Repaint a window

This is a discussion on Repaint a window within the Windows Programming forums, part of the Platform Specific Boards category; How can I repaint a window? I've tried update window but it never works for some reason....

  1. #1
    Semi n00b Mithoric's Avatar
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    Repaint a window

    How can I repaint a window? I've tried update window but it never works for some reason.

  2. #2
    pronounced 'fib' FillYourBrain's Avatar
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    UpdateWindow just forces a WM_PAINT message. You have to answer that WM_PAINT message by redrawing anything you drew before. Using the HDC given from BeginPaint() you need to redraw.
    "You are stupid! You are stupid! Oh, and don't forget, you are STUPID!" - Dexter

  3. #3
    Registered User glUser3f's Avatar
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    you can also use Invalidate

  4. #4
    Semi n00b Mithoric's Avatar
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    I gathered I was handling the WM_PAINT message...
    Code:
    case WM_PAINT:
      {
        EnumChildWindows(hwnd,EnumProc,0);
        PAINTSTRUCT ps;
        HDC dc = BeginPaint(hwnd,&ps);
        DrawMCB(hwnd,dc,status);
        EndPaint(hwnd,&ps);
        ReleaseDC(hwnd,dc);
        return 0;
      }

  5. #5
    pronounced 'fib' FillYourBrain's Avatar
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    easiest way is to use your debugger. break inside the WM_PAINT handler. See what happens. If it doesn't get there, you aren't InvalidateRect()-ing in the right place.
    "You are stupid! You are stupid! Oh, and don't forget, you are STUPID!" - Dexter

  6. #6
    Semi n00b Mithoric's Avatar
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    Ok, well I have to learn to use the debugger first so I'll go off to read the relevant stuff on that and then try.

    Thanks so far.

  7. #7
    train spotter
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    You must use InvalidateRect() then UpdateWindow()

    that is tell the app
    InvalidateRect();//this is the area I want updated
    UpdateWindow()//do it NOW by bypassing the msg que

    If the rect invalidated is empty the paint msg will not be sent/responded to.

    if using MSVC, highlight a line in your code. Press F9 to place a break point (a red dot appears). Run the app and it will stop at the break point. Drag a variable to teh 'watch' window or highlight to see the contents.

    PS Normally you have to ReleaseDC() but seeing you use the one BeginPaint() created (and will be cleaned up by EndPaint() ) you don't need the ReleaseDC(). (as you did not GetDC() it)
    Last edited by novacain; 12-19-2003 at 01:15 AM.
    "Man alone suffers so excruciatingly in the world that he was compelled to invent laughter."
    Friedrich Nietzsche

    "I spent a lot of my money on booze, birds and fast cars......the rest I squandered."
    George Best

    "If you are going through hell....keep going."
    Winston Churchill

  8. #8
    Semi n00b Mithoric's Avatar
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    I've tried and tried but still can't get it to update!

    Code:
            rc.left = p1.x;
            rc.top = p1.y;
            rc.right-=rc.left;
            rc.bottom-=rc.top;
            InvalidateRect(hwnd,&rc,TRUE);
            UpdateWindow(hwnd);
    I gathered that was right. Or should I be using the windows parent there?

  9. #9
    train spotter
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    The parent hwnd, as it is the dialogs callback that will get the msg to paint.
    "Man alone suffers so excruciatingly in the world that he was compelled to invent laughter."
    Friedrich Nietzsche

    "I spent a lot of my money on booze, birds and fast cars......the rest I squandered."
    George Best

    "If you are going through hell....keep going."
    Winston Churchill

  10. #10
    Semi n00b Mithoric's Avatar
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    Yeah I figured that out when I read the MSDN stuff again . ...

    Cheers anyways!

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