STM_SETIMAGE doesn't invalidate/repaint the static control

Question

Can anyone tell me if it's normal or not for a static control not to invalidate its area after the bitmap has been changed with the STM_SETIMAGE message?

I use a static control with the SS_BITMAP style, and I set its picture with the following code

    HBITMAP DestBmp;
    // Paint on DestBmp...

    HBITMAP hOldBmp = (HBITMAP) ::SendMessage(hStatic, STM_SETIMAGE, IMAGE_BITMAP, (LPARAM) DestBmp);
    if (hOldBmp)
        DeleteObject(hOldBmp);

    // *** Why do I need this? ***
    ::InvalidateRect(hStatic, NULL, FALSE);

If I don't call InvalidateRect, the static control doesn't repaint itself. Is this the normal behaviour of STM_SETIMAGE, or am I doing something wrong? The documentation at MSDN doesn't mention anything about needing to call InvalidateRect after STM_SETIMAGE, and its strange anyway, you don't need to call InvalidateRect after SetWindowText for example. This makes me think something might be wrong with my code.

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Update

This is how the control is defined in my .rc file

CONTROL         "",IDC_IMAGE_PREVIEW,"Static",SS_BITMAP | NOT WS_VISIBLE,29,293,15,13

The NOT WS_VISIBLE flag is not a problem, I make the control visible with ShowWindow(SW_SHOW); later.

Answer 1

Since there is no real explanation yet, and the question is getting views, I'll add my workaround here. Call InvalidateRect() to force the control to repaint.

HBITMAP hOldBmp = (HBITMAP) ::SendMessage(hStatic, STM_SETIMAGE, IMAGE_BITMAP, (LPARAM) DestBmp);
.....
::InvalidateRect(hStatic, NULL, FALSE);