Hi. I'm guessing BC programmer can help me with this

I'm working on a simple game engine in C# using GDI. I've just gotten it to the point where I should be able to load an object in and have it move around the screen. I've added my animation code to a timer callback, and now it won't compile because I guess the bitmap and graphics objects are not thread safe. Could you help? I'm pretty new to multithreading. I think I need to lockbits or something, but I don't actually need to modify the bitmaps from inside the timer, just render them. Maybe you'll know a better way to structure this?

Here is the code to test the engine:
Quote

engine = new GameEngine();

Bitmap[] spr1 = new Bitmap[1];
spr1[0] = new Bitmap("Kit2.bmp");

GameEngine.Sprite1D goodly = new GameEngine.Sprite1D(spr1, 10, 10);
goodly.Animated = false;
goodly.MoveSprite(100, 100, 100);
engine.theSprites1D.Add(goodly);

class GameEngine
{
public Bitmap screenBuff = new Bitmap(320, 200);
private Graphics g;
private Timer mainTimer;

private Bitmap background = new Bitmap("thing.bmp");

public PointF pointZeroF = new PointF(0, 0);
public Point pointZero = new Point(0, 0);

public class Sprite1D
{
public string NAME = String.Empty;
public Point POSITION = new Point(0, 0);
public int Frame = 0;
public int aniTickCount = 0;
public int movTickCount = 0;
public bool Animated = true;
public bool Enabled = true;
public int MovementSpeed = 0;
public int AnimationSpeed = 0;
public Point newPosition = new Point(0, 0);
public Bitmap[] image;

public Sprite1D(Bitmap[] img, int X, int Y)
{
image = img;
Position = new Point(X, Y);
}

public void MoveSprite(int newX, int newY, int speed)
{
newPosition = new Point(newX, newY);
MovementSpeed = speed;
}

public void SetPosition(int newX, int newY)
{
Position = new Point(newX, newY);
}
}

public class Sprite4D : Sprite1D
{
public int direction = 0;
public Bitmap[] imgRight;
public Bitmap[] imgLeft;
public Bitmap[] imgUp;
public Bitmap[] imgDown;

public Sprite4D(Bitmap[] img, int X, int Y)
: base(img, X, Y)
{

}
}

public List<Sprite1D> theSprites1D = new List<Sprite1D>();
public List<Sprite4D> theSprites4D = new List<Sprite4D>();

public GameEngine()
{
g = Graphics.FromImage(screenBuff);
mainTimer = new Timer();
mainTimer.Elapsed += new ElapsedEventHandler(OnTimedEvent);
mainTimer.Interval = 10;
mainTimer.Enabled = true;
}

private static void OnTimedEvent(object source, ElapsedEventArgs e)
{
//first render background image
g.DrawImageUnscaled(background, pointZero);

//loop through all sprites
foreach (Sprite1D sprite in theSprites1D)
{
if (sprite.Enabled)
{
//animate the sprite
if (sprite.Animated)
{
if (sprite.aniTickCount == sprite.AnimationSpeed)
{
if (sprite.Frame < sprite.image.Length)
sprite.Frame++;
else
sprite.Frame = 0;

sprite.aniTickCount = 0;
}

sprite.aniTickCount++;
if (sprite.aniTickCount > 500)
sprite.aniTickCount = 0;
}

//move the sprite
if (sprite.newPosition != pointZero && sprite.MovementSpeed > 0)
{
if (sprite.movTickCount == sprite.MovementSpeed)
{
if (sprite.Position.X > sprite.newPosition.X)
sprite.Position.X--;
else
sprite.Position.X++;

if (sprite.Position.Y > sprite.newPosition.Y)
sprite.Position.Y--;
else
sprite.Position.Y++;

sprite.movTickCount = 0;
}

sprite.movTickCount++;
if (sprite.movTickCount > 500)
sprite.movTickCount = 0;
}

g.DrawImageUnscaled(sprite.image[sprite.Frame], sprite.Position);
}
}
}
}

Any public static (SHARED in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

now it won't compile because I guess the bitmap and graphics objects are not thread safe

I don't understand why it wouldn't be able to compile. Threading problems such as this usually result in an InvalidOperationException at run-time.

I see what your saying, but I don't understand why your game doesn't just run at full CPU speed if you're not using a timer to update your frames.

Could you explain to me how I should do this instead of using a timer? If you know of any examples of rendering bitmaps using GDI at a specific speed, that would be useful. I'll take a look at the code for your game when I have some time.