WM_NCHITTEST

#include <windows.h>

LRESULT CALLBACK WndProc(HWND,UINT,WPARAM,LPARAM);
HINSTANCE g_hInst;
HWND hWndMain;
LPSTR lpszClass="NcHitTest";

int APIENTRY WinMain(HINSTANCE hInstance,HINSTANCE hPrevInstance
     ,LPSTR lpszCmdParam,int nCmdShow)
{
    HWND hWnd;
    MSG Message;
    WNDCLASS WndClass;
    g_hInst=hInstance;
    
    WndClass.cbClsExtra=0;
    WndClass.cbWndExtra=0;
    WndClass.hbrBackground=(HBRUSH)GetStockObject(WHITE_BRUSH);
    WndClass.hCursor=LoadCursor(NULL,IDC_ARROW);
    WndClass.hIcon=LoadIcon(NULL,IDI_APPLICATION);
    WndClass.hInstance=hInstance;
    WndClass.lpfnWndProc=(WNDPROC)WndProc;
    WndClass.lpszClassName=lpszClass;
    WndClass.lpszMenuName=NULL;
    WndClass.style=CS_HREDRAW | CS_VREDRAW;
    RegisterClass(&WndClass);

    hWnd=CreateWindow(lpszClass,lpszClass,WS_OVERLAPPEDWINDOW,
        CW_USEDEFAULT,CW_USEDEFAULT,CW_USEDEFAULT,CW_USEDEFAULT,
        NULL,(HMENU)NULL,hInstance,NULL);
    ShowWindow(hWnd,nCmdShow);
    hWndMain=hWnd;
    
    while(GetMessage(&Message,0,0,0)) {
        TranslateMessage(&Message);
        DispatchMessage(&Message);
    }
    return Message.wParam;
}

LRESULT CALLBACK WndProc(HWND hWnd,UINT iMessage,WPARAM wParam,LPARAM lParam)
{
    HDC hdc;
    PAINTSTRUCT ps;
    RECT crt;
    int i;
    int nHit;
    POINT mpt;        // 마우스 위치 값을 저장하기 위한 struct    
    char Mes[]="WM_NCHITTEST 메시지를 활용하는 예제입니다";

    switch(iMessage) {
    case WM_CREATE:
        return 0;
    case WM_PAINT:
        hdc=BeginPaint(hWnd, &ps);
        GetClientRect(hWnd,&crt);            // 윈도우 크기 변경시 값을 lParam에 전달
        
        for (i=50;i>0;i-=5) {                // 윈도우 크기를 조정 할 수 있는 라인을 그리기
            MoveToEx(hdc,crt.right, crt.bottom-i,NULL);
            LineTo(hdc,crt.right-i,crt.bottom);
        }
        TextOut(hdc,10,10,Mes,strlen(Mes));
        EndPaint(hWnd, &ps);
        return 0;
    case WM_NCHITTEST:
        GetClientRect(hWnd,&crt);            // 윈도우 크기 변경시 값을 lParam에 전달
        mpt.x=LOWORD(lParam);
        mpt.y=HIWORD(lParam);
        ScreenToClient(hWnd,&mpt);
        if (mpt.y > -mpt.x -50 + crt.right+crt.bottom) {
            nHit=HTBOTTOMRIGHT;
        } else {
            nHit=DefWindowProc(hWnd,iMessage,wParam,lParam);
            switch (nHit) {
            case HTCLIENT:
                nHit=HTCAPTION;
                break;
            case HTLEFT:
                nHit=HTMAXBUTTON;
                break;
            case HTMINBUTTON:
                nHit=HTCLOSE;
                break;
            case HTMAXBUTTON:
                nHit=HTMINBUTTON;
                break;
            case HTCLOSE:
                nHit=HTLEFT;
                break;
            }
        }
        return nHit;
    case WM_DESTROY:
        PostQuitMessage(0);
        return 0;
    }
    return(DefWindowProc(hWnd,iMessage,wParam,lParam));
}