WM_WINDOWPOSCHANGING message
Sent to a window whose size, position, or place in the Z order is about to change as a result of a call to the SetWindowPos function or another window-management function.
A window receives this message through its WindowProc function.
#define WM_WINDOWPOSCHANGING 0x0046
Parameters
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wParam
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This parameter is not used.
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lParam
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A pointer to a WINDOWPOS structure that contains information about the window's new size and position.
Return value
Type: LRESULT
If an application processes this message, it should return zero.
Remarks
For a window with the WS_OVERLAPPED or WS_THICKFRAME style, the DefWindowProc function sends the WM_GETMINMAXINFO message to the window. This is done to validate the new size and position of the window and to enforce the CS_BYTEALIGNCLIENT and CS_BYTEALIGNWINDOW client styles. By not passing the WM_WINDOWPOSCHANGING message to the DefWindowProc function, an application can override these defaults.
While this message is being processed, modifying any of the values in WINDOWPOS affects the window's new size, position, or place in the Z order. An application can prevent changes to the window by setting or clearing the appropriate bits in the flags member of WINDOWPOS.
Note
Changes to some SWP flags, including SWP_NOACTIVATE and SWP_NOOWNERZORDER, are ignored when they are modified during WM_WINDOWPOSCHANGING.
Requirements
| Requirement | Value |
|---|---|
| Minimum supported client |
Windows 2000 Professional [desktop apps only] |
| Minimum supported server |
Windows 2000 Server [desktop apps only] |
| Header |
|
See also
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Reference
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Conceptual