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SDL doesn't want to work...

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Hiya I copied the tutorial at http://cone3d.gamedev.net/cgi-bin/index.pl?page=tutorials/gfxsdl/tut3 and found that for some reason when I try to run it all that happens is that the whole screen goes black (like when you press Alt + F5) and then comes out of it with the command prompt showing but no screen, also I tried to output some text to the command prompt via "std::cout" at the start of "int main()" and it wasn't displayed. Here is my code: Main.cpp
#ifdef __cplusplus
    #include <cstdlib>
#else
    #include <stdlib.h>
#endif
#include <SDL/SDL.h>
#include "Sprite.h"
#include <iostream>


SDL_Surface *screen, *back;
CSpriteBase gaurdBase;
CSprite gaurd;

SDL_Surface * ImageLoad(char *file){
  SDL_Surface *temp1, *temp2;
  temp1 = SDL_LoadBMP(file);
  temp2 = SDL_DisplayFormat(temp1);
  SDL_FreeSurface(temp1);
  return temp2;
}
int InitImages(){
  back = ImageLoad("data/bg.bmp");
  return 0;
}
void DrawIMG(SDL_Surface *img, int x, int y){
  SDL_Rect dest;
  dest.x = x;
  dest.y = y;
  SDL_BlitSurface(img, NULL, screen, &dest);
}
void DrawBG(){
  DrawIMG(back, 0, 0);
}
void DrawScene(){
  gaurd.clearBG();
  gaurd.updateBG();
  gaurd.draw();
  SDL_Flip(screen);
}

int main(int argc, char *argv[])
{
    std::cout << "Hello";
  Uint8* keys;

  if ( SDL_Init(SDL_INIT_AUDIO|SDL_INIT_VIDEO) < 0 )
  {
    printf("Unable to init SDL: %s\n", SDL_GetError());
    exit(1);
  }
  atexit(SDL_Quit);

  screen=SDL_SetVideoMode(640,480,32,
                      SDL_SWSURFACE|SDL_FULLSCREEN|SDL_HWPALETTE);
  if ( screen == NULL )
  {
    printf("Unable to set 640x480 video: %s\n", SDL_GetError());
    exit(1);
  }


  gaurdBase.init("Images/Person");

  gaurd.init(&gaurdBase,screen);
  gaurd.set(350,300);
  gaurd.Speed() = 1.5;


  SDL_ShowCursor(0);

  InitImages();
  DrawBG();
  int done=0;

  while(done == 0)
  {
    SDL_Event event;

    while ( SDL_PollEvent(&event) )
    {
      if ( event.type == SDL_QUIT )  {  done = 1;  }

      if ( event.type == SDL_KEYDOWN )
      {
        if ( event.key.keysym.sym == SDLK_ESCAPE ) { done = 1; }
        //if ( event.key.keysym.sym ==SDLK_SPACE){sun.toggleAnim();}
      }
    }
    keys = SDL_GetKeyState(NULL);
    if ( keys[SDLK_UP] ) { gaurd.Y() += -1; }
    if ( keys[SDLK_DOWN] ) { gaurd.Y() += 1; }
    if ( keys[SDLK_LEFT] ) { gaurd.X() += -1; }
    if ( keys[SDLK_RIGHT] ) { gaurd.X() +=1 ; }
    DrawScene();
  }
  return 0;
}
/*
int main ( int argc, char** argv )
{
    // initialize SDL video
    if ( SDL_Init( SDL_INIT_VIDEO ) < 0 )
    {
        printf( "Unable to init SDL: %s\n", SDL_GetError() );
        return 1;
    }

    // make sure SDL cleans up before exit
    atexit(SDL_Quit);

    // create a new window
    SDL_Surface* screen = SDL_SetVideoMode(640, 480, 16,
                                           SDL_HWSURFACE|SDL_DOUBLEBUF);
    if ( !screen )
    {
        printf("Unable to set 640x480 video: %s\n", SDL_GetError());
        return 1;
    }

    // load an image
    SDL_Surface* bmp = SDL_LoadBMP("cb.bmp");
    if (!bmp)
    {
        printf("Unable to load bitmap: %s\n", SDL_GetError());
        return 1;
    }

    // center the bitmap on screen
    SDL_Rect dstrect;
    dstrect.x = (screen->w - bmp->w) / 2;
    dstrect.y = (screen->h - bmp->h) / 2;

    // program main loop
    bool done = false;
    while (!done)
    {
        // message processing loop
        SDL_Event event;
        while (SDL_PollEvent(&event))
        {
            // check for messages
            switch (event.type)
            {
                // exit if the window is closed
            case SDL_QUIT:
                done = true;
                break;

                // check for keypresses
            case SDL_KEYDOWN:
                {
                    // exit if ESCAPE is pressed
                    if (event.key.keysym.sym == SDLK_ESCAPE)
                        done = true;
                    break;
                }
            } // end switch
        } // end of message processing

        // DRAWING STARTS HERE

        // clear screen
        SDL_FillRect(screen, 0, SDL_MapRGB(screen->format, 0, 0, 0));

        // draw bitmap
        SDL_BlitSurface(bmp, 0, screen, &dstrect);

        // DRAWING ENDS HERE

        // finally, update the screen :)
        SDL_Flip(screen);
    } // end main loop

    // free loaded bitmap
    SDL_FreeSurface(bmp);

    // all is well ;)
    printf("Exited cleanly\n");
    return 0;
}*/



Sprite.h
#ifndef SPRITE_H
#define SPRITE_H

struct CSpriteFrame
{
  SDL_Surface *image;
  int pause;
};

class CSpriteBase
{
  public:
  int init(char *dir);
  ~CSpriteBase();

  CSpriteFrame *mAnim;
  int mBuilt, mNumframes, mW, mH;
};

class CSprite
{
public:
  int init(CSpriteBase *base, SDL_Surface *screen);
  void draw();
  void clearBG();
  void updateBG();
  int &Frame() { return mFrame; }
  float &Speed() { return mSpeed; }
  void toggleAnim() { mAnimating = !mAnimating; }
  void startAnim() { mAnimating = 1; }
  void stopAnim() { mAnimating = 0; }
  void rewind() { mFrame = 0; }
  int &X() { return mX; }
  int &Y() { return mY; }
  void set(int xx, int yy) { mX=xx; mY=yy; }
private:
  int mFrame;
  int mX, mY, mOldX, mOldY;
  int mAnimating;
  int mDrawn;
  float mSpeed;
  long mLastupdate;
  CSpriteBase *mSpriteBase;
  SDL_Surface *mBackreplacement;
  SDL_Surface *mScreen;
};



#endif



Sprite.cpp
#ifdef __cplusplus
    #include <cstdlib>
#else
    #include <stdlib.h>
#endif
#include <SDL/SDL.h>
#include <String>
#include "Sprite.h"

int CSpriteBase::init(char *dir)
{
  char buffer[255];
  char filename[255];
  char name[255];
  int pause=0, r=0, g=0, b=0;
  FILE *fp;
  sprintf(filename, "%s/info", dir);

  if((fp=fopen(filename, "r")) == NULL)
  {
    printf("ERROR opening file %s\n\n", filename);
    return -1;
  }
  fgets(buffer, 255, fp);
  sscanf(buffer, "FILES: %d", &mNumframes);
  mAnim = new CSpriteFrame[mNumframes];
  mBuilt = 1;
  int count = 0;
  while(!feof(fp) && count<mNumframes)
  {
    fgets(buffer, 255, fp);
    if(buffer[0] != '#' && buffer[0] != '\r' && buffer[0] != '\0'
                     && buffer[0] != '\n' && strlen(buffer) != 0)
    {
        sscanf(buffer, "%s %d %d %d %d", name, &pause, &r, &g, &b);
        sprintf(filename, "%s/%s", dir, name);
        SDL_Surface *temp;
        if((temp = SDL_LoadBMP(filename)) == NULL) return -1;
        if(r >= 0) SDL_SetColorKey(temp, SDL_SRCCOLORKEY,
                    SDL_MapRGB(temp->format, r, g, b));
        mAnim[count].image = SDL_DisplayFormat(temp);
        SDL_FreeSurface(temp);
        mAnim[count].pause = pause;
      if(!mW) mW = mAnim[count].image->w;
      if(!mH) mH = mAnim[count].image->h;

      count++;
    }
  }
  fclose(fp);
  return 0;
}

CSpriteBase::~CSpriteBase()
{
    delete []mAnim;
}

int CSprite::init(CSpriteBase *base, SDL_Surface *screen)
{
  mSpriteBase = base;
  if(mSpriteBase->mBuilt)
  {
    if(mSpriteBase->mNumframes>1) mAnimating=1;
    mBackreplacement =
               SDL_DisplayFormat(mSpriteBase->mAnim[0].image);
  }
  mScreen = screen;
}

void CSprite::clearBG()
{
  if(mDrawn==1)
  {
    SDL_Rect dest;
    dest.x = mOldX;
    dest.y = mOldY;
    dest.w = mSpriteBase->mW;
    dest.h = mSpriteBase->mH;
    SDL_BlitSurface(mBackreplacement, NULL, mScreen, &dest);
  }
}

void CSprite::updateBG()
{
  SDL_Rect srcrect;
  srcrect.w = mSpriteBase->mW;
  srcrect.h = mSpriteBase->mH;
  srcrect.x = mX;
  srcrect.y = mY;
  mOldX=mX;mOldY=mY;
  SDL_BlitSurface(mScreen, &srcrect, mBackreplacement, NULL);
}

void CSprite::draw()
{
  if(mAnimating == 1)
  {
    if(mLastupdate+mSpriteBase->mAnim[mFrame].pause*mSpeed<
                                                SDL_GetTicks())
    {
      mFrame++;
      if(mFrame>mSpriteBase->mNumframes-1) mFrame=0;
      mLastupdate = SDL_GetTicks();
    }
  }
  if(mDrawn==0) mDrawn=1;

  SDL_Rect dest;
  dest.x = mX; dest.y = mY;
  SDL_BlitSurface(mSpriteBase->mAnim[mFrame].image, NULL, mScreen,
                                                           &dest);
}



Any help would be much appreciated. On a different note I found a useful trick on www.functionx.com - returning a reference, therefore you don't need get and set functions but still can (if required) to make sure the variable isn't set outside a range. I use this for my Sprite class for Speed, Frame, X, Y, are there any disadvantages to this approach? [Edited by - Peter Conn on September 15, 2006 3:06:35 PM]

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Try this code to see if it works; it's about the most basic SDL application you can make that uses the video subsystem.


#include <SDL/sdl.h>

bool quit = false;

int main(int argc, char * argv[])
{
if (SDL_Init(SDL_INIT_VIDEO) == -1) //Init video subsystem
{
//An error occurred. Log it and abort.
fprintf(stderr, "Error initializing SDL video subsystem: %s", SDL_GetError());
return 1;
}
if (SDL_SetVideoMode(640, 480, 32, SDL_DOUBLEBUF) == NULL)
{
//Error. Log and abort
fprintf(stderr, "Error setting up video buffer: %s", SDL_GetError());
return 1;
}
while (!quit) //Loop until keypress
{
SDL_Event event;
while (SDL_PollEvent(&event))
{
if (event.type == SDL_KEYDOWN || event.type == SDL_QUIT) quit = true;
}
}
return 0;
}



Let us know what this program does. If it crashes or quits without showing a window, post any contents in the stderr.txt file.

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Well I'm using CodeBlocks and have run the program that you get when you make a new SDL application with CodeBlocks.
I've also made a program which moves a picture around the background so I think its something to do with the sprites.

The stderr.txt contains this one line:
Fatal signal: Segmentation Fault (SDL Parachute Deployed)

Does that help?

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Oh hell! I just realised - I had misspelt the background file name!
I'm sorry for that, is there thing in the furture I can do so that next time an image file goes missing the image just isn't displayed, without taking down the whole application.?

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Maybe make a replacer image that would be displayed in it's place if it's not find. Sort of how a web-browser works by displaying a red X in place of the image that doesn't work (just do a lot of error checking to display the red x, if the image can't be found.

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