Problem with drawGame function in a Snake Game

Question

I'm programming a Snake Game in C++ in order to learn more about C ++. I made the game using the paradigms of object-oriented programming, but the design of the drawGame function is not working properly.

Testing the drawGame function, I'm getting this as result:

void Game::drawGame(int fruitxpos, int fruitypos, std::vector<int>& xposition, std::vector<int>& yposition, int snakesize){
    system("cls");
    int printedflag = 0;
    for(int j = 1; j <= ysize; j++){
        if(j == 1 || j == ysize){
            for(int i = 1; i <= xsize; i++){
                std::cout << "#";
            }
            std::cout << "\n";
        }       
        else{
            for(int i = 1; i <= xsize; i++){
                if(i == 1 || i == xsize){
                    std::cout << "#";
                }
                else{
                    for(int n = 0; n <= snakesize; n++){
                        if(i == xposition[n] && j == yposition[n]){
                            std::cout << "o";
                            printedflag = 1;
                        }
                        else{
                            printedflag = 0; 
                        }
                    }
                    if(!printedflag){
                        if(i == fruitxpos && j == fruitypos){
                            std::cout << "F";
                        }
                        else{
                            std::cout << " ";
                        }
                    }   
                }
            }
            std::cout << "\n";
        }
    }
}

As you can see, It is printing a blank space after every snake block. Could someone explain me what is wrong?

Hi, welcome to Stack Overflow. Have you tried stepping through your code with a debugger? That's an essential programmer skill, and would probably give you the answer faster than typing up the question here. — Angew is no longer proud of SO, Jul 16 '19 at 18:57
What he said ^. On the rare chance that a debugger didn't come with the compiler, strongly consider switching compilers. — user4581301, Jul 16 '19 at 18:57
Answer below shook another comment loose: C++ IO streams are a poor choice for doing work like this because they're streams and output like this doesn't make a good stream. Consider using a [terminal library like ncurses](https://en.wikipedia.org/wiki/Ncurses) and taking advantage of writing over stuff you want cleared "Dirty Rectangle" style. — user4581301, Jul 16 '19 at 19:15
@user4581301 If you draw into a matrix of characters, you can then use the C++ I/O streams with no problems, especially if an extra column is added for newlines and the last matrix cell is '\0'. — Thomas Matthews, Jul 16 '19 at 19:32
@ThomasMatthews Yes, but then you have to put up with the old screen content being pushed up off the top of the screen by the new content or go outside Standard C++ to do a screen clear (and probably get a flickering problem). — user4581301, Jul 16 '19 at 19:51

Thomas Matthews · Answer 1 · 2019-07-16T19:56:11.783

IMHO, your program would be better by using a 2d matrix of characters. Your main program will write into the matrix. A print function would print the matrix. This eliminates the worry of having to use X,Y positioning on the console.

If you design the matrix as a {contiguous} array of characters, you can add an extra column for the newline character. The last cell of the matrix would be the nul character, '\0'. This allows you to print the matrix as if it was one long C-Style string.

Some example code:

const unsigned int MAX_COLUMNS = 20U + 1U; // +1 column for newline
const unsigned int MAX_ROWS    = 20U;
char game_board[MAX_ROWS][MAX_COLUMNS];

void Clear_Board()
{
    // Fill the board with spaces (blanks).
    memset((char *) &game_board[0][0], ' ', sizeof(game_board));

    // Draw the top and bottom borders
    for (unsigned int column = 0; column < MAX_COLUMNS; ++column)
    {
        game_board[0][column] = '#';
        game_board[MAX_ROWS - 1][column] = '#';
    }

    // Draw the side borders
    const unsigned int LEFT_COLUMN = 0U;
    const unsigned int RIGHT_COLUMN = MAX_COLUMNS - 2U;
    const unsigned int NEWLINE_COLUMN = MAX_COLUMNS - 1U;
    for (unsigned int row = 0; row < MAX_ROWS; ++row)
    {
        game_board[row][LEFT_COLUMN] = '#';
        game_board[row][RIGHT_COLUMN] = '#';
        game_board[row][NEWLINE_COLUMN] = '\n';
    }

    // Set the terminating nul character
    game_board[MAX_ROWS - 1][MAX_COLUMNS - 1] = '\0';
}

Printing the board:

std::cout << game_board;

or

std::cout.write(&game_board[0][0], sizeof(game_board) - 1U); // Don't print terminating nul.

Checking for fruit encounter

unsigned int snake_head_row = 10U;    // Example position.
unsigned int snake_head_column = 5u;  
const char FRUIT_CHAR = 'F';
//...
if (game_board[snake_head_row][snake_head_column] == FRUIT_CHAR)
{
  //...
}

Notice that the fruit encounter doesn't need printing.

IMHO, you should have the snake as a container of coordinates (row, column). Each body cell is an item in the container. If the snake grows, append a coordinate to the container. Drawing the snake involves traversing the container, placing snake characters at the appropriate game_board positions (then drawing the board).

A game board helps remember the position of the snake body and any other items on the board. You can use a console positioning library and put the characters at their coordinates, too.

score -1 · Answer 2 · answered Jul 16 '19 at 19:07

-1

Suggesting to split your Game::drawGame into sub-functions. Also, probably the method should not get all the parameters you pass to it as they all should better be class members.

void Game::drawGame() {
    drawBoard();
    drawSnake();
    drawFruits();
}

Then you may want to use gotoxy that can be found on the web, e.g. here, e.g. for windows:

void gotoxy(int x, int y) {
    HANDLE hc = GetStdHandle(STD_OUTPUT_HANDLE);  // get console handle 
    COORD cursor = { x, y };
    SetConsoleCursorPosition(hc, cursor);  // set new cursor position
}

answered Jul 16 '19 at 19:07

Amir Kirsh

12,564
41
74

1

What makes you think the OP is using Windows? – Angew is no longer proud of SO Jul 16 '19 at 19:10
The ncurses library will eliminate portability issues. – user4581301 Jul 16 '19 at 19:12
Except ncurses is not supported natively by windows. You must use cygwin, MSYS2, or some other similar environment. – Scott Mudge Jul 16 '19 at 19:23
No, it's not native, but there are available libraries, even for Visual Studio. I shouldn't have called out ncurses specifically and stayed with the more generic curses. – user4581301 Jul 16 '19 at 19:55
@ScottMudge There exist multiple Windows ports of ncurses. – Jesper Juhl Jul 16 '19 at 20:12
There are two: PDCurses and the GNUWin32 project, but they are not direct ports, and neither are completely compatible with ncurses, and are therefore not an ideal portable solution. It would be better to use a completely portable, header-based solution like 'rlutil' https://tapiov.net/rlutil/ – Scott Mudge Jul 16 '19 at 20:26

Problem with drawGame function in a Snake Game

2 Answers2

Some example code:

Printing the board:

Checking for fruit encounter