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SetWindowRgn

Posted on 2001-09-12
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Last Modified: 2013-12-03
Hi, experts.
   I have a problrm with setWindowRgn. I continuously resize my window and every time I set a new region for my window. Everything works fine, but after some time I start experiencing something like "internal windows resource leaks" - when I drag the window it is being dragged slower and slower, and not only that it affects all other non-rectangular windows, like I tried to run Winamp or Odigo they were also slow, but as soon as I closed my application, Winamp and Odigo... started moving fastly without any delay while gragging, seems like when I close my appl. resources are cleaned up, but how can I do it at arun time?
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Question by:alex108
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14 Comments
 
LVL 20

Expert Comment

by:Madshi
ID: 6478814
After you've set the new region, you have to delete the old one with "DeleteObject".

Something like this:

[creating]
wnd = CreateWindow(...);
rgn = CreateRectRgn(...);
SetWindowRgn(wnd, rgn, ...);

[changing region]
oldRgn = rgn;
rgn = CreateRectRgn(...);
SetWindowRgn(wnd, rgn, ...);
DeleteObject(oldRgn);

Regards, Madshi.
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LVL 20

Expert Comment

by:Madshi
ID: 6478818
P.S: "rgn" should be a global variable in this case, or a class variable, while "oldRgn" could be a local one.
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Author Comment

by:alex108
ID: 6479461
I tried that and so many other things - it doesn,t solve the problem.
Take in your own CWnd(CDialog) derived class in OnSize
do something like:

void CMyWnd::OnSize(UINT nType, int cx, int cy)
{
     CCustomizedDlg::OnSize(nType, cx, cy);
     HRGN oldRgn = m_hRgn;
     m_hRgn = CreateEllipticRgn(0,0,cx, cy+40);
     //SetWindowRgn(NULL,FALSE);
     SetWindowRgn(hRgn,TRUE);
     DeleteObject(oldRgn);
}

and then try to drag the window after resizing for a while
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LVL 20

Expert Comment

by:Madshi
ID: 6480348
Just one more try, before I invest the time to test it myself: Could you please call SetWindowRgn with "FALSE". Just to make sure, that that won't fix the problem... If it does not, I will try this whole thing myself.

Regards, Madshi.
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Author Comment

by:alex108
ID: 6481798
Unfortunately it doesn't.
Regards, Alex
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LVL 15

Expert Comment

by:NickRepin
ID: 6483920
SDK says: "After a successful call to SetWindowRgn, the system owns the region specified by the region handle hRgn. The system does not make a copy of the region. Thus, you should not make any further function calls with this region handle. In particular, do not close this region handle".

Try just this:

void CMyWnd::OnSize(UINT nType, int cx, int cy)
{
    CCustomizedDlg::OnSize(nType, cx, cy);
    SetWindowRgn(CreateEllipticRgn(0,0,cx, cy+40),TRUE);
}
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LVL 20

Expert Comment

by:Madshi
ID: 6484449
Yes, according to the documentation Nick seems to be right. However, the only full example I found on www.Microsoft.com DOES delete the old region:

http://msdn.microsoft.com/code/default.asp?url=/msdn-files/026/001/876/NonRect/Source%20Files/MainFrm_cpp.asp

Strange thing.

Regards, Madshi.
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LVL 15

Expert Comment

by:NickRepin
ID: 6485121
>>DOES delete the old region:

I did not in my program, and all worked fine.
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LVL 20

Expert Comment

by:Madshi
ID: 6485527
>> I did not in my program, and all worked fine.

Yeah, but that's no proof. As it is with memory/resource leaks: All seems to work fine until you've consumed all available resources (at least in win9x).

But as I said in my previous comment: I guess that you're right and that Windows actually does delete the old region itself. I just found it a bit strange, that the only full example contradicts the documentation...
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Author Comment

by:alex108
ID: 6486238
Sorry, but it's not gonna solve the problem, whether you delete old region or not. Interesting enough, if you set rectangular regions you don't feel resoource leaks, only non-rectangular is a problem.
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LVL 14

Expert Comment

by:AlexVirochovsky
ID: 6492989
>>you don't feel resoource leaks
May be problem in other place of your apps.
For detect memory leaks I use TaskInfo2000 from
www.iarsn.com  Try it!
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