SDL C++ Base Code (for SDL 1.2 and below)

Contents

• Introduction
• Source Listing

Introduction

Note: This document is for SDL 1.2 and below.
For the SDL2 version, click here.

SDL example that allows user to move an object using arrow keys. This is meant to be used as a convenient single-file starting point for more complex projects.

Tested with Code::Blocks on Windows 7. You will need the SDL files. If building with GCC/MinGW, use these linker options:

      -lmingw32
      -lSDLmain
      -lSDL

Here is a screenshot of what the program looks like when it runs:

Source Listing

/*
SDL example that allows user to move an object using arrow keys.
This is meant to be used as a convenient single-file starting point for
more complex projects.

Tested with Code::Blocks on Windows 7. You will need the SDL files.
If building with GCC/MinGW, use these linker options:
-lmingw32
-lSDLmain
-lSDL

Author: Andrew Lim Chong Liang
windrealm.org
*/
#include <stdio.h>
#include "SDL.h"
enum {
    DISPLAY_WIDTH  = 480
  , DISPLAY_HEIGHT = 320
  , UPDATE_INTERVAL = 1000/60
  , HERO_SPEED = 2
};

class Sprite {
public:
  int x, y ;
  Sprite() :x(0), y(0) {}
} ;

class Game {
public:
  Game();
  ~Game();
  void start();
  void stop() ;
  void draw();
  void fillRect( SDL_Surface* surface, SDL_Rect* rc, int r, int g, int b );
  void fpsChanged( int fps );
  void onQuit();
  void onKeyDown( SDL_Event* event );
  void onKeyUp( SDL_Event* event );
  void run();
  void update();
private:
  int keys[ SDLK_LAST ] ;
  int frameSkip ;
  int running ;
  SDL_Surface* display ;
  Sprite hero ;
};

Game::Game()
:frameSkip(0), running(0), display(NULL) {
  for ( int i=0; i<SDLK_LAST; ++i ) {
    this->keys[ i ] = 0 ;
  }
}

Game::~Game() {
  this->stop();
}

void Game::start() {
  int flags = SDL_HWSURFACE|SDL_DOUBLEBUF|SDL_ANYFORMAT ;

  /* initialize SDL */
  if ( SDL_Init(SDL_INIT_VIDEO|SDL_INIT_TIMER) ) {
    return ;
  }

  /* set video surface */
  this->display = SDL_SetVideoMode( DISPLAY_WIDTH, DISPLAY_HEIGHT, 0, flags );
  if ( display == NULL ) {
    return ;
  }
  /* Set caption */
  SDL_WM_SetCaption( "SDL Base C++", NULL );

  this->running = 1 ;
  run();
}

void Game::stop() {
  if ( display != NULL ) {
    SDL_FreeSurface( display );
  }
  SDL_Quit() ;
}

void Game::draw() {
  SDL_Rect heroRect ;

  /* Clear screen */
  fillRect( display, NULL, 255, 255, 255 );

  /* Render hero */
  heroRect.x = hero.x ;
  heroRect.y = hero.y ;
  heroRect.w = 20 ;
  heroRect.h = 20 ;
  fillRect( display, &heroRect, 255, 0, 0 );

  SDL_Flip( display );
}

void Game::fillRect( SDL_Surface* surface, SDL_Rect* rc, int r, int g, int b ) {
  SDL_FillRect( surface, rc, SDL_MapRGB(surface->format, r, g, b) );
}

void Game::fpsChanged( int fps ) {
  char szFps[ 128 ] ;
  sprintf( szFps, "%s: %d FPS", "SDL Base C++ - Use Arrow Keys to Move", fps );
  SDL_WM_SetCaption( szFps, NULL );
}

void Game::onQuit() {
  running = 0 ;
}

void Game::run() {
  int past = SDL_GetTicks();
  int now = past, pastFps = past ;
  int fps = 0, framesSkipped = 0 ;
  SDL_Event event ;
  while ( running ) {
    int timeElapsed = 0 ;
    if (SDL_PollEvent(&event)) {
      switch (event.type) {
        case SDL_QUIT:    onQuit();            break;
        case SDL_KEYDOWN: onKeyDown( &event ); break ;
        case SDL_KEYUP:   onKeyUp( &event );   break ;
        case SDL_MOUSEBUTTONDOWN: {
          break ;
        }
        case SDL_MOUSEBUTTONUP: {
          break ;
        }
        case SDL_MOUSEMOTION: {
          break ;
        }
      }
    }
    /* update/draw */
    timeElapsed = (now=SDL_GetTicks()) - past ;
    if ( timeElapsed >= UPDATE_INTERVAL  ) {
      past = now ;
      update();
      if ( framesSkipped++ >= frameSkip ) {
        draw();
        ++fps ;
        framesSkipped = 0 ;
      }
    }
    /* fps */
    if ( now - pastFps >= 1000 ) {
      pastFps = now ;
      fpsChanged( fps );
      fps = 0 ;
    }
    /* sleep? */
    SDL_Delay( 1 );
  }
}

void Game::update() {
  if ( keys[SDLK_LEFT] ) {
    hero.x -= HERO_SPEED ;
  } else if ( keys[SDLK_RIGHT] ) {
    hero.x += HERO_SPEED ;
  } else if ( keys[SDLK_UP] ) {
    hero.y -= HERO_SPEED ;
  } else if ( keys[SDLK_DOWN] ) {
    hero.y += HERO_SPEED ;
  }
}

void Game::onKeyDown( SDL_Event* evt ) {
  keys[ evt->key.keysym.sym ] = 1 ;
}

void Game::onKeyUp( SDL_Event* evt ) {
  keys[ evt->key.keysym.sym ] = 0 ;
}

int main(int argc, char *argv[]) {
  Game game ;
  game.start();
  return 0 ;
}