DCs and disappearing pixels

This is a discussion on DCs and disappearing pixels within the Windows Programming forums, part of the Platform Specific Boards category; Well, I assume this is a pretty simple question, atleast for someone a bit more experienced than me I have ...

  1. #1
    Registered User
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    Question DCs and disappearing pixels

    Well, I assume this is a pretty simple question, atleast for someone a bit more experienced than me

    I have a simple window, that allows you to draw in it using GDI functions, like an extremely simple stripped down version of MS Paint.

    Now, i'm fairly inexperienced with GDI operations at this point, and the problem is that when I minimize the window, or cover it with another window, anything I have drawn disappears.

    Now, I actually expected that, cause I have nothing so far to redraw the pixels once they have been invalidated.

    My question is, how do I save the information so that it can be redrawn next time the window needs updating? I'm just using SetPixelV to plot the pixels when the left mouse button is down, and I assume I need to preserve my window DC info somehow, but I don't know enough about the GDI yet to accomplish that

    Sorry for the long post, hope someone can clear this up for me.

  2. #2
    erstwhile
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    If you want to store the values of mouse-clicks then perhaps an array of POINT structures might help. You can then iterate through the array to draw the POINTs when you need to.
    You may prefer to use one of the std template containers like a vector or list to store these points.

  3. #3
    Just one more wrong move. -KEN-'s Avatar
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    The best way to fix this, IMHO, is with an HDC in memory. Use CreateCompatibleDC() to create it, and draw to it as well as your regualr HDC to your window. Then on WM_PAINT just BitBlt() it to the screen.

  4. #4
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    Smile

    Thanks both of you for replying. -KEN-'s idea seems to be what I needed

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