Hi everybody!

I have implement an MDI application under MFC.

Briefly I have to make my application to do what you can see at:


There you can find a screen shot of my application. How you can observe
there are two child windows (in this example, but in general there could be
more) displaying each one a bitmap. For each child window the user can set a
transparency value (an alpha value) so that putting that window on another
he can compare the two images (medical interest). Obviously what you see in
the screen shot is a fake example (otherwise I would not be here): in this
example the "sunset" bitmap has a 70% of opacity and the "bmw" bitmap has
100% o opacity; as you can see the "sunset" window is focused and lays above
the "bmw" window. I made this fake example first sizing and positioning the
two windows, then I minimized them and I restore the "bmw" window first and
then the "sunset" window. But, if I move the windows they not repaint
themselves properly. In fact I had subclassed the OnEraseBkgnd and the
OnPaint of my child windows and then I had used the AlphaBlend method to
paint the bitmap (I'll have to subclass also the OnMove when a child window
hasn't 100% opacity value). The problem is that on moving, sizing and so on,
before repainting with the AlphaBlend method I need to repaint what lays
under the focused child windows that is moving, sizing and so on. This means
that I had to repaint the parent window (the MDI container) and eventually
the sibling windows (the other MDI children) in the moving child client

But I don't know how to do this!

Is there anybody that's able to help me?

ThankYou in advance for all Your answers!

Gianpiero Riva