수다닷컴

안녕하세요
윈도우즈API 책을 보고 공부하고 있는 중인데요.
질문이 있습니다.

우선 프로그램을 실행을 하면 자유곡선/선/원/사각형 을 메뉴에서 선택해서
마우스를 누르고 움직이면 움직이는데로 선택한 도형이 그려지는 건데요.

자유곡선을 제외한 나머지는 다 잔상이 남아서 아래 그림처럼 되네요.
WndProc 는 아래와 같습니다.LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
int wmId, wmEvent;
PAINTSTRUCT ps;
HDC hdc;
static int sx, sy, oldx, oldy;
static BOOL bNowDraw = FALSE;
static int DrawMode;
HBRUSH MyBrush, OldBrush;
HPEN MyPen, OldPen;
switch (message)
{
case WM_COMMAND:
wmId = LOWORD(wParam);
wmEvent = HIWORD(wParam);
// 메뉴의 선택 영역을 구문 분석합니다.
switch (wmId)
{
case IDM_ABOUT:
DialogBox(hInst, MAKEINTRESOURCE(IDD_ABOUTBOX), hWnd, About);
break;
case IDM_EXIT:
DestroyWindow(hWnd);
break;
case ID_Mode_FreeLine:
DrawMode = ROP_FREELINE;
break;
case ID_Mode_Line:
DrawMode = ROP_LINE;
break;
case ID_Mode_Circle:
DrawMode = ROP_CIRCLE;
break;
case ID_Mode_Rectangle:
DrawMode = ROP_RECTANGLE;
break;
default:
return DefWindowProc(hWnd, message, wParam, lParam);
}
break;
case WM_LBUTTONDOWN:
sx = LOWORD(lParam);
sy = HIWORD(lParam);
oldx = sx;
oldy = sy;
bNowDraw = TRUE;
return 0;
case WM_MOUSEMOVE:
if(bNowDraw) {
hdc = GetDC(hWnd);
SetROP2(hdc, R2_COPYPEN);
switch(DrawMode)
{
case ROP_FREELINE:
MoveToEx(hdc, sx, sy, NULL);
p; sx = LOWORD(lParam);
sy = HIWORD(lParam);
LineTo(hdc, sx, sy);
break;
case ROP_LINE:
SetROP2(hdc, R2_NOT);
MoveToEx(hdc, sx, sy, NULL);
LineTo(hdc, oldx, oldy);
oldx = LOWORD(lParam);
oldy = HIWORD(lParam);
MoveToEx(hdc, sx, sy, NULL);
LineTo(hdc, oldx, oldy);
break;
case ROP_CIRCLE:
oldx = LOWORD(lParam);
oldy = HIWORD(lParam);

Ellipse(hdc, sx, sy, oldx, oldy);
break;
case ROP_RECTANGLE:
MyBrush = CreateSolidBrush(RGB(255, 255, 0));
OldBrush = (HBRUSH)SelectObject(hdc, MyBrush);
MyPen = CreatePen(PS_DASH, 3, RGB(255, 0, 255));
OldPen = (HPEN)SelectObject(hdc, MyPen);
oldx = LOWORD(lParam);
oldy = HIWORD(lParam);
Rectangle(hdc, sx, sy, oldx, oldy);
DeleteObject(SelectObject(hdc, OldPen));
DeleteObject(SelectObject(hdc, OldBrush));
break;
}
ReleaseDC(hWnd, hdc);
}
return 0;
case WM_LBUTTONUP:
bNowDraw = FALSE;
if(DrawMode == ROP_LINE) {
hdc = GetDC(hWnd);
&nbsbsp; MoveToEx(hdc, sx, sy, NULL);
LineTo(hdc, oldx, oldy);
ReleaseDC(hWnd, hdc);
}
return 0;
case WM_DESTROY:
PostQuitMessage(0);
break;
default:
return DefWindowProc(hWnd, message, wParam, lParam);
}
return 0;
}처음 공부하는거라 잘 모르겠습니다.

답변 부탁드릴게요.
감사합니다.

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