I am writing some code to acquire data through a port and plot it on screen in real time, more or less.  I am trying to keep the amount of code to a minimum for performance.  In my OnDraw function I separate the axes, gridlines, and labels from the code that plots the data so that the more permanent features are not regenerated every time.  I use a boolean flag to indicate when these features are to be redrawn.  
      A problem arises when I move a window over another view.  The background is redrawn when I reveal the window again, but none of my graphics, because the flag has not been set high to indicate that they should be redrawn.  So I am trying to set the flag in the handlers for the various windows events such as OnSize, OnMove, and OnShowwindow.  The only one of these that works is the OnSize handler.  So my graphics are regenerated when I resize a window, but not when I move it or when i minimize then restore it. Are there no WM_MOVE messages sent when I move a window?  

More importantly, is my method appropriate, or should I be calculating a rectangle to invalidate for every data point that comes in.  Or should I do both things?

I am giving away most of my points for some seemingly easy questions because I  expect I will be following up a bit.  I want an understanding of what is happening, for instance, when I slide a dialog box across my view and everything under the box is erased.
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plarocheConnect With a Mentor Commented:
The thing that is happening is that your unflagged regions are marked as invalidated by the system when another window is moved over.
Not only should you check for your boolean flag but you should also check if your axis region, for example, is included in the invalidated region.
To get the invalidated region you can use CDC::GetClipBox, then you will need to check if your rect is in that region. For that you can use CRect::IntersectRect.

akuruAuthor Commented:
Edited text of question
akuruAuthor Commented:
I figured that the system was invalidating the part of the view that is hidden.  The question then becomes: by what mechanism does the system alert the view that it now has an invalid region caused by the view being obscured by something else?  If part of my view is hidden, portions of the axes and or gridlines will almost certainly be in the invalid rectangle.  The only time an invalid region will not include the more permanent features is when the invalidation occurs from a new data point.

In my OnSize, I set the m_bRedraw flag high, and my OnDraw function redraws everything, scaling it appropriately.  Where can I set that flag high when part of my view is invalidated by another window overlapping it?  Or when a window is restored from being minimised?  
You view will get a OnDraw when the system has invalidated it, it comes by naturally. This is the place where the region check should take place, and then maybe set your flags high.

The check for the invalidated region will treat all cases of maximization, etc... because it's where every drawing occurs.
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