C++ console game input && refresh function

Question

Hello, I am writing a small console adventure game and I faced a few problems.
1. The input is kinda laggy, I'm using while loop ( while(getch() == 'w') ). After a key is pressed the first time, nothing happens (you have to press it 2 times) and if you switch directions (press key A/D/S) it also doesn't react the 1st time. If you hold a key, it works fine. How can this be fixed?
2. Here's the function I use to refresh game (render the game scene when a key is pressed):

    void refresh(char map[Y][X])
{
    system("cls");
    for (int i = 0; i<UP; i++)
    {
        cout<<endl;
    }
    for (int i = 0; i<Y; i++)
    {
        for (int k = 0; k<LEFT; k++)
        {
            cout<<" ";
        }
        for (int j = 0; j<X; j++)
        {
            cout<<map[i][j];
        }
        cout<<endl;
    }
}

When I use this function once, it's ok, but when they key is pressed or held multiple times - the game field starts to flash. I figured that I need to redraw only a part of the field (where changes are made/movements are done), not the whole field. Can you offer any ideas how to do that?

The sample code for input:

while(getch() == 'w')
    {
        if (map[y-1][x]!= WALL)
        {
        map[y-1][x] = CHARACTER;
        map [y][x] = ' ';
        y--;
        refresh(map);
        Sleep(SPEED); // this is unnecessary, SPEED is 0, I just kept it for tests
        }
    }

Basically, the main function looks like this:

int main()
{
    (...) Variables (...)
    generateMap(FROM FILE);
    refresh(); // First initialization of the field
    while (getch() != 'q') // While not quitting
    {
    while(getch() == 'w')
    {
        if (THE FIELD ABOVE IS NOT OCCUPIED)
        {
             setSomeVariables();
             refresh(THE GAMEFIELD);
        }
    }
    }
    while(getch() == 's')
    {
        if (THE FIELD BELOW IS NOT OCCUPIED)
        {
             setSomeVariables();
             refresh(THE GAMEFIELD);
        }
    }
    }
    while(getch() == 'a')
    {
        if (THE FIELD ON THE LEFT IS NOT OCCUPIED)
        {
             setSomeVariables();
             refresh(THE GAMEFIELD);
        }
    }
    }
    while(getch() == 'd')
    {
        if (THE FIELD ON THE RIGHT IS NOT OCCUPIED)
        {
             setSomeVariables();
             refresh(THE GAMEFIELD);
        }
    }
    }
    return 0;
}

Answer 1

1. The code should have only one getch() in the whole code (if possible) and inside a switch you do the action for each input. So, it is switch inside the loop, and not loops inside the switch. Something like this:

   while ((ch = getch()) != 'q') { switch (ch) { case 'a': GoLeft(); break; ... } }

2. There is a library called ncurses that you can use to move the cursor around the screen, and write anything anywhere.

Answer 2

Why do you have so many loops? I'm not fimiliar with your code style, but surely its slow because of so many loops. Cant you use IF's instead?

Answer 3

Don't use system("cls"), it is really slow, instead set the cursor on the beginning of the screen with the following code:

COORD cur = {0, 0};
SetConsoleCursorPosition(GetStdHandle(STD_OUTPUT_HANDLE), cur);

You should call getch() only one time in the loop, like this:

char key;

do
{
    key = getch();

    if(key == 'w')
    {
        //do something
    }

    //the other if statements

}while(key != 'q');

Answer 4

It looks like your problem is calling getch() multiple times. Have only one loop, and call getch() once per loop, and store the result. Test that result for each value (q, w, s, ...) for each iteration of the loop.