在Windows窗体控件上使用RectVisible

Question

I'm trying to figure out if a windows forms control is visible to the user or is obstructed from view by another control or form (tabbed view). I have tried GetUpdateRect trick but it only works if the window is minimized. I found the RectVisible function, but am not sure how to use it from Windows Forms User control.

Thanks in Advance

Answer 1

I'm not sure what you mean by "Only works if the window is minimized". The solution with GetUpdateRect works:

[StructLayout(LayoutKind.Sequential)]
internal struct RECT
{
    public int Left;
    public int Top;
    public int Right;
    public int Bottom;
    public int Width { get { return this.Right - this.Left; } }
    public int Height { get { return this.Bottom - this.Top; } }
}

[DllImport("user32.dll")]
internal static extern bool GetUpdateRect(IntPtr hWnd, ref Rect rect, bool bErase);

public static bool IsControlVisibleToUser(Control control)
{
    control.Invalidate();
    var bounds = control.Bounds;
    var rect = new Rect {Left=bounds.Left, Right = bounds.Right, Top = bounds.Top, Bottom = bounds.Bottom};
    return GetUpdateRect(control.Handle, ref rect, false);
}