File : simulation_state.ads

     -- A version of the game Asteroids in Ada using OpenGL.
     -- COL Gene Ressler.
     --
     -- This specification provides for communication between the graphics
   5 -- state and the simulation state of the system.
     
     with Win32.Gl;
     use  Win32.Gl;
     
  10 package Simulation_State is
     
        -- Size of the universe where simulation takes place.  It is a
        -- closed 2d universe.  Right and left edges are connected, as are
        -- top and bottom.
  15    Universe_X_Circumference : constant GlFloat := 1000.0;
        Universe_Y_Circumference : constant GlFloat := 700.0;
     
        -- Fire the ship's main engine.
        procedure Fire_Main_Engine(Is_Firing : in Boolean);
  20 
        -- Possible commands to the thrusters.
        type Firing_State_Type is
          (Spin_Left, Cancel_Spin_Left,
           Spin_Right, Cancel_Spin_Right);
  25 
        -- Fire the ship's thrusters.
        procedure Fire_Thrusters(Firing_State : Firing_State_Type);
     
        -- Fire a bullet from the ship.
  30    procedure Fire_Bullet;
     
        -- Advance the simulation clock forward.
        procedure Advance_Clock(New_Clock : in GlFloat);
     
  35    -- Return relevant facts about the space ship.
        procedure Get_Space_Ship_Geometry(Alive : out Boolean;
                                          X, Y, Theta : out GlFloat;
                                          Main_Engine_Firing : out Boolean);
     
  40 
        -- Distance between the origin of the space ship and the gun where
        -- bullets are fired.  So the coordinates of the gun are
        --   (X + Space_Ship_Gun_X * Cos(Theta), Y + Space_Ship_Gun_X * Sin(Theta))
        Space_Ship_Gun_X : constant GlFloat := 20.0;
  45 
        -- Return relevant facts about a bullet. This is an iterator.
        -- Called with Index=0, it will advance index to the index for the
        -- first bullet and return its geometry.  Each successive call
        -- automatically advances Index.  When there are no more bullets,
  50    -- it returns Index of 0.  So typical code for getting all the
        -- bullet information is:
        --
        -- Index := 0;
        -- loop
  55    --    Get_Bullet_Geometry(X, Y, Index);
        --    exit when Index = 0;
        --    ... process the x-y data here
        -- end loop;
        procedure Get_Bullet_Geometry(X, Y : out GlFloat;
  60                                  Index : in out Natural);
     
        -- Same as above for bullets, but for rocks instead.
        procedure Get_Rock_Geometry(X, Y, Radius : out GlFloat;
                                    Index : in out Natural);
  65 
        -- Explosion particles are given merely by their x-y coordinates.
        type Particle_Geometry_Type is
           record
              X, Y : GlFloat;
  70       end record;
     
        -- List of particles represents an explosion.
        type Particle_Geometry_List_Type is Array (1..8) of Particle_Geometry_Type;
     
  75    -- Either the ship is exploding or a rock.
        type Object_Type is (Space_Ship_Object, Rock_Object);
     
        -- Particles and type wrapped together make an explosion geometry.
        type Explosion_Geometry_Type is
  80      record
             Particles : Particle_Geometry_List_Type;
             Object : Object_Type;
          end record;
     
  85    -- Gets successive explosion geometries using same iterator scheme
        -- as above for rocks and bullets.
        procedure Get_Explosion_Geometry(Explosion_Geometry : out Explosion_Geometry_Type;
                                         Index : in out natural);
     
  90    -- Get the current score.  Not exactly physics, but still part of the simulation.
        procedure Get_Score(Score, High_Score : out Natural);
     
        -- Reset the simulation state to initial conditions.
        procedure Reset;
  95 
     end Simulation_State;