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CWnd Flicker when resizing a window

Posted on 2003-11-14
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Last Modified: 2013-11-20
I have a class derived off of CWnd (CDataTable).

I have the application setup in such a way that when you resize the main window, the CDataTable object will also scale to fit a specified ratio of the screen.

The problem is, when I resize the window, and the CDataTable resizes, the data table produces a flicker effect.

I have tried adding a double-buffer to the CDataTable's WM_PAINT message before painting, but it doesn't affect anything.

I am hoping to figure out either how to stop the flicker, or an easy way to display a flicker free bounding region in place of the entire table when resizing.  Essentially, I need absolutely NO FLICKER;
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Question by:r2far
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LVL 19

Expert Comment

by:Dexstar
ID: 9751872
r2far:

> I am hoping to figure out either how to stop the flicker, or an easy way to
> display a flicker free bounding region in place of the entire table when
> resizing.  Essentially, I need absolutely NO FLICKER;

Have you tried overriding OnEraseBkGnd() and returning TRUE to block the default erasing process?  That's helped me out a lot in the past.

Hope That Helps,
Dex*
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LVL 19

Expert Comment

by:Dexstar
ID: 9751885
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Author Comment

by:r2far
ID: 9752086
I had already overriden OnEraseBackground() and returned true from it before the base class call.

The link helps but doesn't completly solve my problem.

I can use 'LockWindowUpdate();' to prevent redraw of the object while resizing, but I was hoping to at least have a minimal bounding region to show how the CWnd object is being resized as the user resizes the entire application.

I think what I need is something to inicate when resizing hs stopped.  then I could use that and the OnSize() message to control when I display the full screen, or when I display the bounding region only.

I am getting closer to a solution though
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LVL 4

Author Comment

by:r2far
ID: 9752091
If I can get the application to tell me when sizing starts and when sizing ends, i can actually draw the bounding region using the view.  But I need those start and end points.
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Accepted Solution

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Zoppo earned 750 total points
ID: 9753476
Hi r2far,


try calling
      SetClassLong( m_hWnd, GCL_STYLE, GetClassLong( m_hWnd, GCL_STYLE ) & ~( CS_HREDRAW | CS_VREDRAW ));
within a function of the CWnd after window is created (i.e. in an overridden Create)

Lot of windows have by default set the class styles CS_HREDRAW | CS_VREDRAW which indicate the window is
comleteley redrawn when horizontal or vertical resized.

WM_SIZE message is generated while resizing if windows is set to draw windows while move/size ... so WM_SIZE
handler is not a start/end point of re-sizing ...

You can IMO use WM_NCLBUTTONDOWN/WM_NCLBUTTONUP to get start/end point of resize action

hope that helps,

ZOPPO
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