DOCUMENT:Q74474  10-JUN-1999  [win16sdk]
TITLE   :INFO: Killing the Parent of a Modal Dialog Box
PRODUCT :Microsoft Windows Software Development Kit
PROD/VER:WINDOWS:3.1
OPER/SYS:
KEYWORDS:kb16bitonly kbDlg kbSDKPlatform

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3.00 3.10
WINDOWS
kbprg

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The information in this article applies to:

 - Microsoft Windows Software Development Kit (SDK) 3.1 
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SUMMARY
=======

An application cannot destroy the parent of a modal dialog box. When the modal
dialog box ends, control is returned to its parent. If the parent is destroyed,
control is given to a nonexistent window and the application crashes.

When a parent window receives the destroy message, it is too late to destroy a
child modal dialog box. The destroyed dialog box does not return control until
after all the existing messages are processed, including the final destruction
of the parent window.

Therefore, it is imperative that all generational parents of a modal dialog box
be disabled and have no way of receiving a WM_DESTROY message while the modal
dialog box is active.

MORE INFORMATION
================

This situation does not affect modeless dialog boxes. Therefore, if the design
of a system cannot rule out the preceding problem, use a modeless dialog box
instead of a modal dialog box.

Because the Task Manager can kill any program at any time, there is no absolute
protection from the parent being closed. The optimal solution is to forgo modal
dialog boxes in favor of modeless dialog boxes. When a modeless dialog box is
created, it may disable its parental windows.

Additional query words: 3.00 3.10 wm_close

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Keywords          : kb16bitonly kbDlg kbSDKPlatform 
Technology        : kbAudDeveloper kbWin3xSearch kbSDKSearch kbWinSDKSearch kbWinSDK310
Version           : WINDOWS:3.1
Issue type        : kbinfo

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