How do I set an umanaged dialog as the Owner of a WinForm Form?

Question

I need to be able to set a WinForm dialog's Owner's HWND. In unmanaged I have a background thread that gets the HWND for the window in front. The code then calls ::GetParent(frontHWND) to see if it needs to hide a different non-modal MFC dialog. When the WinForm dialog is the frontHWND, I always get NULL back for the GetParent call. I have also tried GetOwner realizing .Net tried to cleanup the difference between Parent and Owner. Looking at the WinForm dialog w/ Spy++, it also say the WinForm has no parent or owner. I have passed in NativeWindow ^natWin = gcnew NativeWindow(); natWin->AssignHandle(IntPtr(hwndParent)); managedDlg->ShowDialog(natWin); The above code didn't set the owner of the WinForm. I tried calling the Win32 SetParent from the WinForm code in OnFormShown(), but the locked up the MFC application and the WinForm. Can someone explain how to get my unmanaged dialog/app to be the owner/parent of the managed winform?

Answer 1

The Form will have a Handle property which will give you the HWND of the form window.

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Answer 2

I can get the Form's handle. I can't get the form's owner's/parent's handle, b/c when calling the Win32 call GetParent(formHwnd), it returns NULL. Also, Spy++ says the Form's Parent/Owner is NULL.

Answer 3

I can get the Form's handle. I can't get the form's owner's/parent's handle, b/c when calling the Win32 call GetParent(formHwnd), it returns NULL. Also, Spy++ says the Form's Parent/Owner is NULL.

Yeah, so what's wrong with that? That probably means the form is a top level window.

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http://blog.voidnish.com

Answer 4

I open the Form by calling NativeWindow ^natWin = gcnew NativeWindow(); natWin->AssignHandle(IntPtr(hwndParent)); managedDlg->ShowDialog(natWin); Therefore, I'm expecting the call to ::GetParent(formHwnd) to return me the HWND that I passed in when I opened the Form with ShowDialog(natWin) earlier. BTW, thanks for the help.

Answer 5

Apparently, that alone does not do what you think it will. You may also need to explicitly set the Parent property.

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http://blog.voidnish.com

Answer 6

Hi byronasdf,

I think the GetWindow Function is what you want.

GetWindow Function

Retrieves a handle to a window that has the specified relationship (Z-Order or owner) to the specified window.

The following is my test code, so you can reference it:

 

 [DllImport("user32.dll", SetLastError = true)]
 static extern IntPtr GetWindow(IntPtr hWnd, GetWindow_Cmd uCmd);

 enum GetWindow_Cmd : uint
 {
  GW_HWNDFIRST = 0,
  GW_HWNDLAST = 1,
  GW_HWNDNEXT = 2,
  GW_HWNDPREV = 3,
  GW_OWNER = 4,
  GW_CHILD = 5,
  GW_ENABLEDPOPUP = 6
 }

 private void button2_Click(object sender, EventArgs e)
 {
  this.label3.Text = GetWindow(this.Handle, GetWindow_Cmd.GW_OWNER).ToString("x");
 }

Since I'm not familiar with C++ syntax, so I use the C# code test this function, you just need to use the same function in your C++ project.

And in the native code, you just need to use the SetParent function to set the managed Form as a child to the native window.

If there's any concern, please feel free to let me know.

Have a nice day!

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Mike [MSFT]
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Answer 7

Hi byronasdf,

I am writing to check the status of the issue on your side. 

What about this problem now? 

Would you mind letting us know the result of the suggestions?

Best wishes,

---

Mike [MSFT]
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Answer 8

Sorry for the delay. Calling GetWindow(managedHwnd, GW_OWNER) returns the HWND that I wrap then pass into managedDlg->ShowDialog(WrappedNatWindow). It will also return the HWND of my app if I don't pass anything into ShowDialog(). I haven't had time to go back and test the GetParent(), GetOwner() and understand better why the GetOwner didn't return the HWND I was expecting. I also want to test calling the Win32 SetParent(mngdHwnd, UnmngdHwnd) and see why it was causing my dialog and app to lock up. I'll try to repost back here if I ever make time to retest. Thanks for the help.

Answer 9

Hi byronasdf,

Owner is the *Window responsible for a control or dialog (for example, responsible for creating/destroying the window).

Parent is the next-senior window* to a control or dialog in the window chain, but isn't actually responsible for it (doesn't necessarily care about its lifecycle, etc). A window's parent can also be its owner.

*Window vs window: Window is an actual window displayed on the screen; window is any object with a HWND (includes buttons, panels, etc).

 

GetOwner gets the owner of a non-child window

GetParent gets the parent of a child window window

 

Best wishes,

---

Mike [MSFT]
MSDN Community Support | Feedback to us
Get or Request Code Sample from Microsoft
Please remember to mark the replies as answers if they help and unmark them if they provide no help.