Source code of Windows XP (NT5)
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//+---------------------------------------------------------------------------
//
// Microsoft Windows
// Copyright (C) Microsoft Corporation, 1997.
//
// File: W I N D U T I L . C P P
//
// Contents: Window utilities -- For now, just CenterWindow
//
// Notes:
//
// Author: jeffspr 22 May 1998
//
//----------------------------------------------------------------------------
#include "pch.h"
#pragma hdrstop
//+---------------------------------------------------------------------------
//
// Function: FCenterWindow
//
// Purpose: Center a child window on the parent
//
// Arguments:
// hwndChild [in] Child window handle
// hwndParent [in] Parent window handle (or NULL for desktop)
//
// Returns:
//
// Author: jeffspr 22 May 1998
//
// Notes:
//
BOOL FCenterWindow (HWND hwndChild, HWND hwndParent)
{
RECT rChild, rParent;
int wChild, hChild, wParent, hParent;
int wScreen, hScreen, xNew, yNew;
HDC hdc = NULL;
BOOL fReturn = TRUE;
AssertSz(hwndChild, "Bad Child Window param to CenterWindow");
// Get the Height and Width of the child window
//
GetWindowRect (hwndChild, &rChild);
wChild = rChild.right - rChild.left;
hChild = rChild.bottom - rChild.top;
// Get the Height and Width of the parent window
//
if (NULL == hwndParent)
{
GetWindowRect (GetDesktopWindow(), &rParent);
}
else
{
GetWindowRect (hwndParent, &rParent);
}
wParent = rParent.right - rParent.left;
hParent = rParent.bottom - rParent.top;
// Get the display limits
//
hdc = GetDC (hwndChild);
if (hdc)
{
wScreen = GetDeviceCaps (hdc, HORZRES);
hScreen = GetDeviceCaps (hdc, VERTRES);
ReleaseDC (hwndChild, hdc);
// Calculate new X position, then adjust for screen
//
xNew = rParent.left + ((wParent - wChild) / 2);
if (xNew < 0)
{
xNew = 0;
}
else if ((xNew + wChild) > wScreen)
{
xNew = wScreen - wChild;
}
// Calculate new Y position, then adjust for screen
//
yNew = rParent.top + ((hParent - hChild) / 2);
if (yNew < 0)
{
yNew = 0;
}
else if ((yNew + hChild) > hScreen)
{
yNew = hScreen - hChild;
}
// Set it, and return
//
fReturn = SetWindowPos (hwndChild, NULL,
xNew, yNew, 0, 0, SWP_NOSIZE | SWP_NOZORDER);
}
else
{
fReturn = FALSE;
}
return fReturn;
}