SDL Not redrawing screen after Flip or Update - sdl

Question

I recently started programming with SDL and I've been following some tutorials on gamedevgeek and lazyfoo. I got to show images on the screen, but when I tried to move them I realized the screen was not updating correctly, making the sprite leave a trace, like in this image:
As you can see, the sprite started out in the top left corner, and it left a trace throughout its path to the bottom right.
Some info that can help:
I'm using a raspberry pi with raspbian.
I'm using SDL 1.2.
What have I tried:
I tried changing the last parameter of SDL_SetVideoMode to SDL_HWSURFACE, SDL_SWSURFACE, SDL_DOUBLEBUF, SDL_FULLSCREEN
I tried to switch between SDL_Flip(screen) and SDL_UpdateRect(screen, 0, 0, 0, 0); when I changed the parameter of SDL_SetVideoMode.
Here is my code.
#include "SDL.h"
#define SCREEN_WIDTH 640
#define SCREEN_HEIGHT 480
int main ( int argc, char *argv[] )
{
SDL_Surface *screen, *temp, *sprite;
SDL_Rect rcSprite;
SDL_Event event;
Uint8 *keystate;
int colorkey, gameover;
SDL_Init(SDL_INIT_VIDEO);
// screen = SDL_SetVideoMode(SCREEN_WIDTH, SCREEN_HEIGHT, SDL_DOUBLEBUF | SDL_FULLSCREEN);
// screen = SDL_SetVideoMode(SCREEN_WIDTH, SCREEN_HEIGHT, SDL_HWSURFACE);
screen = SDL_SetVideoMode(SCREEN_WIDTH, SCREEN_HEIGHT, SDL_SWSURFACE);
temp = SDL_LoadBMP("sprite.bmp");
sprite = SDL_DisplayFormat(temp);
SDL_FreeSurface(temp);
colorkey = SDL_MapRGB(screen->format, 255, 0, 255);
SDL_SetColorKey(sprite, SDL_SRCCOLORKEY | SDL_RLEACCEL, colorkey);
rcSprite.x = 0;
rcSprite.y = 0;
gameover = 0;
while (!gameover)
{
if (SDL_PollEvent(&event)) {
switch (event.type) {
case SDL_KEYDOWN:
switch (event.key.keysym.sym) {
case SDLK_ESCAPE:
gameover = 1;
break;
}
break;
}
}
keystate = SDL_GetKeyState(NULL);
if (keystate[SDLK_LEFT] )
rcSprite.x -= 2;
if (keystate[SDLK_RIGHT] )
rcSprite.x += 2;
if (keystate[SDLK_UP] )
rcSprite.y -= 2;
if (keystate[SDLK_DOWN] )
rcSprite.y += 2;
SDL_BlitSurface(sprite, NULL, screen, &rcSprite);
// SDL_Flip(screen);
SDL_UpdateRect(screen, 0, 0, 0, 0);
}
SDL_FreeSurface(sprite);
SDL_FreeSurface(grass);
SDL_Quit();
return 0;
}
What am I doing wrong? Needless to say that I'm very new to the linux world, as well as the raspberry pi's, as well as SDL's :)

Answer 1

You call to SDL_SetVideoMode() is incorrect, your code should not compile, enable your compiler warnings.
The function takes four arguments:
SDL_Surface *SDL_SetVideoMode(int width, int height, int bpp, Uint32 flags);
so it should be something like:
screen = SDL_SetVideoMode(SCREEN_WIDTH, SCREEN_HEIGHT, 32 , SDL_SWSURFACE);
if( !screen )
//print your warning and exit.
Also your screen surface is never cleared and the sprite remains. Either redraw the entire screen with sprites or clear the surface
SDL_FillRect( screen , NULL , 0x0 ) ; //fills the entire surface with 0x0 .