API函数之一 SetWindowPos

 

SetWindowPos Function

Changesthe size, position, and Z order of a child, pop-up, or top-levelwindow. These windows are ordered according to their appearance on thescreen. The topmost window receives the highest rank and is the firstwindow in the Z order.

Syntax：

1. BOOL SetWindowPos(      
2.     HWND hWnd,
3.     HWND hWndInsertAfter,
4.     int X,
5.     int Y,
6.     int cx,
7.     int cy,
8.     UINT uFlags
9. );

Parameters

hWnd

[in] A handle to the window.

hWndInsertAfter

[in] A handle to the window to precede the positioned window in the Zorder. This parameter must be a window handle or one of the followingvalues.

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

Placesthe window above all non-topmost windows (that is, behind all topmostwindows). This flag has no effect if the window is already anon-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

[in] Specifies the new position of the left side of the window, in client coordinates.

Y

[in] Specifies the new position of the top of the window, in client coordinates.

cx

[in] Specifies the new width of the window, in pixels.

cy

[in] Specifies the new height of the window, in pixels.

uFlags

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

SWP_ASYNCWINDOWPOS

Ifthe calling thread and the thread that owns the window are attached todifferent input queues, the system posts the request to the thread thatowns the window. This prevents the calling thread from blocking itsexecution while other threads process the request.

SWP_DEFERERASE

Prevents generation of the WM_SYNCPAINT message.

SWP_DRAWFRAME

Draws a frame (defined in the window's class description) around the window.

SWP_FRAMECHANGED

Applies new frame styles set using the SetWindowLong function. 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

Doesnot activate the window. If this flag is not set, the window isactivated and moved to the top of either the topmost or non-topmostgroup (depending on the setting of the hWndInsertAfter parameter).

SWP_NOCOPYBITS

Discardsthe entire contents of the client area. If this flag is not specified,the valid contents of the client area are saved and copied back intothe client area after the window is sized or repositioned.

SWP_NOMOVE

Retains the current position (ignores X and Y parameters).

SWP_NOOWNERZORDER

Does not change the owner window's position in the Z order.

SWP_NOREDRAW

Doesnot redraw changes. If this flag is set, no repainting of any kindoccurs. This applies to the client area, the nonclient area (includingthe title bar and scroll bars), and any part of the parent windowuncovered as a result of the window being moved. When this flag is set,the application must explicitly invalidate or redraw any parts of thewindow 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 Value

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

Aspart of the Vista re-architecture, all services were moved off theinteractive desktop into Session 0. hwnd and window manager operationsare only effective inside a session and cross-session attempts tomanipulate the hwnd will fail. For more information, see Session 0 Isolation.

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

If you have changed certain window data using SetWindowLong, you must call SetWindowPos for the changes to take effect. Use the following combination for uFlags: SWP_NOMOVE | SWP_NOSIZE | SWP_NOZORDER | SWP_FRAMECHANGED.

A window can be made a topmost window either by setting the hWndInsertAfterparameter to HWND_TOPMOST and ensuring that the SWP_NOZORDER flag isnot set, or by setting a window's position in the Z order so that it isabove any existing topmost windows. When a non-topmost window is madetopmost, its owned windows are also made topmost. Its owners, however,are not changed.

If neither the SWP_NOACTIVATE nor SWP_NOZORDERflag is specified (that is, when the application requests that a windowbe 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.

Anapplication cannot activate an inactive window without also bringing itto the top of the Z order. Applications can change an activatedwindow's position in the Z order without restrictions, or it canactivate a window and then move it to the top of the topmost ornon-topmost windows.

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

Anon-topmost window can own a topmost window, but the reverse cannotoccur. Any window (for example, a dialog box) owned by a topmost windowis itself made a topmost window, to ensure that all owned windows stayabove their owner.

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

To use SetWindowPos to bring a window to the top, the process that owns the window must have SetForegroundWindow permission.

虽然是MSDN中的原话，不过我觉得讲的很清晰了，每次把我用到的API函数收集起来也是一件有意义的事情