Firing a bullet with SDL

[guestgulkan]

are your bullet and dot bitmaps loading ok.

Also - in GUI the Y co-ordinates go from TOP to BOTTOM .
so to go down then it is y+ and to go up it is y-

ps did you use the entire code I gave??

[Timbo1]

I have managed to now get the bullet to fire upwards when I press the space bar. I still have a few problems though. The bullet is always on top of the dot. when I move the dot the bullet doesn't move with it. How could I fix this. I messed up completely whilst trying to fix the second problem but it is back to normal now. :D

[Return 0]

The bullet is always on top of the dot. when I move the dot the bullet doesn't move with it

Well... which is it? Those sentences are contradictory.

[guestgulkan]

Because you paint them that way. Your order for screen painting is:

myDot.show();  
myBullet.show1();

So the dot is drawn first, then the bullet. So the bullet will overlay the dot if they are in the same position.

The dot and the bullet are independent entities. If you want them to move at the same time, you will have to move them at the same time.

[Timbo1]

Whenever I press space the bullet moves to the left:

Bullet::Bullet()
{
    //Initialize the velocity
    xVel1 = 0;
    yVel1 = 0;
    
    x1 = 11;
    y1 = 420;
}

void Bullet::handle_input1()
{
    //If a key was pressed
    if( event.type == SDL_KEYDOWN )
    {
        //Adjust the velocity
        switch( event.key.keysym.sym )
        {
                case SDLK_SPACE: yVel1 = 5;
            case SDLK_LEFT: xVel1 -= DOT_WIDTH / 3; break;
            case SDLK_RIGHT: xVel1 += DOT_WIDTH / 3; break;
        }
    }
     //If a key was released
     else if( event.type == SDL_KEYUP )
     {
        //Adjust the velocity
        switch( event.key.keysym.sym )
        {
                case SDLK_SPACE: yVel1 = 5;
            case SDLK_LEFT: xVel1 += DOT_WIDTH / 3; break;
            case SDLK_RIGHT: xVel1 -= DOT_WIDTH / 3; break;
        }
    }
    }

void Bullet::move1()
{
    //Move the dot up or down
    y1 -= yVel1;
    x1 += xVel1;
}

Please help

[guestgulkan]

break;

[Timbo1]

It is going up straight byut when I move left the bullet doesn't follow but stays in the same position.

void Bullet::handle_input1()
{
    //If a key was pressed
    if( event.type == SDL_KEYDOWN )
    {
        //Adjust the velocity
        switch( event.key.keysym.sym )
        {
            case SDLK_SPACE: yVel1 = 5;
            case SDLK_LEFT: xVel1 -= DOT_WIDTH / 3;
            case SDLK_RIGHT: xVel1 += DOT_WIDTH / 3;
        }
    }
     //If a key was released
     else if( event.type == SDL_KEYUP )
     {
        //Adjust the velocity
        switch( event.key.keysym.sym )
        {
            case SDLK_SPACE: yVel1 = 5;
            case SDLK_LEFT: xVel1 += DOT_WIDTH / 3; 
            case SDLK_RIGHT: xVel1 -= DOT_WIDTH / 3;
        }
    }
}



void Bullet::move1()
{
    //Move the dot up or down
    y1 -= yVel1;
    x1 += xVel1;
}

[Return 0]

You shouldn't even be blitting the bullet surface if it's not firing. When the space bar is pressed, the bullets starting x coord should be whatever the dots x coord is. Make sense?

[guestgulkan]

Oh Timbo1 - you really are hard work I'm sorry to say.
Do you you understand how switch and case statement work?


You are making this much harder than it needs to be.
Anyway - try this - note that the bullet is only on screen drueing the firing stage.
Return 0 mentioned this, but I hard already incorporated it.
((Notice I have removed most of your comments to make it fit in one post))

#include "SDL/SDL.h"
#include "SDL/SDL_image.h"

#include <string>

const int SCREEN_WIDTH = 640;
const int SCREEN_HEIGHT = 480;
const int SCREEN_BPP = 32;

const int FRAMES_PER_SECOND = 15;

const int DOT_WIDTH = 25;
const int DOT_HEIGHT = 42;

const int BULLET_WIDTH = 13;
const int BULLET_HEIGHT = 31;

SDL_Surface *dot = NULL;
SDL_Surface *screen = NULL;
SDL_Surface *bullet = NULL;

SDL_Event event;

    int x, y;
    
    int xVel1 = 0;
    int yVel1 = 3;

class Dot
{
    private:
    int xVel, yVel;
    public:
    Dot();

    void handle_input();
    void move();

    void show();
};

class Timer
{
    private:
    int startTicks;

    int pausedTicks;

    bool paused;
    bool started;

    public:
    Timer();

    void start();
    void stop();
    void pause();
    void unpause();

    int get_ticks();

    bool is_started();
    bool is_paused();
};

SDL_Surface *load_image( std::string filename )
{
    SDL_Surface* loadedImage = NULL;

    SDL_Surface* optimizedImage = NULL;

    loadedImage = IMG_Load( filename.c_str() );

    if( loadedImage != NULL )
    {
        optimizedImage = SDL_DisplayFormat( loadedImage );

        SDL_FreeSurface( loadedImage );

        if( optimizedImage != NULL )
        {
            SDL_SetColorKey( optimizedImage, SDL_SRCCOLORKEY, SDL_MapRGB( optimizedImage->format, 0, 0xFF, 0xFF ) );
        }
    }

    return optimizedImage;
}

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

    offset.x = x;
    offset.y = y;

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

bool init()
{
    if( SDL_Init( SDL_INIT_EVERYTHING ) == -1 )
    {
        return false;
    }

    screen = SDL_SetVideoMode( SCREEN_WIDTH, SCREEN_HEIGHT, SCREEN_BPP, SDL_SWSURFACE );
    if( screen == NULL )
    {
        return false;
    }

    SDL_WM_SetCaption( "Tank Game", NULL );

    return true;
}

bool load_files()
{
    dot = load_image( "dot.bmp" );
    if( dot == NULL )
    {
        return false;
    }
     bullet = load_image( "bullet.png" );
     
     if( bullet == NULL )
     {
         return false;
     }
     

    return true;
}

void clean_up()
{
    SDL_FreeSurface( dot );
    SDL_FreeSurface(bullet);

    //Quit SDL
    SDL_Quit();
}

Dot::Dot()
{
    x = 1;
    y = 420;

    xVel = 0;
    yVel = 0;
}

void Dot::handle_input()
{
    if( event.type == SDL_KEYDOWN )
    {
        switch( event.key.keysym.sym )
        {
            case SDLK_LEFT: xVel -= DOT_WIDTH / 3; break;
            case SDLK_RIGHT: xVel += DOT_WIDTH / 3; break;
        }
    }
    else if( event.type == SDL_KEYUP )
    {
        switch( event.key.keysym.sym )
        {
            case SDLK_LEFT: xVel += DOT_WIDTH / 3; break;
            case SDLK_RIGHT: xVel -= DOT_WIDTH / 3; break;
        }
    }
}

void Dot::move()
{
    x += xVel;

    if( ( x < 0 ) || ( x + DOT_WIDTH > SCREEN_WIDTH ) )
    {
        x -= xVel;
    }

    y += yVel;

    if( ( y < 0 ) || ( y + DOT_HEIGHT > SCREEN_HEIGHT ) )
    {
        y -= yVel;
    }
}

void Dot::show()
{
    apply_surface( x, y, dot, screen );
}

Timer::Timer()
{
    startTicks = 0;
    pausedTicks = 0;
    paused = false;
    started = false;
}

void Timer::start()
{
    started = true;

    paused = false;

    startTicks = SDL_GetTicks();
}

void Timer::stop()
{
    started = false;

    paused = false;
}

void Timer::pause()
{
    if( ( started == true ) && ( paused == false ) )
    {
        paused = true;

        pausedTicks = SDL_GetTicks() - startTicks;
    }
}

void Timer::unpause()
{
    if( paused == true )
    {
        paused = false;

        startTicks = SDL_GetTicks() - pausedTicks;

        pausedTicks = 0;
    }
}

int Timer::get_ticks()
{
    if( started == true )
    {
        if( paused == true )
        {
            return pausedTicks;
        }
        else
        {
            return SDL_GetTicks() - startTicks;
        }
    }

    return 0;
}

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

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

class Bullet
{
    private:
    //The X and Y offsets of the bullet
    int x1, y1;

    //The velocity of the bullet
    int xVel1, yVel1;

    public:
    Bullet();

    //Takes key presses and adjusts the bullet's velocity
    void handle_input1();

    //Moves the bullet
    void move1();

    //Shows the bullet on the screen
    void show1();

    bool isFired;
};

Bullet::Bullet()
{
    //Initialize the position and velocity
  x1 = 20;
  y1 = 400;
    xVel1 = 0;
    yVel1 = 3;

    isFired = false;
}

void Bullet::handle_input1()
{
    if( event.type == SDL_KEYDOWN )
    {
        //Adjust the velocity
        switch( event.key.keysym.sym )
        {
          case SDLK_SPACE: 
            if (isFired)
            {
               yVel1 = BULLET_HEIGHT / 3;
            }


              
            else //first firing
            {
              //move the bullet to the position of the dot
              x1=x;
              y1=y;
              yVel1 = 3;
              isFired = true;
            }
          break;

          default:
            break;


              
        }
    }
    //If a key was released
    else if( event.type == SDL_KEYUP )
    {
        //Adjust the velocity
        switch( event.key.keysym.sym )
        {
            case SDLK_SPACE: 
              if (isFired)
              {
                yVel1 = 3;
              }
                break;
            default:
              break;

        }
    }
}

void Bullet::move1()
{
    //Only move Move the bullet if fired
      if (isFired)
      {
        y1 -= yVel1;
      }
}

void Bullet::show1()
{
  //Only show the bullet if fired and it is onscreen
  if (isFired && y1+BULLET_HEIGHT >0)
  {
    apply_surface( x1, y1, bullet, screen );
  }
  else
  {
    isFired = false;
  }


}



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

    Dot myDot;
    Bullet myBullet;

    Timer fps;

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

    if( load_files() == false )
    {
        return 1;
    }

   
        while( quit == false )
    {
        fps.start();

        while( SDL_PollEvent( &event ) )
        {
            //Handle events for the dot and bullet
            myDot.handle_input();
            myBullet.handle_input1();

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

           //Fill the screen green
        SDL_FillRect( screen, &screen->clip_rect, SDL_MapRGB( screen->format, 0x7F, 0xFF, 0x00 ) );

        myDot.show();
        myBullet.show1();
      
        //Move the dot and bullet
        myDot.move();
        myBullet.move1();



        //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;
}