Question

Imagine you want to animate some object on a WinForm. You setup a timer to update the state or model, and override the paint event of the Form. But from there, what’s the best way to continually repaint the Form for the animation?

• Invalidate the Form as soon as you are done drawing?
• Setup a second timer and invalidate the form on a regular interval?
• Perhaps there is a common pattern for this thing?
• Are there any useful .NET classes to help out?

Each time I need to do this I discover a new method with a new drawback. What are the experiences and recommendations from the SO community?

Answer 1

In some situations, it’s faster and more convenient to not draw using the paint event, but getting the Graphics object from the control/form and painting ‘on’ that. This may give some troubles with opacity/anti aliasing/text etc, but could be worth the trouble in terms of not having to repaint the whole shabang. Something along the lines of:

private void AnimationTimer_Tick(object sender, EventArgs args) {     // First paint background, like Clear(Control.Background), or by     // painting an image you have previously buffered that was the background.     animationControl.CreateGraphics().DrawImage(0, 0, animationImages[animationTick++]));  } 

I use this in some Controls myself, and have buffered images to ‘clear’ the background with, when the object of interest moves or need to be removed.