MouseButtonReleased)
{
std::cout << "Mouse is Drawing\n";
draw(currentEvent);
mainWindow.pollEvent(currentEvent);
}
}
else if (currentEvent.mouseButton.button == sf::Mouse::Right)
{
rightMousePressed = true;
}
break;
}
case sf::Event::MouseButtonReleased:
{
std::cout << "Mouse Released\n";
if (currentEvent.mouseButton.button == sf::Mouse::Left)
{
leftMousePressed = false;
}
else if(currentEvent.mouseButton.button == sf::Mouse::Right)
{
rightMousePressed = false;
}
break;
}
case sf::Event::KeyPressed:
{
sf::Keyboard::Key keyPressed = currentEvent.key.code;
if(keyPressed == sf::Keyboard::Escape)
{
close();
}
else if(keyPressed == sf::Keyboard::Left || sf::Keyboard::Right ||
sf::Keyboard::Down || sf::Keyboard::Up ||
sf::Keyboard::A || sf::Keyboard::S ||
sf::Keyboard::D || sf::Keyboard::W)
{
moveCamera(keyPressed);
displayWindow(windowCenter);
}
break;
}
case sf::Event::Closed:
{
close();
break;
}
case sf::Event::Resized:
{
windowCenter = sf::Vector2i(mainWindow.getPosition().x + (mainWindow.getSize().x / 2), mainWindow.getPosition().y + (mainWindow.getSize().y / 2));
displayWindow(windowCenter);
break;
}
}
if (clock.getElapsedTime().asMilliseconds() >= 500)
{
clock.restart();
mainWindow.display();
}
}
}
}
void MainWindow::moveCamera(sf::Keyboard::Key keyPressed)
{
view = mainWindow.getView();
switch (keyPressed)
{
case sf::Keyboard::A:
case sf::Keyboard::Left:
{
view.move(-50, 0);
break;
}
case sf::Keyboard::D:
case sf::Keyboard::Right:
{
view.move(50, 0);
break;
}
case sf::Keyboard::W:
case sf::Keyboard::Up:
{
view.move(0, 50);
break;
}
case sf::Keyboard::S:
case sf::Keyboard::Down:
{
view.move(0, -50);
break;
}
}
mainWindow.setView(view);
}
void MainWindow::draw(sf::Event mouse)
{
circle.setPosition(mainWindow.mapPixelToCoords(sf::Vector2i(mouse.mouseMove.x, mouse.mouseMove.y)));
mainWindow.draw(circle);
}
void MainWindow::close()
{
std::cout << "Closing...\n";
mainWindow.close();
isExiting = true;
}
void MainWindow::displayWindow(sf::Vector2i& windowCenter)
{
mainWindow.clear(WHITE);
mainWindow.draw(paper.getSprite());
mainWindow.display();
cursor.setPosition(windowCenter);
}

Answer 1

You are missing an important part of the rendering loop. You should draw all parts every loop iteration. Right now you are only drawing your circle when it's changed.
Your code should look like this:
change circle position based on input
clear window
draw circle
display