BeginDeferWindowPos (Windows CE 5.0)

项目
09/14/2012

This function allocates memory for a multiple-window position structure and returns the handle to the structure.

HDWP BeginDeferWindowPos(   int nNumWindows );

Parameters

nNumWindows
[in] Specifies the initial number of windows for which to store position information. The DeferWindowPos function increases the size of the structure, if necessary.

Return Values

If the function succeeds, the return value identifies the multiple-window — position structure. NULL indicates that insufficient system resources are available to allocate the structure. To get extended error information, call GetLastError.

Code Example

Here, BeginDeferWindowPos is used to get information in order to update a window.

void DXView_OnSize(HWND hWnd)
{
    HDWP hDWP;
    RECT ClientRect;
    int Height;
    HWND hKeyTreeWnd, hValueListWnd;
    int x;
    int dx;

    if ((hDWP =  BeginDeferWindowPos (2)) != NULL)
    {
        GetClientRect(hWnd, &ClientRect);
...
}

Remarks

The multiple-window — position structure is an internal structure; an application cannot access it directly.

DeferWindowPos fills the multiple-window — position structure with information about the target position for one or more windows about to be moved. The EndDeferWindowPos function accepts the handle to this structure and repositions the windows by using the information stored in the structure.

If any of the windows in the multiple-window — position structure have the SWP_HIDEWINDOW or SWP_SHOWWINDOW flag set, none of the windows are repositioned.

If the system must increase the size of the multiple-window — position structure beyond the initial size specified by the nNumWindows parameter but cannot allocate enough memory to do so, the system fails the entire window positioning sequence (BeginDeferWindowPos, DeferWindowPos, and EndDeferWindowPos). By specifying the maximum size needed, an application can detect and process failure early in the process.

Requirements

OS Versions: Windows CE 2.10 and later.
Header: Winuser.h.

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