RPGDXThe center of Indie-RPG gaming
Not logged in. [log in] [register]
faq search members
 
DevX, Are you there?
RPGDX >> Forums >> Design and programming >> DevX, Are you there?
 
Post new topic Reply to topic  
View previous topic - View next topic  
Author Message
Captain Vimes
Grumble Teddy


Joined: 12 May 2006
Posts: 225
Location: The City Streets
PostPosted: Fri Apr 20, 2007 5:26 pm    Post subject: DevX, Are you there? [quote]
Because I need help again.

WARNING MASSIVE CODAGE WARNING

Code:
//This is the basic SDL sprite-movement program
//SDLbasicmove
#include <SDL>
#include <stdio>

//The sprite's x and y velocity and position
int xPos = 562, yPos = 384;
int xVel = 0, yVel = 0;

int DetermineEventType(SDL_Event event)
{
    //This function returns an integer value corresponding to the type of event passed
    //through SDL_Event event.
    if(event.type == SDL_KEYDOWN)
    {
        //A key has been pressed
        return 0;
    }
    else if(event.type == SDL_KEYUP)
    {
        //A key has been released
        return 1;
    }
    else if(event.type == SDL_QUIT)
    {
         //Time to quit
         return 2;
    }
   
    //This should never happen, but just in case
    return 3;
}

void HandleKeyPress(SDL_KeyboardEvent key)
{
     //Handle the key presses
     switch(key.keysym.sym)
     {
     case SDLK_LEFT:
          xVel = -1;
          break;
     case SDLK_RIGHT:
          xVel = 1;
          break;
     case SDLK_UP:
          yVel = -1;
          break;
     case SDLK_DOWN:
          yVel = 1;
          break;
     }
     
     return;
}

void HandleKeyRelease(SDL_KeyboardEvent key)
{
     //Handle the key releases
     switch(key.keysym.sym)
     {
     case SDLK_LEFT:
          if(xVel <0> 0)
          {
                  xVel = 0;
          }
          break;
     case SDLK_UP:
          if(xVel <0> 0)
          {
                  yVel = 0;
          }
          break;
     }
     
     return;
}

int main(int argc, char* argv[])
{
    //Initialize the SDL video subsystem
    SDL_Init(SDL_INIT_VIDEO);
   
    //Create the screen surface
    SDL_Surface* pScreen = SDL_SetVideoMode(800, 600, 0, SDL_ANYFORMAT);
   
    //Create the character sprite surface
    SDL_Surface* pSprite = SDL_LoadBMP("sprite.bmp");
   
    //Set the sprite bitmap to use pink (255, 0, 255) as a transparent color
    SDL_SetColorKey(pSprite, SDL_SRCCOLORKEY, SDL_MapRGB(pScreen->format, 255, 0, 255));
   
    //The source and destination rects
    SDL_Rect srcRect, dstRect;
    srcRect.w = pSprite->w;
    srcRect.h = pSprite->h;
    srcRect.x = 0;
    srcRect.y = 0;
    dstRect = srcRect;
   
    //The event storage
    SDL_Event event;
   
    //Start the message pump
    for(;;)
    {
           //Check for the type of message
           int iMsgType = DetermineEventType(event);
           
           //Handle the message
           switch(iMsgType)
           {
           case 0:
                //The key has been pressed
                HandleKeyPress(event.key);
           case 1:
                //The key has been released
                HandleKeyRelease(event.key);
           case 2:
                //The program is quitting
                SDL_Quit();
                return 0;
           case 3:
                //There was an error
                printf("Error alert.");
                SDL_Quit();
                return 0;
           }
           
           //Clear the screen
           SDL_FillRect(pScreen, NULL, 0);
           
           //Place the sprite
           SDL_BlitSurface(pSprite, &srcRect, pScreen, &dstRect);
           
           //Move the sprite
           xPos += xVel;
           yPos += yVel;
           
           //Update the screen
           SDL_UpdateRect (pScreen, 0, 0, 0, 0);
    } //End the pump
   
    SDL_Quit();
    return 0;
}


Sorry about the massive codage, but I need help... the window appears for a split-second but then exits out, and that's after I seriously messed with it and placed all the key handlers in separate functions. Before it just didn't move the sprite.

HEEEEEEEEEEEEEEEAAAAAAAAAAAAAAALLLLLLLP








Are you ready?! 3 2 1 GO!

*launches into uber-hard mode Elite Beat Agents to the tune of Walkie-Talkie Man*

I have driven myself insane trying to figure out what this is. The function-separation was the last thing I tried.
_________________
"Sometimes it is better to light a flamethrower than to curse the darkness."
- Terry Pratchett
Back to top  
Scrim
Mandrake's Little Slap Bitch


Joined: 05 Apr 2007
Posts: 69
Location: Canada
PostPosted: Fri Apr 20, 2007 5:59 pm    Post subject: [quote]
I'm not an SDL expert, but if your program is dying a moment after it starts to run, that might mean the problem is not in your event handling code but actually in the SDL initialization. Are you sure it's correct? Perhaps your "sprite.bmp" file isn't loading properly or something similar.

You can always try the old trick of putting printf("Made it here!") at various stages in your code to determine how far it is getting before it dies.

Likewise, if it is initializing properly, you can then figure out if the problems is in your main loop or in one of the functions.
Back to top  
Rainer Deyke
Demon Hunter


Joined: 05 Jun 2002
Posts: 672
PostPosted: Fri Apr 20, 2007 6:04 pm    Post subject: [quote]
Several problems with this code:
  • You are including "SDL" and "stdio". The correct headers are "SDL.h" and either "cstdio" (in C++) or "stdio.h" (in C).
  • You are not actually reading events anywhere. Use SDL_PollEvent or SDL_WaitEvent.
  • You are using numeric literals when you should be using named constants. Instead of 0, use SDL_KEYDOWN. Instead of 1, use SDL_KEYUP. Instead of 2, use SDL_QUIT.
  • You are not handling some important event types, such as SDL_ACTIVEEVENT and SDL_MOUSEMOTION. It is OK to ignore these events, but they are not errors and should not be treated as such.
  • Your key release handler is badly broken. You are not handling the relase of SDLK_RIGHT or SDLK_DOWN, and "xVel <0> 0" is almost certainly not what you meant.
  • You don't have any timing code, so your sprite will move at different speeds on different computers.
  • You are missing the error checking on SDL_Init, SDL_SetVideoMode, and SDL_LoadBMP.
  • You are not converting the sprite into the pixel format of the screen. This is bad for performance, but more importantly, it means that you should not use the screen pixel format for setting the color key.
  • You are not freeing the sprite before quitting. This is poor form, but it should not actually break anything.
Back to top  
DeveloperX
202192397


Joined: 04 May 2003
Posts: 1626
Location: Decatur, IL, USA
PostPosted: Sat Apr 21, 2007 2:48 am    Post subject: [quote]
{edited}


I know why its closing.

TWO reasons jump at me, now that I've spent more than 5 seconds looking at the code.

reason 1. you are assuming that anything other than SDL_KEYDOWN, SDL_KEYUP, or SDL_QUIT are not supposed to happen.
you return 3 as a default in DetermineEventType()
you fail to realize that NO events are being reported as "3" so, you're closing the program in main() when you call SDL_Quit for case 3

reason 2. your switch / case section in main() is poorly written.
you should have a break; statement for each case.

concept
Code:

switch (value)
{
 case 0:
 {
  handlenull();
 } break;
 case 1:
 {
  handleone();
 } break;
 case 2:
 {
  handletwo();
 } break;
 default:
 {
  handledefault()
 } break;
} // end switch


hope that helped
:)
_________________
Principal Software Architect
Rambling Indie Games, LLC

See my professional portfolio
Back to top  
Captain Vimes
Grumble Teddy


Joined: 12 May 2006
Posts: 225
Location: The City Streets
PostPosted: Tue Apr 24, 2007 12:01 pm    Post subject: [quote]
Oh god... after reading your guys' posts I feel like such an idiot... durrrh. Thank you. It's working now.
_________________
"Sometimes it is better to light a flamethrower than to curse the darkness."
- Terry Pratchett
Back to top  
DeveloperX
202192397


Joined: 04 May 2003
Posts: 1626
Location: Decatur, IL, USA
PostPosted: Tue Apr 24, 2007 5:54 pm    Post subject: [quote]
Maestro134 wrote:
Oh god... after reading your guys' posts I feel like such an idiot... durrrh. Thank you. It's working now.


Don't feel like an idiot. Its easy to get lost/mixed up when you're just starting to learn something new. God knows I had a hell of a time learning Win32/DirectX stuff years ago....*shudders*

Let me know if you need anything else man. I'm always happy to help.
_________________
Principal Software Architect
Rambling Indie Games, LLC

See my professional portfolio
Back to top  
Post new topic Reply to topic Page 1 of 1 All times are GMT
 

RPGDX >> Forums >> Design and programming >> DevX, Are you there?


Display posts from previous:   
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
Template © 2003 by Bjørn Lindeijer
Powered by phpBB © 2001, 2005 phpBB Group