please help with pong game

**corndogg** · 02-18-2013

please help, I am trying to build a pong game but the collision detection is only working for one paddle and I cannot get the paddles to move, here is my code

Code:

//The headers
#include "SDL/SDL.h"
#include "SDL/SDL_image.h"
#include <string>

//Screen attributes
const int SCREEN_WIDTH = 640;
const int SCREEN_HEIGHT = 480;
const int SCREEN_BPP = 32;

//The frame rate
const int FRAMES_PER_SECOND = 20;

//The attributes of the square
const int SQUARE_WIDTH = 20;
const int SQUARE_HEIGHT = 20;
const int WALL_HEIGHT = 20;

//The surfaces
SDL_Surface *square = NULL;
SDL_Surface *screen = NULL;

//The event structure
SDL_Event event;

//The wall
SDL_Rect wall;
SDL_Rect wall2;
//The square
class Square
{
    private:
    //The collision box of the square
    SDL_Rect box;

    //The velocity of the square
    int xVel, yVel;

    public:
    //Initializes the variables
    Square();

    //Takes key presses and adjusts the square's velocity
    void handle_input();

    //Moves the square
    void move();

    //Shows the square on the screen
    void show();
};

//The square
class Wall
{
    private:
    //The collision box of the wall
    SDL_Rect box;

    //The velocity of the wall
    int xVel, yVel;

    public:
    //Initializes the variables
    Wall();

    //Takes key presses and adjusts the walls velocity
    void handle_input2();

    //moves the wall
    void move2();

    

   
};


//The timer
class Timer
{
    private:
    //The clock time when the timer started
    int startTicks;

    //The ticks stored when the timer was paused
    int pausedTicks;

    //The timer status
    bool paused;
    bool started;

    public:
    //Initializes variables
    Timer();

    //The various clock actions
    void start();
    void stop();
    void pause();
    void unpause();

    //Gets the timer's time
    int get_ticks();

    //Checks the status of the timer
    bool is_started();
    bool is_paused();
};

SDL_Surface *load_image( std::string filename )
{
    //The image that's loaded
    SDL_Surface* loadedImage = NULL;

    //The optimized surface that will be used
    SDL_Surface* optimizedImage = NULL;

    //Load the image
    loadedImage = IMG_Load( filename.c_str() );

    //If the image loaded
    if( loadedImage != NULL )
    {
        //Create an optimized surface
        optimizedImage = SDL_DisplayFormat( loadedImage );

        //Free the old surface
        SDL_FreeSurface( loadedImage );

        //If the surface was optimized
        if( optimizedImage != NULL )
        {
            //Color key surface
            SDL_SetColorKey( optimizedImage, SDL_SRCCOLORKEY, SDL_MapRGB( optimizedImage->format, 0, 0xFF, 0xFF ) );
        }
    }

    //Return the optimized surface
    return optimizedImage;
}

void apply_surface( int x, int y, SDL_Surface* source, SDL_Surface* destination, SDL_Rect* clip = NULL )
{
    //Holds offsets
    SDL_Rect offset;

    //Get offsets
    offset.x = x;
    offset.y = y;

    //Blit
    SDL_BlitSurface( source, clip, destination, &offset );
}

bool check_collision( SDL_Rect A, SDL_Rect B )
{
    //The sides of the rectangles
    int leftA, leftB;
    int rightA, rightB;
    int topA, topB;
    int bottomA, bottomB;

    //Calculate the sides of rect A
    leftA = A.x;
    rightA = A.x + A.w;
    topA = A.y;
    bottomA = A.y + A.h;

    //Calculate the sides of rect B
    leftB = B.x;
    rightB = B.x + B.w;
    topB = B.y;
    bottomB = B.y + B.h;

    //If any of the sides from A are outside of B
    if( bottomA <= topB )
    {
        return false;
    }

    if( topA >= bottomB )
    {
        return false;
    }

    if( rightA <= leftB )
    {
        return false;
    }

    if( leftA >= rightB )
    {
        return false;
    }

    //If none of the sides from A are outside B
    return true;
}

bool check_collision2( SDL_Rect B, SDL_Rect C )
{
    //The sides of the rectangles
    int leftB, leftC;
    int rightB, rightC;
    int topB, topC;
    int bottomB, bottomC;

    //Calculate the sides of rect A
    leftB = B.x;
    rightB = B.x + B.w;
    topB = B.y;
    bottomB = B.y + B.h;

    //calculate the side or rect C
    leftC = C.x;
    rightC = C.x + C.w;
    topC = C.y;
    bottomC = C.y + C.h; 

  

//If any of the sides from A are outside of C
    if( bottomB <= topC )
    {
        return false;
    }

    if( topB >= bottomC )
    {
        return false;
    }

    if( rightB <= leftC )
    {
        return false;
    }

    if( leftB >= rightC )
    {
        return false;
    }

     //If none of the sides from A are outside B
    return true;
}

bool init()
{
    //Initialize all SDL subsystems
    if( SDL_Init( SDL_INIT_EVERYTHING ) == -1 )
    {
        return false;
    }

    //Set up the screen
    screen = SDL_SetVideoMode( SCREEN_WIDTH, SCREEN_HEIGHT, SCREEN_BPP, SDL_SWSURFACE );

    //If there was an error in setting up the screen
    if( screen == NULL )
    {
        return false;
    }

    //Set the window caption
    SDL_WM_SetCaption( "Move the Square", NULL );

    //If everything initialized fine
    return true;
}

bool load_files()
{
    //Load the square image
    square = load_image( "square.bmp" );

    //If there was a problem in loading the square
    if( square == NULL )
    {
        return false;
    }

    //If everything loaded fine
    return true;
}

void clean_up()
{
    //Free the surface
    SDL_FreeSurface( square );

    //Quit SDL
    SDL_Quit();
}

Square::Square()
{
    //Initialize the offsets
    box.x = 0;
    box.y = 0;
   

    //Set the square's dimentions
    box.w = SQUARE_WIDTH;
    box.h = SQUARE_HEIGHT;
    


    //Initialize the velocity
    xVel = 0;
    yVel = 0;
}

    Wall::Wall()
{
    wall.x = 0;
    wall.y = 0;

    wall.h = WALL_HEIGHT;
    

    xVel = 0;
    yVel = 0;
}
void Square::handle_input()
{
    //If a key was pressed
    if( event.type == SDL_KEYDOWN )
    {
        //Adjust the velocity
        switch( event.key.keysym.sym )
        {
            case SDLK_UP: yVel -= SQUARE_HEIGHT / 2; break;
            case SDLK_DOWN: yVel += SQUARE_HEIGHT / 2; break;
            case SDLK_LEFT: xVel -= SQUARE_WIDTH / 2; break;
            case SDLK_RIGHT: xVel += SQUARE_WIDTH / 2; break;
        }
    }
    //If a key was released
    else if( event.type == SDL_KEYUP )
    {
        //Adjust the velocity
        switch( event.key.keysym.sym )
        {
            case SDLK_UP: yVel += SQUARE_HEIGHT / 2; break;
            case SDLK_DOWN: yVel -= SQUARE_HEIGHT / 2; break;
            case SDLK_LEFT: xVel += SQUARE_WIDTH / 2; break;
            case SDLK_RIGHT: xVel -= SQUARE_WIDTH / 2; break;
        }
    }
}

void Wall::handle_input2()
{
    //If a key was pressed
    if( event.type == SDL_KEYDOWN )
    {
        //Adjust the velocity
        switch( event.key.keysym.sym )
        {
            case SDLK_w: yVel -= WALL_HEIGHT / 2; break;
            case SDLK_z: yVel += WALL_HEIGHT / 2; break;
         
        }
    }
    //If a key was released
    else if( event.type == SDL_KEYUP )
    {
        //Adjust the velocity
        switch( event.key.keysym.sym )
        {
            case SDLK_w: yVel += WALL_HEIGHT / 2; break;
            case SDLK_z: yVel -= WALL_HEIGHT / 2; break;
         
        }
    }
}
void Square::move()
{
    //Move the square left or right
    box.x += xVel;

    //If the square went too far to the left or right or has collided with the wall
    if( ( box.x < 0 ) || ( box.x + SQUARE_WIDTH > SCREEN_WIDTH ) || ( check_collision( box, wall ) ) )
    {
        //Move back
        box.x -= xVel;
    }

    //Move the square up or down
    box.y += yVel;

    //If the square went too far up or down or has collided with the wall
    if( ( box.y < 0 ) || ( box.y + SQUARE_HEIGHT > SCREEN_HEIGHT ) || ( check_collision( box, wall ) ) )
    {
        //Move back
        box.y -= yVel;
    }

}

void Wall::move2()
{
  
    //Move the square up or down
    wall.y += yVel;

    //If the square went too far up or down or has collided with the wall
    if( ( wall.y < 0 ) || ( wall.y + WALL_HEIGHT > SCREEN_HEIGHT ) || ( check_collision2( box, wall ) ) )
    {
        //Move back
        wall.y -= yVel;
    }

}


void Square::show()
{
    //Show the square
    apply_surface( box.x, box.y, square, screen );
}

void Wall::show2()
{
    //Show the square
    apply_surface( box.x, box.y, square, screen );
}


Timer::Timer()
{
    //Initialize the variables
    startTicks = 0;
    pausedTicks = 0;
    paused = false;
    started = false;
}

void Timer::start()
{
    //Start the timer
    started = true;

    //Unpause the timer
    paused = false;

    //Get the current clock time
    startTicks = SDL_GetTicks();
}

void Timer::stop()
{
    //Stop the timer
    started = false;

    //Unpause the timer
    paused = false;
}

void Timer::pause()
{
    //If the timer is running and isn't already paused
    if( ( started == true ) && ( paused == false ) )
    {
        //Pause the timer
        paused = true;

        //Calculate the paused ticks
        pausedTicks = SDL_GetTicks() - startTicks;
    }
}

void Timer::unpause()
{
    //If the timer is paused
    if( paused == true )
    {
        //Unpause the timer
        paused = false;

        //Reset the starting ticks
        startTicks = SDL_GetTicks() - pausedTicks;

        //Reset the paused ticks
        pausedTicks = 0;
    }
}

int Timer::get_ticks()
{
    //If the timer is running
    if( started == true )
    {
        //If the timer is paused
        if( paused == true )
        {
            //Return the number of ticks when the timer was paused
            return pausedTicks;
        }
        else
        {
            //Return the current time minus the start time
            return SDL_GetTicks() - startTicks;
        }
    }

    //If the timer isn't running
    return 0;
}

bool Timer::is_started()
{
    return started;
}

bool Timer::is_paused()
{
    return paused;
}

int main( int argc, char* args[] )
{
    //Quit flag
    bool quit = false;

    //The square
    Square mySquare;

    //The square
   Wall myWall;


    //The frame rate regulator
    Timer fps;

    //Initialize
    if( init() == false )
    {
        return 1;
    }

    //Load the files
    if( load_files() == false )
    {
        return 1;
    }

    //Set the wall
    wall.x = 600;
    wall.y = 200;
    wall.w = 20;
    wall.h = 100;

    //Set the wall
    wall2.x = 20;
    wall2.y = 200;
    wall2.w = 20;
    wall2.h = 100;

   

    //While the user hasn't quit
    while( quit == false )
    {
        //Start the frame timer
        fps.start();

        //While there's events to handle
        while( SDL_PollEvent( &event ) )
        {
            //Handle events for the square
            mySquare.handle_input();

            //If the user has Xed out the window
            if( event.type == SDL_QUIT )
            {
                //Quit the program
                quit = true;
            }
        }

        //Move the square
        mySquare.move();

        //Move the square
        myWall.move2();

        //Fill the screen white
        SDL_FillRect( screen, &screen->clip_rect, SDL_MapRGB( screen->format, 0xFF, 0xFF, 0xFF ) );

        //Show the wall
        SDL_FillRect( screen, &wall, SDL_MapRGB( screen->format, 0x77, 0x77, 0x77 ) );

    //Show the wall
        SDL_FillRect( screen, &wall2, SDL_MapRGB( screen->format, 0x77, 0x77, 0x77 ) );


        //Show the square on the screen
        mySquare.show();

        //Update the screen
        if( SDL_Flip( screen ) == -1 )
        {
            return 1;
        }

        //Cap the frame rate
        if( fps.get_ticks() < 1000 / FRAMES_PER_SECOND )
        {
            SDL_Delay( ( 1000 / FRAMES_PER_SECOND ) - fps.get_ticks() );
        }
    }

    //Clean up
    clean_up();

    return 0;
}

thanks in advance

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