The DeferWindowPos function updates the specified multiple-window - position structure for the specified window. The function then returns the handle to the updated structure. The EndDeferWindowPos function uses the information in this structure to change the position and size of a number of windows simultaneously. The BeginDeferWindowPos function creates the structure.
HDWP DeferWindowPos(
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HDWP hWinPosInfo, |
// handle to internal structure |
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HWND hWnd, |
// handle to window to position |
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HWND hWndInsertAfter, |
// placement-order handle |
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int x, |
// horizontal position |
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int y, |
// vertical position |
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int cx, |
// width |
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int cy, |
// height |
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UINT uFlags |
// window-positioning flags |
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); |
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Value |
Meaning |
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HWND_BOTTOM |
Places the window at the bottom of the Z order. If the hWnd parameter identifies a topmost window, the window loses its topmost status and is placed at the bottom of all other windows. |
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HWND_NOTOPMOST |
Places the window above all non-topmost windows (that is, behind all topmost windows). This flag has no effect if the window is already a non-topmost window. |
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HWND_TOP |
Places the window at the top of the Z order. |
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HWND_TOPMOST |
Places the window above all non-topmost windows. The window maintains its topmost position even when it is deactivated. |
This parameter is ignored if the SWP_NOZORDER flag is set in the uFlags
parameter.
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Value |
Meaning |
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SWP_DRAWFRAME |
Draws a frame (defined in the window’s class description) around the window. |
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SWP_FRAMECHANGED |
Sends a WM_NCCALCSIZE message to the window, even if the window’s size is not being changed. If this flag is not specified, WM_NCCALCSIZE is sent only when the window’s size is being changed. |
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SWP_HIDEWINDOW |
Hides the window. |
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SWP_NOACTIVATE |
Does not activate the window. If this flag is not set, the window is activated and moved to the top of either the topmost or non-topmost group (depending on the setting of the hWndInsertAfter parameter). |
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SWP_NOCOPYBITS |
Discards the entire contents of the client area. If this flag is not specified, the valid contents of the client area are saved and copied back into the client area after the window is sized or repositioned. |
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SWP_NOMOVE |
Retains the current position (ignores the X and Y parameters). |
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SWP_NOOWNERZORDER |
Does not change the owner window’s position in the Z order. |
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SWP_NOREDRAW |
Does not redraw changes. If this flag is set, no repainting of any kind occurs. This applies to the client area, the nonclient area (including the title bar and scroll bars), and any part of the parent window uncovered as a result of the window being moved. When this flag is set, the application must explicitly invalidate or redraw any parts of the window and parent window that need redrawing. |
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SWP_NOREPOSITION |
Same as the SWP_NOOWNERZORDER flag. |
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SWP_NOSENDCHANGING |
Prevents the window from receiving the WM_WINDOWPOSCHANGING message. |
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SWP_NOSIZE |
Retains the current size (ignores the cx and cy parameters). |
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SWP_NOZORDER |
Retains the current Z order (ignores the hWndInsertAfter parameter). |
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SWP_SHOWWINDOW |
Displays the window. |
The return value identifies the updated multiple-window - position structure. The handle returned by this function may differ from the handle passed to the function. The new handle that this function returns should be passed during the next call to the DeferWindowPos or EndDeferWindowPos function.
If insufficient system resources are available for the function to succeed, the return value is NULL. To get extended error information, call GetLastError.
If a call to DeferWindowPos fails, the application should abandon the window-positioning operation and not call EndDeferWindowPos.
If SWP_NOZORDER is not specified, Windows places the window identified by the hWnd parameter in the position following the window identified by the hWndInsertAfter parameter. If hWndInsertAfter is NULL or HWND_TOP, Windows places the hWnd window at the top of the Z order. If hWndInsertAfter is set to HWND_BOTTOM, Windows places the hWnd window at the bottom of the Z order.
All coordinates for child windows are relative to the upper-left corner of the parent window’s client area.
A window can be made a topmost window either by setting hWndInsertAfter to the HWND_TOPMOST flag and ensuring that the SWP_NOZORDER flag is not set, or by setting the window’s position in the Z order so that it is above any existing topmost windows. When a non-topmost window is made topmost, its owned windows are also made topmost. Its owners, however, are not changed.
If neither the SWP_NOACTIVATE nor SWP_NOZORDER flag is specified (that is, when the application requests that a window be simultaneously activated and its position in the Z order changed), the value specified in hWndInsertAfter is used only in the following circumstances:
An application cannot activate an inactive window without also bringing it to the top of the Z order. An application can change an activated window’s position in the Z order without restrictions, or it can activate a window and then move it to the top of the topmost or non-topmost windows.
A topmost window is no longer topmost if it is repositioned to the bottom (HWND_BOTTOM) of the Z order or after any non-topmost window. When a topmost window is made non-topmost, its owners and its owned windows are also made non-topmost windows.
A non-topmost window may own a topmost window, but not vice versa. Any window (for example, a dialog box) owned by a topmost window is itself made a topmost window to ensure that all owned windows stay above their owner.