How to get tooltip to not draw black rectangle on setting it's size on popup?

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all i want is a transparent (less opacity tool tip)

here is what I've so far

C#

public partial class CustomToolTip : ToolTip    
{
    public CustomToolTip()
    {
        InitializeComponent();
        this.BackColor = Color.FromArgb(127, 0, 0, 0);
        this.OwnerDraw = true;
        this.Popup += new PopupEventHandler(this.OnPopup);
        this.Draw += new DrawToolTipEventHandler(this.OnDraw);
    }

    protected override CreateParams CreateParams
    {
        get
        {
            CreateParams CP = base.CreateParams;
            CP.ExStyle = CP.ExStyle | 0x20;
            return CP;
        }
    }

    private void OnPopup(object sender, PopupEventArgs e)
    {
        e.ToolTipSize = new Size(200, 100);
    }

    private void OnDraw(object sender, DrawToolTipEventArgs e)
    {
        e.Graphics.FillRectangle(new SolidBrush(this.BackColor), e.Bounds);
    }
}

but i end up having a black rectangle at setting the tooltip size which i can't get ride of

any idea how could i draw without setting size or even remove that black rectangle ?

Posted 17-Aug-14 13:59pm

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Andrew Rober · Accepted Answer · 2014-08-18T00:05:00

answer by Loathing, maybe you folks wanna have a look how it was done

C#

public class CustomToolTip : ToolTip {
    public CustomToolTip() {
        this.BackColor = Color.FromArgb(127, 255, 0, 0);
        this.OwnerDraw = true;
        this.Popup += new PopupEventHandler(this.OnPopup);
        this.Draw += new DrawToolTipEventHandler(this.OnDraw);
    }

    private void OnPopup(Object sender, PopupEventArgs e) {
        e.ToolTipSize = new Size(200, 100);
        var window = typeof(ToolTip).GetField(&quot;window&quot;, BindingFlags.Instance | BindingFlags.NonPublic).GetValue(this) as NativeWindow;

        var Handle = window.Handle;
        SetWindowLong(Handle, GWL_EXSTYLE, GetWindowLong(Handle, GWL_EXSTYLE) ^ WS_EX_LAYERED);
        SetLayeredWindowAttributes(Handle, 0, 128, LWA_ALPHA);
    }

    public const int GWL_EXSTYLE = -20;
    public const int WS_EX_LAYERED = 0x80000;
    public const int LWA_ALPHA = 0x2;
    public const int LWA_COLORKEY = 0x1;

    [DllImport(&quot;user32.dll&quot;)]
    static extern bool SetLayeredWindowAttributes(IntPtr hwnd, uint crKey,byte bAlpha, uint dwFlags);
    [DllImport(&quot;user32.dll&quot;, SetLastError=true)]
    static extern int GetWindowLong(IntPtr hWnd, int nIndex);
    [DllImport(&quot;user32.dll&quot;)]
    static extern int SetWindowLong(IntPtr hWnd, int nIndex, int dwNewLong);

    private void OnDraw(object sender, DrawToolTipEventArgs e) {
        e.Graphics.FillRectangle(new SolidBrush(this.BackColor), e.Bounds);
        e.Graphics.DrawString(e.ToolTipText, e.Font, Brushes.Black, e.Bounds);
    }
}