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Firing a bullet with SDL

Pages: 12
Timbo1 (91)
I am trying something out with this sdl code but I get this error.

In member function `void Bullet::show1()':
cannot convert `SDL_Surface*' to `SDL_Rect*' for argument `5' to `void apply_surface(int, int, SDL_Surface*, SDL_Surface*, SDL_Rect*)' 

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void Bullet::show1()
{
    apply_surface( x, y, dot, screen, bullet );
}


If you need anymore code just tell me.

Also when I try taking out the x and the y because that was the obvious error I get about twenty other errors.

Please Help

Look down a few posts
Last edited on
Return 0 (1282)
I need to see your apply surface function.
Timbo1 (91)
I have got rid of the error but I need to make the bullet fire and I can't get it to work

Be warned it is quite long

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

//The 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 = 15;

//The dimensions of the dot
const int DOT_WIDTH = 25;
const int DOT_HEIGHT = 42;

//The dimensions of the bullet
const int BULLET_WIDTH = 13;
const int BULLET_HEIGHT = 31;

//The surfaces
SDL_Surface *dot = NULL;
SDL_Surface *screen = NULL;
SDL_Surface *bullet = NULL;

//The event structure
SDL_Event event;

//The X and Y offsets of the dot
    int x, y;

//The dot that will move around on the screen
class Dot
{
    private:
    //The velocity of the dot
    int xVel, yVel;

    public:
    
    //Initializes the variables
    Dot();

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

    //Moves the dot
    void move();

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

//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 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( "Tank Game", NULL );

    //If everything initialized fine
    return true;
}

bool load_files()
{
     //load the bullet
     bullet = load_image( "bullet.bmp" );
     
     //if there was a problem loading the dot
     if( bullet == NULL )
     {
         return false;
     }
     
    //Load the dot image
    dot = load_image( "dot.bmp" );

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

    //If everything loaded fine
    return true;
}

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

    //Quit SDL
    SDL_Quit();
}

Dot::Dot()
{
    //Initialize the offsets
    x = 1;
    y = 420;

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

void Dot::handle_input()
{
    //If a key was pressed
    if( event.type == SDL_KEYDOWN )
    {
        //Adjust the velocity
        switch( event.key.keysym.sym )
        {
            case SDLK_LEFT: xVel -= DOT_WIDTH / 3; break;
            case SDLK_RIGHT: xVel += 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_LEFT: xVel += DOT_WIDTH / 3; break;
            case SDLK_RIGHT: xVel -= DOT_WIDTH / 3; break;
        }
    }
}

void Dot::move()
{
    //Move the dot left or right
    x += xVel;

    //If the dot went too far to the left or right
    if( ( x < 0 ) || ( x + DOT_WIDTH > SCREEN_WIDTH ) )
    {
        //move back
        x -= xVel;
    }

    //Move the dot up or down
    y += yVel;

    //If the dot went too far up or down
    if( ( y < 0 ) || ( y + DOT_HEIGHT > SCREEN_HEIGHT ) )
    {
        //move back
        y -= yVel;
    }
}

void Dot::show()
{
    //Show the dot
    apply_surface( x, y, dot, 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;
}
Timbo1 (91)
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bool Timer::is_started()
{
    return started;
}

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

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

    //The dot that will be used
    Dot myDot;

    //The frame rate regulator
    Timer fps;

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

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

    //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 dot
            myDot.handle_input();

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

        //Move the dot
        myDot.move();

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

        //Show the dot on the screen
        myDot.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;
}

//The bullet that will move on the screen
class Bullet
{
    private:
    //The X and Y offsets of the dot
    int x1, y1;

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

    public:
    //Initializes the variables
    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();
};

Bullet::Bullet()
{
    //Initialize the velocity
    xVel1 = 0;
    yVel1 = 3;
}

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 += BULLET_HEIGHT / 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 -= BULLET_HEIGHT / 3; break;
        }
    }
}

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

void Bullet::show1()
{
    //Show the dot
    apply_surface( x, y, screen, bullet );
}
Return 0 (1282)
I don't see you creating an instance of bullet anywhere or calling its member functions in your game loop.
Timbo1 (91)
explain please I am a beginner to SDL.
Return 0 (1282)
I see you've created a Bullet class and it's methods. You need to start by creating a bullet object just as you created a dot object here:

Dot myDot;

You've written code to animate the bullet (I haven't checked it), but you can't call that code until you initialize a bullet.

Bullet myBullet;

You can then call myBullet.whatever() when a specific button is pressed. I'm assuming you want to make the bullet fire across the screen, but what determines which direction the bullet should fire in?

You should also break out your classes into separate interface and implementation files.
Timbo1 (91)
Then I get this error after I edited all the code

In function `int SDL_main(int, char**)':
Bullet' undeclared (first use this function)
Return 0 (1282)
I'm assuming you didn't break out the classes into separate header files. According to the code you've posted, your Bullet class is placed below your main function. When it reaches Bullet myBullet; it doesn't know what Bullet is. Move the class above main with your dot and timer classes.
Timbo1 (91)
First of all the bullet still isn't shooting and this is my code. How would I break it up. I have never done that before.

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

//The 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 = 15;

//The dimensions of the dot
const int DOT_WIDTH = 25;
const int DOT_HEIGHT = 42;

//The dimensions of the bullet
const int BULLET_WIDTH = 13;
const int BULLET_HEIGHT = 31;

//The surfaces
SDL_Surface *dot = NULL;
SDL_Surface *screen = NULL;
SDL_Surface *bullet = NULL;

//The event structure
SDL_Event event;

//The X and Y offsets of the dot
    int x, y;
    
    //Initialize the velocity
    int xVel1 = 0;
    int yVel1 = 3;

//The dot that will move around on the screen
class Dot
{
    private:
    //The velocity of the dot
    int xVel, yVel;

    public:
    
    //Initializes the variables
    Dot();

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

    //Moves the dot
    void move();

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

//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 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( "Tank Game", NULL );

    //If everything initialized fine
    return true;
}

bool load_files()
{
     //load the bullet
     bullet = load_image( "bullet.bmp" );
     
     //if there was a problem loading the dot
     if( bullet == NULL )
     {
         return false;
     }
     
    //Load the dot image
    dot = load_image( "dot.bmp" );

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

    //If everything loaded fine
    return true;
}

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

    //Quit SDL
    SDL_Quit();
}

Dot::Dot()
{
    //Initialize the offsets
    x = 1;
    y = 420;

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

void Dot::handle_input()
{
    //If a key was pressed
    if( event.type == SDL_KEYDOWN )
    {
        //Adjust the velocity
        switch( event.key.keysym.sym )
        {
            case SDLK_LEFT: xVel -= DOT_WIDTH / 3; break;
            case SDLK_RIGHT: xVel += 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_LEFT: xVel += DOT_WIDTH / 3; break;
            case SDLK_RIGHT: xVel -= DOT_WIDTH / 3; break;
        }
    }
}

void Dot::move()
{
    //Move the dot left or right
    x += xVel;

    //If the dot went too far to the left or right
    if( ( x < 0 ) || ( x + DOT_WIDTH > SCREEN_WIDTH ) )
    {
        //move back
        x -= xVel;
    }

    //Move the dot up or down
    y += yVel;

    //If the dot went too far up or down
    if( ( y < 0 ) || ( y + DOT_HEIGHT > SCREEN_HEIGHT ) )
    {
        //move back
        y -= yVel;
    }
}

void Dot::show()
{
    //Show the dot
    apply_surface( x, y, dot, 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;
}

//The bullet that will move on the screen
class Bullet
{
    private:
    //The X and Y offsets of the dot
    int x1, y1;

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

    public:
    //Initializes the variables
    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();
};

Bullet::Bullet()
{
    //Initialize the velocity
    xVel1 = 0;
    yVel1 = 3;
}

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 += BULLET_HEIGHT / 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 -= BULLET_HEIGHT / 3; break;
        }
    }
}

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

void Bullet::show1()
{
    //Show the dot
    apply_surface( x, y, screen, bullet );
}




Timbo1 (91)
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int main( int argc, char* args[] )
{
    //Quit flag
    bool quit = false;

    //The dot that will be used
    Dot myDot;
    
    //The bullet that will be used
    Bullet myBullet;

    //The frame rate regulator
    Timer fps;

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

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

    //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 dot
            myDot.handle_input();
            myBullet.handle_input1();

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

        //Move the dot
        myDot.move();
        
        myBullet.move1();

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

        //Show the dot on the screen
        myDot.show();
        
        myBullet.show1();

        //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;
}
Timbo1 (91)
Please help guys. The bullet isn't shooting. or showing at all. How do I make it fire?
Return 0 (1282)
In order to display several objects moving on the screen at once (aside from using multithreading) you're going to need a game state setup so that you can easily draw the locations of every object on the screen to simulate movement. To get you started here's what you're going to need:

Dot object. You have this, from looking at your code, I guess the only direction the bullet will fire is from left to right considering you can only move the dot left to right... which makes this easy. Now when you hit the space bar... or whatever key binding you desire, the bullet will need to fire from the x,y coordinate where the dot resides to make it look like its firing out of the dot. In order to have the bullet move across the screen, every frame you will need to grab the x,y coordinates of the bullet and each time it is drawn you're basically increasing its location on the x axis.

In order to avoid flickering screen movement you will need to use a technique called double buffering. Essentially you will have the following structs:

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


Right now you are blitting everything to the screen. Which means that the system will go one by one and apply the surfaces to the screen. You will need to apply dot & bullet to the buffer and apply the buffer to the screen, so you are basically going to apply the locations of all the objects as one image and then call SDL_Flip(screen);.

Hope this helps.
Timbo1 (91)
The bullet will be firing up like in a space invaders game. I have changed the SDL_Surfaces to what you have but I am still confused as to what I do next.
guestgulkan (2942)
This function is wrong:
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void Bullet::show1()
{
    //Show the dot
    apply_surface( x, y, screen, bullet ); //CHECK THE ORDER OF YOUR PARAMETERS!!
}


Another problem is that you are using the same x,y co-ordinates for the dot and the bullet?
You should be using x1 and y1 for the bullet??

I know you cut and pasted the some of the code between dt and bullet - but the comments
have not been updated.
Last edited on
Timbo1 (91)
If I put them in any other order I get an error. Can you just explain very plainly what I have to do to get the bullet I have tried to set up fire from the bottom to the top.
Return 0 (1282)
guestgulkan is not referring to the order of the arguments. You are passing x and y which are not the members of the Bullet class. You should be passing x1, y1 which is the Bullets coordinates.
guestgulkan (2942)
Try this:
It is a simple correction your code and should show something happening - it works for me.
The bullet goes from top to bottom - I haven't amended that part of your code.

In two parts:
Part 1 - the main part
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int main( int argc, char* args[] )
{
    //Quit flag
    bool quit = false;

    //The dot that will be used
    Dot myDot;
    
    //The bullet that will be used
    Bullet myBullet;

    //The frame rate regulator
    Timer fps;

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

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

    //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 dot
            myDot.handle_input();
                  myBullet.handle_input1();

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

        //Move the dot
        myDot.move();
        
        myBullet.move1();

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

        //Show the dot on the screen
        myDot.show();
        
        myBullet.show1();

        //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;
}


guestgulkan (2942)
Part 2 - the other bits
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//The headers
#include "SDL/SDL.h"
#include "SDL/SDL_image.h"
#include <string>

//The 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 = 15;

//The dimensions of the dot
const int DOT_WIDTH = 25;
const int DOT_HEIGHT = 42;

//The dimensions of the bullet
const int BULLET_WIDTH = 13;
const int BULLET_HEIGHT = 31;

//The surfaces
SDL_Surface *dot = NULL;
SDL_Surface *screen = NULL;
SDL_Surface *bullet = NULL;

//The event structure
SDL_Event event;

//The X and Y offsets of the dot
    int x, y;
    
    //Initialize the velocity
    int xVel1 = 0;
    int yVel1 = 3;

//The dot that will move around on the screen
class Dot
{
    private:
    //The velocity of the dot
    int xVel, yVel;

    public:
    
    //Initializes the variables
    Dot();

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

    //Moves the dot
    void move();

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

//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 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( "Tank Game", NULL );

    //If everything initialized fine
    return true;
}

bool load_files()
{
     //load the bullet
     bullet = load_image( "bullet.bmp" );
     
     //if there was a problem loading the bullet
     if( bullet == NULL )
     {
         return false;
     }
     
    //Load the dot image
    dot = load_image( "dot.bmp" );

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

    //If everything loaded fine
    return true;
}

void clean_up()
{
    //Free the surface
    SDL_FreeSurface( dot );
    SDL_FreeSurface(bullet);

    //Quit SDL
    SDL_Quit();
}

Dot::Dot()
{
    //Initialize the offsets
    x = 1;
    y = 420;

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

void Dot::handle_input()
{
    //If a key was pressed
    if( event.type == SDL_KEYDOWN )
    {
        //Adjust the velocity
        switch( event.key.keysym.sym )
        {
            case SDLK_LEFT: xVel -= DOT_WIDTH / 3; break;
            case SDLK_RIGHT: xVel += 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_LEFT: xVel += DOT_WIDTH / 3; break;
            case SDLK_RIGHT: xVel -= DOT_WIDTH / 3; break;
        }
    }
}

void Dot::move()
{
    //Move the dot left or right
    x += xVel;

    //If the dot went too far to the left or right
    if( ( x < 0 ) || ( x + DOT_WIDTH > SCREEN_WIDTH ) )
    {
        //move back
        x -= xVel;
    }

    //Move the dot up or down
    y += yVel;

    //If the dot went too far up or down
    if( ( y < 0 ) || ( y + DOT_HEIGHT > SCREEN_HEIGHT ) )
    {
        //move back
        y -= yVel;
    }
}

void Dot::show()
{
    //Show the dot
    apply_surface( x, y, dot, 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;
}

//The bullet that will move on the screen
class Bullet
{
    private:
    //The X and Y offsets of the dot
    int x1, y1;

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

    public:
    //Initializes the variables
    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();
};

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

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 += BULLET_HEIGHT / 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 -= BULLET_HEIGHT / 3; break;
        }
    }
}

void Bullet::move1()
{
    //Move the bullet up or down
    y1 += yVel1;
}

void Bullet::show1()
{
    //Show the bullet
    apply_surface( x1, y1, bullet, screen );
}
Timbo1 (91)
With your version the window flashes then disappears. I need it to go from bottom to top and even when I change it to x1 and y1 it still doesn't work.
Last edited on
Pages: 12