Image transistion

Hi,

I wanted to make a simple image effect. I want a bitmp to fade to %100 transparency for example. I'm not sure how this would be done in a general sense. I'm working on win32.

I was thinking that I could have an image class with a member that represents opactiy:

    class FadeImage {
        Bitmap m_Img;
        double m_dOpacity = 100.0;
    };

When I want the image to fade, I can just call some method to initiate it, and keep generating WM_PAINT messages until it's done:

     void FadeImage::StartFade()
     {
          while (m_dOpacity != 0) {
               m_dOpacity--;
               Invalidate();
          }
     }

That would work, but the system will just block the user from doing much until the fade is done. I'm wondering how packages like flash do it. They can carry a fade out while still allowing mouse interaction. What's the general way to do something like this?

Thanks