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Overview
Group
Quick Info

Windows NT
Yes
Win95
Yes
Win32s
Yes
Import Library
user32.lib
Header File
winuser.h
Unicode
No
Platform Notes
None

SetWindowPos

The SetWindowPos function changes the size, position, and Z order of a child, pop-up, or top-level window. Child, pop-up, and top-level windows are ordered according to their appearance on the screen. The topmost window receives the highest rank and is the first window in the Z order.

BOOL SetWindowPos(

HWND hWnd,
// handle of window
HWND hWndInsertAfter,
// placement-order handle
int X,
// horizontal position
int Y,
// vertical position
int cx,
// width
int cy,
// height
UINT uFlags
// window-positioning flags
);

Parameters

hWnd

Identifies the window.

hWndInsertAfter

Identifies the window to precede the positioned window in the Z order. This parameter must be a window handle or one of the following values:

Value
Meaning
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.
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.
HWND_TOP
Places the window at the top of the Z order.
HWND_TOPMOST
Places the window above all non-topmost windows. The window maintains its topmost position even when it is deactivated.

For more information about how this parameter is used, see the following Remarks section.

X

Specifies the new position of the left side of the window.

Y

Specifies the new position of the top of the window.

cx

Specifies the new width of the window, in pixels.

cy

Specifies the new height of the window, in pixels.

uFlags

Specifies the window sizing and positioning flags. This parameter can be a combination of the following values:

Value
Meaning
SWP_DRAWFRAME
Draws a frame (defined in the window's class description) around the window.
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.
SWP_HIDEWINDOW
Hides the window.
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).
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.
SWP_NOMOVE
Retains the current position (ignores the X and Y parameters).
SWP_NOOWNERZORDER
Does not change the owner window's position in the Z order.
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.
SWP_NOREPOSITION
Same as the SWP_NOOWNERZORDER flag.
SWP_NOSENDCHANGING
Prevents the window from receiving the WM_WINDOWPOSCHANGING message.
SWP_NOSIZE
Retains the current size (ignores the cx and cy parameters).
SWP_NOZORDER
Retains the current Z order (ignores the hWndInsertAfter parameter).
SWP_SHOWWINDOW
Displays the window.

Return Values

If the function succeeds, the return value is nonzero.

If the function fails, the return value is zero. To get extended error information, call GetLastError.

Remarks

If the SWP_SHOWWINDOW or SWP_HIDEWINDOW flag is set, the window cannot be moved or sized.

All coordinates for child windows are client coordinates (relative to the upper-left corner of the parent window's client area).

A window can be made a topmost window either by setting the hWndInsertAfter parameter to HWND_TOPMOST and ensuring that the SWP_NOZORDER flag is not set, or by setting a 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:

  • Neither the HWND_TOPMOST nor HWND_NOTOPMOST flag is specified in hWndInsertAfter.

  • The window identified by hWnd is not the active window.

An application cannot activate an inactive window without also bringing it to the top of the Z order. Applications 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.

If a topmost window is repositioned to the bottom (HWND_BOTTOM) of the Z order or after any non-topmost window, it is no longer topmost. When a topmost window is made non-topmost, its owners and its owned windows are also made non-topmost windows.

A non-topmost window can own a topmost window, but the reverse cannot occur. 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.

If an application is not in the foreground, and should be in the foreground, it must call the SetForegroundWindow function.

See Also

MoveWindow
, SetActiveWindow, SetForegroundWindow

Comment from Greatis Sofware

Have you ever been in situation, when the window redraws whenever it wants (most often, when system idles), while you need to make it redraw in definite moment? First time when I faced this problem, I've tried everything. Of course, i've tried all, that is related to window redraw: RedrawWindow, UpdateWindow, InvalidateRect, WM_PAINT and even WM_ERASEBKGND. In a word, i've tried everything from "Painting and Drawing Functions" and "Painting and Drawing Messages" groups. Everything was unhelpful. I even tried to hide and then show the window, but it didn't redraw it... I was close to blank despair, and I thought, that there's only one way - to free the window, and then to create it again when I got the sense, that I've seen something about redraw in topic, that is not related with drawing. I've searched last changes to source code, and found SetWindowPos function. This function has SWP_NOREDRAW flag, which I haven't used. Obviously, this flag denies window redraw on operations, that SetWindowPos function execute. I arrived at an idea, to deny all operations but redraw. Quickly I wrote something like...

SetWindowPos( my_window_handle, 0, 0, 0, 0, SWP_NOMOVE | SWP_NOSIZE |
SWP_NOZORDER );
...and my window did redraw! Still, it's the only way, that I know, to redraw window immediatly, and not to wait, until idle system start to query all windows, and to ask them, if they want to make some updates. By the way, big amount of flags, makes me thing, that useful side effects of SetWindowPos function do not exhaust with redraw... Do you want to experiment on this?


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