SFML RenderWindow pops up late if i ask for user input

Question

So i am trying to make a sorting algorithms visualizer with SFML. It is all good until i ask user input for the size of the array and which algorithm user wants to see it visualized. When i ask for user input, program executes in the background for a bit, sorting starts but i cant display it for couple of seconds.

int main(){

    int Size = takeSize();
    int choice = takeAlgorithm();
    fillArray(Size);

    while(window.isOpen()){

        Event event;

        while (window.pollEvent(event))
            if(event.type == Event::Closed) window.close();    

        if(!sorted){
            dispSort(0);
            algorithmSelector(choice);
        }

    }
    return 0;
}

Here is my main program. Everything works perfectly if i set the size of the array and which sorting algorithm will run before, but if i take input from user with takeSize() and takeAlgorithm() functions:

int takeSize(){

    cout << "Please enter a number between 10 and 150 for the number of elements in the array: \n";
    int vectorSize;
    while(true){
        cin >> vectorSize;
        if(vectorSize >=10 && vectorSize <=199)
            return vectorSize;
        else{
            cout << "Please enter a valid number between the given ranges!\n";
            continue;
        }
    }
}

int takeAlgorithm(){

    cout << "Please enter the corresponding number to select the sorting algorithm you want to see visualized: \n";
    cout << "1-) Bubble Sort\n";
    cout << "2-) Merge Sort\n";
    cout << "3-) Insertion Sort\n";
    cout << "4-) Selection Sort\n";
    cout << "5-) Gnome Sort\n";

    int number;
    cin >> number;
    return number;

}

Window displays late while sorting starts in the background. Note: i use this in global scope -> RenderWindow window(VideoMode(601, 600), "Sorting Algorithm Visualizer!"); So an empty window shows up, then i enter the inputs after that window goes to the background.

Answer 1

The problem is that an SFML window doesn't display unless you poll for events so it won't show just because you constructed sf::RenderWindow. Your code takes a while to reach the point when you poll for events because std::cin blocks SFML.

Your options are to not use std::cin and instead get keyboard input using SFML in a GUI or you can accept that the window won't open before an array size is entered. I think the latter actually makes more sense because it's not clear what your window would display if there isn't an array of elements to sort.