선그리기 (line)

#include <windows.h>

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

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);
    
    while(GetMessage(&Message,0,0,0)) {
        TranslateMessage(&Message);
        DispatchMessage(&Message);
    }
    return Message.wParam;
}

LRESULT CALLBACK WndProc(HWND hWnd,UINT iMessage,WPARAM wParam,LPARAM lParam)
{
    static int sx,sy,oldx,oldy;
    int ex,ey;
    static BOOL bNowDraw = FALSE;
    HDC hdc;
    switch(iMessage) {
    case WM_DESTROY:
        PostQuitMessage(0);
        return 0;
    case WM_LBUTTONDOWN:
        sx = LOWORD(lParam);
        sy = HIWORD(lParam);
        oldx = sx;
        oldy = sy;
        bNowDraw = TRUE;
        return 0;
    case WM_LBUTTONUP:
        bNowDraw = FALSE;
        hdc=GetDC(hWnd);
        MoveToEx(hdc,sx,sy,NULL);
        LineTo(hdc,oldx,oldy);
        ReleaseDC(hWnd, hdc);
        return 0;
    case WM_MOUSEMOVE:
        if (bNowDraw) {
            hdc=GetDC(hWnd);
            SetROP2(hdc,R2_NOT);
            MoveToEx(hdc,sx,sy,NULL);
            LineTo(hdc,oldx,oldy);
            ex = LOWORD(lParam);
            ey = HIWORD(lParam);
            MoveToEx(hdc,sx,sy,NULL);
            LineTo(hdc,ex,ey);
            oldx = ex;
            oldy = ey;
            ReleaseDC(hWnd,hdc);
        }
        return 0;
    }
    return(DefWindowProc(hWnd,iMessage,wParam,lParam));
}