While thing

Hi!

I'm making a game, just to learn SDL. But i seem to have some trouble with my code. If i cpoy and paste my code from the while into the switch it works. It is the same code. But if i do like that, the piece wouldn't move if you hold down the button. It would only move when you press the button.

How can i make this work?

Code:

---

    //While the user hasn't quit
    while( quit == false )
    { 
        //If there's an event to handle
        if( SDL_PollEvent( &event ) )
        {
            //If a key was pressed
            if( event.type == SDL_KEYDOWN )
            {
                //Set the proper holder surface
                switch( event.key.keysym.sym )
                {                     
                    case SDLK_LEFT:
                        left = true;
                        break;
                       
                    case SDLK_RIGHT:
                        right = true;
                        break;
                       
                    case SDLK_ESCAPE:
                        quit = true;
                        break;   
                }
            }
           
            //Check if the right is pressed
            while (right == true)
            {
                        x = x + 10;
                        SDL_FillRect( screen, NULL, NULL );
                        apply_surface( 0, 0, background, screen );
                        piece = load_image( "piece-right.png" );
                        apply_surface( x, y, piece, screen );
            }
           
            //Check if the left is pressed
            while (left == true)
            {
                        x = x - 10;
                        SDL_FillRect( screen, NULL, NULL );
                        apply_surface( 0, 0, background, screen );
                        piece = load_image( "piece-left.png" );
                        apply_surface( x, y, piece, screen );
            }
           
            }   
            //If the user has Xed out the window
            else if( event.type == SDL_QUIT )
            {
                //Quit the program
                quit = true;
            }
   
        //Update the screen
        if( SDL_Flip( screen ) == -1 )
        {
            return 1;   
        }
    }

---

Consider this: why would "left" or "right" change while you're in the loops?

Hmm... I didn't thought of that. That was a very good question. My answer is: I don't know! :) Do you have a suggestion?

Change them to if, not while

No, cause if i do that. It would only happen 1 time. You see?

No - leave the outer while as while
Change the inner ones to if
See?

No i don't understand. :s Explain :)

Or maybe you mean limke this?

Code:

---

while (left = true)
{
          if (left == true)
          {
          }
}

---

But if you mean like that, we still have the same problem. :p

EDIT:
You're right! If i add right = false; or left = false; to the while loop everything goes well.
But we still have the same problem. Holding the key doesn't work!

If i recall correctly, SDL only signals when keys are pressed or released. If you want to check if a key is *held down* for a longer time, you'd have to do it manually by also checking for KEYUP events. I'm too busy right now to dust off my SDL-fu and write an example, sorry.

Okey, meanwhile i wait for you to write an example, i'll search on internet.

> if( event.type == SDL_KEYDOWN )
There's also key up event as well I assume?

What about timer events? Do you (or can you) get a regular timer event as well?

On key down, set the flag and move in the required direction.
On key up, clear the flag
On timer, if the flag is set then also do a move.

What do you mean with timer? Never heard of it.

EDIT:

Tried like you said, with keyup. Didn't work.

Code:

---

    //While the user hasn't quit
    while( quit == false )
    { 
        //If there's an event to handle
        if( SDL_PollEvent( &event ) )
        {
            //If a key was pressed
            if( event.type == SDL_KEYDOWN )
            {
                //Set the proper holder surface
                switch( event.key.keysym.sym )
                {                     
                    case SDLK_LEFT:
                        left = true;
                        break;
                       
                    case SDLK_RIGHT:
                        right = true;
                        break;
                       
                    case SDLK_ESCAPE:
                        quit = true;
                        break;   
                }
            }
           
            //If a key was released
            if( event.type == SDL_KEYUP )
            {
                //Set the proper holder surface
                switch( event.key.keysym.sym )
                {                     
                    case SDLK_LEFT:
                        left = false;
                        break;
                       
                    case SDLK_RIGHT:
                        right = false;
                        break; 
                }
            }
           
            //Check if the right is pressed
            while (right == true)
            {
                        x = x + 10;
                        SDL_FillRect( screen, NULL, NULL );
                        apply_surface( 0, 0, background, screen );
                        piece = load_image( "piece-right.png" );
                        apply_surface( x, y, piece, screen );
            }
           
            //Check if the left is pressed
            while (left == true)
            {
                        x = x - 10;
                        SDL_FillRect( screen, NULL, NULL );
                        apply_surface( 0, 0, background, screen );
                        piece = load_image( "piece-left.png" );
                        apply_surface( x, y, piece, screen );
            }
           
            }   
            //If the user has Xed out the window
            else if( event.type == SDL_QUIT )
            {
                //Quit the program
                quit = true;
            }
   
        //Update the screen
        if( SDL_Flip( screen ) == -1 )
        {
            return 1;   
        }
    }

---

It's going to be hard to write anything, if you don't at least read something first.

Go and read (or at least skim slowly) all the SDL material you have on hand at the moment.
Something which takes a good few hours, not bouncing it straight back in 10 minutes.

But i want the game to work. This is the way im learning stuff. Doing it first, so i know how they work. And after that, i read about them. But if you know somewhere hey have KEYUP or something like that, tell me!

Here's the first thing that popped up when I typed "SDL KEYUP" in google:
http://gpwiki.org/index.php/SDL:Tuto...Keyboard_Input

> This is the way im learning stuff. Doing it first, so i know how they work. And after that, i read about them.

I think you might benefit from switching up the paradigm a little bit.

Well, actuallt i learn better from first testing, then reading. It's a fact.

I played around with your link but didn't get it to work. You can see my whole main-function here:

Code:

---

int main( int argc, char* args[] )
{
    //The pieces coordinates
    int x = 200;
    int y = 200;
   
    //Left flag
    bool left = false;
   
    //Right flag
    bool right = false;
   
    //Quit flag
    bool quit = false;
   
    //Initialize
    if( init() == false )
    {
        return 1;
    }
   
    //Load the files
    if( load_files() == false )
    {
        return 1;
    }
   
    //Apply the background
    apply_surface( 0, 0, background, screen );
   
    //Apply the piece
    apply_surface( 70, 178, piece, screen );
   
    //While the user hasn't quit
    while( quit == false )
    { 
        //If there's an event to handle
        while (SDL_PollEvent(&event))
        {
              if (event.type == SDL_KEYDOWN)
              {
                                switch(event.key.keysym.sym)
                                {
                                                              case SDLK_LEFT:
                                                                    left = true;
                                                                    break;
                                                                   
                                                              case SDLK_RIGHT:
                                                                    right = true;
                                                                    break;
                                                                   
                                                              case SDLK_ESCAPE:
                                                                    quit = true;
                                                                    break;
              }                }
             
              if (event.type == SDL_KEYUP)
              {
                                switch(event.key.keysym.sym)
                                {
                                                                case SDLK_LEFT:
                                                                      left = false;
                                                                      break;
                                                               
                                                                case SDLK_RIGHT:
                                                                    right = false;
                                                                    break;
                                }
              }     
            //Check if the right is pressed
            while (right == true)
            {
                        x = x + 10;
                        SDL_FillRect( screen, NULL, NULL );
                        apply_surface( 0, 0, background, screen );
                        piece = load_image( "piece-right.png" );
                        apply_surface( x, y, piece, screen );
            }
           
            //Check if the left is pressed
            while (left == true)
            {
                        x = x - 10;
                        SDL_FillRect( screen, NULL, NULL );
                        apply_surface( 0, 0, background, screen );
                        piece = load_image( "piece-left.png" );
                        apply_surface( x, y, piece, screen );
            }
           
            }   
            //If the user has Xed out the window
            if( event.type == SDL_QUIT )
            {
                //Quit the program
                quit = true;
            }
   
        //Update the screen
        if( SDL_Flip( screen ) == -1 )
        {
            return 1;   
        }
    }
       
       
    //Clean up
    clean_up();
   
    return 0;   
}

---

> while (right == true)
Like has been said already.

If right is false, if never gets into the loop.
If right is true, it never gets out of the loop.

Roughly speaking (5 mins reading the manual), I would try
- SDL_AddTimer to set a timer.
- In the timer callback function, call SDL_PushEvent to send a 'user' event, which in this context will mean that time has elapsed.

Replace the while (right == true) with if (right == true)
You'll now be getting periodic stimulus of the event queue (through the timer).

I'm not good at english. I don't really understand what you're saying. Show me some code.
EDIT:
What manual? :o

This is hard :p

Quote:

---

Originally Posted by Livijn

But i want the game to work.

---

Everybody wants their stuff to work.

So why should you succeed in getting it to work? You need to put the effort into it. Playing around with tests is fine if you know what you're doing, but you have to be willing to invest in reading up on the library you're using.

> What manual?
The one from http://www.libsdl.org/docs.php
I mean, c'mon - this isn't rocket science.

Quote:

---

Originally Posted by Salem

I mean, c'mon - this isn't rocket science.

---

That would be ironic if his game involves spaceships. :D

You know, if you say the title of this thread quickly it sounds sort of like this. </offtopic>

Lol, now it works when i'm moving the mouse. So if i hold down left button without moving the mouse, the piece goes 1 way to the left. If i move the mouse all the time the piece moves exactly like i want it to do without moving the mouse.

Understand?

Please don't bump threads to get them moved up on the list. If someone has some help to offer, they'll post. Until then, keep working on the problem yourself.

Okey! But i am working on it. I've been for the whole day. :( Only breaks for food and fresh air, which is together something like 2h.

>> Okey! But i am working on it. I've been for the whole day.
Just keep at it. One piece at a time. Break it down as much as you can to narrow down the problem. Good luck.

I almsot got it now! When i move the mouse and hold down left or right, it moves! I think it is because the mouse gives the program a new event. Right? So if i would like to do this without moving the mouse. How should i do?

Code:

Code:

---

    //While the user hasn't quit
    while( quit == false )
    { 
        //If there's an event to handle
        while (SDL_PollEvent(&event))
        {
              if (event.type == SDL_KEYDOWN)
              {
                                switch(event.key.keysym.sym)
                                {
                                                              case SDLK_LEFT:
                                                                    left = true;
                                                                    break;
                                                                   
                                                              case SDLK_RIGHT:
                                                                    right = true;
                                                                    break;
                                                                   
                                                              case SDLK_ESCAPE:
                                                                    quit = true;
                                                                    break;
              }                }
             
              if (event.type == SDL_KEYUP)
              {
                                switch(event.key.keysym.sym)
                                {
                                                                case SDLK_LEFT:
                                                                      left = false;
                                                                      SDL_FillRect( screen, NULL, NULL );
                                                                      apply_surface( 0, 0, background, screen );
                                                                      piece = load_image( "piece.png" );
                                                                      apply_surface( x, y, piece, screen );
                                                                      break;
                                                               
                                                                case SDLK_RIGHT:
                                                                    right = false;
                                                                    SDL_FillRect( screen, NULL, NULL );
                                                                    apply_surface( 0, 0, background, screen );
                                                                    piece = load_image( "piece.png" );
                                                                    apply_surface( x, y, piece, screen );
                                                                    break;
                                }
              }     
            //Check if the right is pressed
            if (right == true)
            {
                        x = x + 1;
                        SDL_FillRect( screen, NULL, NULL );
                        apply_surface( 0, 0, background, screen );
                        piece = load_image( "piece-right.png" );
                        apply_surface( x, y, piece, screen );
            }
           
            //Check if the left is pressed
            if (left == true)
            {
                        x = x - 1;
                        SDL_FillRect( screen, NULL, NULL );
                        apply_surface( 0, 0, background, screen );
                        piece = load_image( "piece-left.png" );
                        apply_surface( x, y, piece, screen );
            }
           
            //Apply the square
            apply_surface( 400, 150, square, screen );
           
            }   
            //If the user has Xed out the window
            if( event.type == SDL_QUIT )
            {
                //Quit the program
                quit = true;
            }
   
        //Update the screen
        if( SDL_Flip( screen ) == -1 )
        {
            return 1;   
        }
    }

---

Bump :(

Put the if(right == true) (by the way, why don't you simply use if(right) ?) outside the while(SDL_PollEvent...)

Thank you!!!!!!1111oneoneone