Перемещение окна и получение координат центра окна

#include "windows.h"
LONG WinProcMain(HWND,UINT,WPARAM,LPARAM);
BOOL RegWinClass(WNDPROC, LPCTSTR, UINT);
 
HINSTANCE hInst;
wchar_t ClassNameMain[] = L"Disc Format";
int height = 100, width = 200;
int Horres, Vertress;
 
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrervInstance, LPSTR lpCmdLine, int nCmdShow)
{
    HWND hWnd;
    MSG msg;
    hInst = hInstance;
 
    if (!RegWinClass((WNDPROC)WinProcMain, ClassNameMain, COLOR_WINDOW)) return false;
 
    HDC hDCScreen = GetDC(NULL);
    Horres = GetDeviceCaps(hDCScreen, HORZRES) / 4;
    Vertress = GetDeviceCaps(hDCScreen, VERTRES) / 5;
 
    hWnd = CreateWindow(ClassNameMain,L"Disc Format",WS_OVERLAPPEDWINDOW|WS_VISIBLE,CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT
        , CW_USEDEFAULT,NULL,NULL,hInstance,NULL);
    
    while (GetMessage(&msg, NULL, 0, 0))
        DispatchMessage(&msg);
    return int(msg.wParam);
}
 
BOOL RegWinClass(WNDPROC proc, LPCTSTR lpszClassName, UINT hrBackGround)
{
    WNDCLASS w;
    w.lpszClassName = lpszClassName;
    w.hInstance = hInst;
    w.lpfnWndProc = proc;
    w.hCursor = LoadCursor(NULL, IDC_ARROW);
    w.hIcon = LoadIcon(NULL, lpszClassName);
    w.lpszMenuName = NULL;
    w.hbrBackground = (HBRUSH)(hrBackGround + 1);
    w.style = CS_HREDRAW | CS_VREDRAW;
    w.cbClsExtra = 0;
    w.cbWndExtra = 0;
    return (RegisterClass(&w) != 0);
}
 
LONG WinProcMain(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
    RECT rct;
    switch (msg)
    {
    case WM_MOUSEMOVE:
        POINT p;
        GetCursorPos(&p);
        MoveWindow(hWnd,p.x,p.y,width,height,TRUE);
        break;
    case WM_LBUTTONDOWN:
        POINT cp;
        if (GetWindowRect(hWnd, &rct) == GetCursorPos(&cp))
        {
            MoveWindow(hWnd, cp.x, cp.y, width, height, TRUE);
        }
        break;
    case WM_DESTROY:
            PostQuitMessage(0);
            break;
    default:
        return LONG(DefWindowProc(hWnd, msg, wParam, lParam));
    }
}