如何在窗口周围绘制矩形而不覆盖Win32中的标题栏

Question

I want to draw a rectangle around my window but I don't want to override the title bar. what I wrote so far in the window callback function is:

    case WM_NCPAINT:
    {
        HDC hdc;
        RECT rect;
        HPEN pen;

        hdc=GetDCEx(hWnd,(HRGN)wParam,DCX_WINDOW|DCX_CACHE|DCX_INTERSECTRGN|DCX_LOCKWINDOWUPDATE);
        GetWindowRect(hWnd,&rect);
        pen=CreatePen(PS_SOLID, 10, RGB(255, 0, 0));//red pen 10 pixels in size
        SelectObject(hdc,pen);
        Rectangle(hdc,0,0,(rect.right-rect.left),(rect.bottom-rect.top));
        DeleteObject(pen);
        ReleaseDC(hWnd,hdc);
    }
    break;

However, this draws over the window title bar with white brush.

How can I make it not to paint over the title bar? I'm loosing the title bar text and the menu...

I have tried using HOLLOW_BRUSH before creating the pen as follows:

        HBRUSH b=CreateSolidBrush(HOLLOW_BRUSH);
        SelectObject(hdc,b);

But that only caused the title bar to not be drawn at all (being black).

Answer 1

By handling the WM_NCPAINT message, you are telling the window manager that you are taking responsibility for painting the entire non-client area, and so the window manager will not draw any of it for you.

If you want the original title bar to be drawn then you need to call DefWindowProc() first, then do your own drawing "on top" of what it draws.

You may also need to use ExcludeClipRect() to prevent the client area from being drawn over if you wish to draw the entire non-client area at once with a single rectangle.