3 Comments

1. 

   Mehmet on May 12, 2012 at 11:19 am

   What i have to do if i want to translate parallax background on x-axis?

   Reply
2. 

   Scott on June 30, 2014 at 11:17 am

   I’m getting back exception errors with the first background in this video, what’s wrong with my code?

   //Allegro5 libraries.
   #include
   #include
   #include
   #include
   #include
   #include
   #include

   const int SCREEN_WIDTH = 800;
   const int SCREEN_HEIGHT = 600;
   const int FPS = 60;

   enum KEYS {UP, DOWN, LEFT, RIGHT, SPACE}; //The keys for our player’s movement.
   bool keys[5] = {false, false, false, false, false};

   struct Background
   {
   float x;
   float y;
   float velX;
   float velY;
   int dirX;
   int dirY;

   int width;
   int height;

   ALLEGRO_BITMAP *image;
   };

   void InitBackground(Background &back, float x, float y, float velx, float vely, int width, int height, int dirX, int dirY, ALLEGRO_BITMAP *image);
   void UpdateBackground(Background &back);
   void DrawBackground(Background &back);

   int main(void)
   {
   int x = SCREEN_WIDTH / 2;
   int y = SCREEN_HEIGHT / 2;

   Background back;

   bool done = false; //Declaring our gameOver variable for when the game ends.

   bool redraw = false; //Declaring our redraw variable to smooth out movement.

   //Allegro Variables.
   ALLEGRO_DISPLAY *gameDisplay = NULL; //Initializing a display variable from the ALLEGRO_DISPLAY class.
   ALLEGRO_EVENT_QUEUE *eventQueue = NULL;
   ALLEGRO_TIMER *gameTimer = NULL;
   ALLEGRO_BITMAP *backImage = NULL; //Initializing our background image.
   ALLEGRO_FONT *font18 = NULL;

   if(!al_init()) //Conditional checks to see if Allegro is initialized.
   {
   al_show_native_message_box(NULL, NULL, NULL,
   “failed to initialize Allegro.”, NULL, NULL);

   return -1;
   }

   gameDisplay = al_create_display(SCREEN_WIDTH, SCREEN_HEIGHT); //Sets the display variable to create a 800 x 400 display window.

   if(!gameDisplay) //Conditional checks to see if the display was properly initialized.
   {
   al_show_native_message_box(NULL, NULL, NULL,
   “failed to initialize display.”, NULL, NULL);

   return -1;
   }

   al_init_primitives_addon(); //Initializing the Allegro Primitives addon.
   al_install_keyboard(); //Installing keyboard functionality for player input.
   al_init_font_addon();
   al_init_ttf_addon();

   backImage = al_load_bitmap(“starBG.png”);
   InitBackground(back, 0, 0, 1, 0, SCREEN_WIDTH, SCREEN_HEIGHT, -1, 1, backImage);

   font18 = al_load_font(“arial.ttf”, 18, 0);

   eventQueue = al_create_event_queue(); //Creating our event queue object.
   gameTimer = al_create_timer(1.0 / FPS); //Creating our timer object.

   //Event sources.
   al_register_event_source(eventQueue, al_get_keyboard_event_source()); //Keyboard event source.
   al_register_event_source(eventQueue, al_get_display_event_source(gameDisplay)); //Display event source.
   al_register_event_source(eventQueue, al_get_timer_event_source(gameTimer)); //Timer event source.

   al_start_timer(gameTimer);

   while(!done)
   {
   ALLEGRO_EVENT myEvent;
   al_wait_for_event(eventQueue, &myEvent);

   if(myEvent.type == ALLEGRO_EVENT_KEY_DOWN) //Condition to check for a key press by the player.
   {
   //Checking for which key by keycode.
   switch(myEvent.keyboard.keycode)
   {
   //Keyboard arrows for player movement.
   case ALLEGRO_KEY_UP:
   keys[UP] = true; //Player moves up.
   break;
   case ALLEGRO_KEY_DOWN:
   keys[DOWN] = true; //Player moves down.
   break;
   case ALLEGRO_KEY_LEFT:
   keys[LEFT] = true; //Player moves left.
   break;
   case ALLEGRO_KEY_RIGHT:
   keys[RIGHT] = true; //Player moves right.
   break;

   case ALLEGRO_KEY_SPACE: //Player shoots the ship’s guns.
   keys[SPACE] = true;
   break;

   case ALLEGRO_KEY_ESCAPE: //if ESC is pressed, game is over.
   done = true;
   break;
   }
   }
   else if(myEvent.type == ALLEGRO_EVENT_KEY_UP) //Condition to check for keys being released on the keyboard.
   {
   //Checking for which key by keycode.
   switch(myEvent.keyboard.keycode)
   {
   //Releasing the keys.
   case ALLEGRO_KEY_UP:
   keys[UP] = false; //The Up key is released.
   break;
   case ALLEGRO_KEY_DOWN:
   keys[DOWN] = false; //The Down key is released.
   break;
   case ALLEGRO_KEY_LEFT:
   keys[LEFT] = false; //The Left key is released.
   break;
   case ALLEGRO_KEY_RIGHT:
   keys[RIGHT] = false; //The Right key is released.
   break;

   case ALLEGRO_KEY_SPACE: //Player stops shooting the ship’s guns.
   keys[SPACE] = false;
   break;
   }
   }
   else if(myEvent.type == ALLEGRO_EVENT_DISPLAY_CLOSE)
   {
   done = true;
   }
   else if(myEvent.type == ALLEGRO_EVENT_TIMER) //Our update function.
   {
   UpdateBackground(back);
   redraw = true;
   }

   if(redraw && al_is_event_queue_empty(eventQueue))
   {
   DrawBackground(back);
   redraw = false;

   al_flip_display(); //Flip the display once every 1/30 of a second with the back buffer display.
   al_clear_to_color(al_map_rgb(0, 0, 0)); //clear the display to black every 1/30 of a second.
   }
   }

   al_rest(3.0); //Pausing the program for 3 seconds after everything’s run.

   //Destroying objects for clean up.
   al_destroy_bitmap(backImage);
   al_destroy_timer(gameTimer);
   al_destroy_event_queue(eventQueue);
   al_destroy_font(font18);
   al_destroy_display(gameDisplay);

   return 0;
   }

   void InitBackground(Background &back, float x, float y, float velx, float vely, int width, int height, int dirX, int dirY, ALLEGRO_BITMAP *image)
   {
   back.x = x;
   back.y = y;
   back.velX = velx;
   back.velY = vely;
   back.width = width;
   back.height = height;
   back.dirX = dirX;
   back.dirY = dirY;
   back.image = image;
   }
   void UpdateBackground(Background &back)
   {
   back.x += back.velX * back.dirX;
   if(back.x + back.width <= 0)
   back.x = 0;
   }
   void DrawBackground(Background &back)
   {
   al_draw_bitmap(back.image, back.x, back.y, 0);

   if(back.x + back.width < SCREEN_WIDTH)
   al_draw_bitmap(back.image, back.x + back.width, back.y, 0);
   }

   Reply
3. 

   sand3r on July 14, 2014 at 6:48 am

   Mike, You’ve forgotten about

   al_destroy_timer(timer);

   😉

   Reply