C#: Set position of the arrow in a ToolTip Balloon?

Question

Is it possible to change the location of the Arrow / Stem in a Balloon Tooltip? Reason to change is because of a Button, located in the top of the screen, should have a too

Answer 1

I used InteropServices to call several User32.dll methods (CreateWindowEx, DestroyWindow, SetWindowPos and SendMessage) to use native Win32 tooltips instead of the WinForms-provided wrapper.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Runtime.InteropServices;
using System.Drawing;
using System.ComponentModel;

/// This classes implements the balloon tooltip.
/// http://stackoverflow.com/questions/2028466
/// I hated Microsoft WinForms QA department after I had to develop my own version of the tooltip class,
/// just to workaround a bug, that would only add ~5 lines of code into the system.windows.forms.dll when fixed properly.
class BalloonToolTip : IDisposable
{
    #region Unmanaged shit

    [DllImport( "user32.dll" )]
    static extern IntPtr CreateWindowEx( int exstyle, string classname, string windowtitle,
        int style, int x, int y, int width, int height, IntPtr parent,
        int menu, int nullvalue, int nullptr );

    [DllImport( "user32.dll" )]
    static extern int DestroyWindow( IntPtr hwnd );

    [DllImport( "user32.dll" )]
    static extern bool SetWindowPos( IntPtr hWnd, IntPtr hWndInsertAfter, int X, int Y, int cx, int cy, int uFlags );

    [DllImport( "user32.dll" )]
    static extern int SendMessage( IntPtr hWnd, int Msg, int wParam, IntPtr lParam );

    const int WS_POPUP = unchecked( (int)0x80000000 );
    const int TTS_BALLOON = 0x40;
    const int TTS_NOPREFIX = 0x02;
    const int TTS_ALWAYSTIP = 0x01;

    const int CW_USEDEFAULT = unchecked( (int)0x80000000 );

    const int WM_USER = 0x0400;

    IntPtr HWND_TOPMOST = new IntPtr( -1 );

    const int SWP_NOSIZE = 0x0001;
    const int SWP_NOMOVE = 0x0002;
    const int SWP_NOACTIVATE = 0x0010;

    const int WS_EX_TOPMOST = 0x00000008;

    [StructLayout( LayoutKind.Sequential )]
    public struct TOOLINFO
    {
        public int cbSize;
        public int uFlags;
        public IntPtr hwnd;
        public IntPtr id;
        private RECT m_rect;
        public IntPtr nullvalue;
        [MarshalAs( UnmanagedType.LPTStr )]
        public string text;
        public uint param;

        public Rectangle rect
        {
            get
            {
                return new Rectangle( m_rect.left, m_rect.top, m_rect.right - m_rect.left, m_rect.bottom - m_rect.top );
            }
            set
            {
                m_rect.left = value.Left;
                m_rect.top = value.Top;
                m_rect.right = value.Right;
                m_rect.bottom = value.Bottom;
            }
        }
    }

    [StructLayout( LayoutKind.Sequential )]
    struct RECT
    {
        public int left;
        public int top;
        public int right;
        public int bottom;
    }

    const int TTF_TRANSPARENT = 0x0100;
    const int TTF_TRACK = 0x0020;
    const int TTF_ABSOLUTE = 0x0080;

    #endregion

    #region Managed wrapper over some tooltip messages.
    // The most useful part of the wrappers in this section is their documentation.

    /// 
Send TTM_SETTITLE message to the tooltip.
    /// TODO [very low]: implement the custom icon, if needed. 
    /// HWND of the tooltip
    /// Standard icon
    /// The title string
    internal static int SetTitle( IntPtr _wndTooltip, ToolTipIcon _icon, string _title )
    {
        const int TTM_SETTITLE = WM_USER + 33;

        var tempptr = IntPtr.Zero;
        try
        {
            tempptr = Marshal.StringToHGlobalUni( _title );
            return SendMessage( _wndTooltip, TTM_SETTITLE, (int)_icon, tempptr );
        }
        finally
        {
            if( IntPtr.Zero != tempptr )
            {
                Marshal.FreeHGlobal( tempptr );
                tempptr = IntPtr.Zero;
            }
        }
    }

    /// 
Send a message that wants LPTOOLINFO as the lParam
    /// HWND of the tooltip.
    /// window message to send
    /// wParam value
    /// TOOLINFO structure that goes to the lParam field. The cbSize field must be set.
    internal static int SendToolInfoMessage( IntPtr _wndTooltip, int _msg, int _wParam, TOOLINFO _ti )
    {
        var tempptr = IntPtr.Zero;
        try
        {
            tempptr = Marshal.AllocHGlobal( _ti.cbSize );
            Marshal.StructureToPtr( _ti, tempptr, false );

            return SendMessage( _wndTooltip, _msg, _wParam, tempptr );
        }
        finally
        {
            if( IntPtr.Zero != tempptr )
            {
                Marshal.FreeHGlobal( tempptr );
                tempptr = IntPtr.Zero;
            }
        }
    }

    /// 
Registers a tool with a ToolTip control
    /// HWND of the tooltip
    /// TOOLINFO structure containing information that the ToolTip control needs to display text for the tool.
    /// Returns true if successful.
    internal static bool AddTool( IntPtr _wndTooltip, TOOLINFO _ti )
    {
        const int TTM_ADDTOOL = WM_USER + 50;
        int res = SendToolInfoMessage( _wndTooltip, TTM_ADDTOOL, 0, _ti );
        return Convert.ToBoolean( res );
    }

    /// 
Registers a tool with a ToolTip control
    /// HWND of the tooltip
    /// TOOLINFO structure containing information that the ToolTip control needs to display text for the tool.
    internal static void DelTool( IntPtr _wndTooltip, TOOLINFO _ti )
    {
        const int TTM_DELTOOL = WM_USER + 51;
        SendToolInfoMessage( _wndTooltip, TTM_DELTOOL, 0, _ti );
    }

    internal static void UpdateTipText( IntPtr _wndTooltip, TOOLINFO _ti )
    {
        const int TTM_UPDATETIPTEXT = WM_USER + 57;
        SendToolInfoMessage( _wndTooltip, TTM_UPDATETIPTEXT, 0, _ti );
    }

    /// 
Activates or deactivates a tracking ToolTip
    /// HWND of the tooltip
    /// Value specifying whether tracking is being activated or deactivated
    /// Pointer to a TOOLINFO structure that identifies the tool to which this message applies
    internal static void TrackActivate( IntPtr _wndTooltip, bool bActivate, TOOLINFO _ti )
    {
        const int TTM_TRACKACTIVATE = WM_USER + 17;
        SendToolInfoMessage( _wndTooltip, TTM_TRACKACTIVATE, Convert.ToInt32( bActivate ), _ti );
    }

    /// 
returns (LPARAM) MAKELONG( pt.X, pt.Y )
    internal static IntPtr makeLParam( Point pt )
    {
        int res = ( pt.X & 0xFFFF );
        res |= ( ( pt.Y & 0xFFFF ) << 16 );
        return new IntPtr( res );
    }

    /// 
Sets the position of a tracking ToolTip
    /// HWND of the tooltip.
    /// The point at which the tracking ToolTip will be displayed, in screen coordinates.
    internal static void TrackPosition( IntPtr _wndTooltip, Point pt )
    {
        const int TTM_TRACKPOSITION = WM_USER + 18;
        SendMessage( _wndTooltip, TTM_TRACKPOSITION, 0, makeLParam( pt ) );
    }

    /// 
Sets the maximum width for a ToolTip window
    /// HWND of the tooltip.
    /// Maximum ToolTip window width, or -1 to allow any width
    /// the previous maximum ToolTip width
    internal static int SetMaxTipWidth( IntPtr _wndTooltip, int pxWidth )
    {
        const int TTM_SETMAXTIPWIDTH = WM_USER + 24;
        return SendMessage( _wndTooltip, TTM_SETMAXTIPWIDTH, 0, new IntPtr( pxWidth ) );
    }

    #endregion

    /// 
Sets the information that a ToolTip control maintains for a tool (not currently used).
    /// 
    internal void AlterToolInfo( Action act )
    {
        const int TTM_GETTOOLINFO = WM_USER + 53;
        const int TTM_SETTOOLINFO = WM_USER + 54;

        var tempptr = IntPtr.Zero;
        try
        {
            tempptr = Marshal.AllocHGlobal( m_toolinfo.cbSize );
            Marshal.StructureToPtr( m_toolinfo, tempptr, false );

            SendMessage( m_wndToolTip, TTM_GETTOOLINFO, 0, tempptr );

            m_toolinfo = (TOOLINFO)Marshal.PtrToStructure( tempptr, typeof( TOOLINFO ) );

            act( m_toolinfo );

            Marshal.StructureToPtr( m_toolinfo, tempptr, false );

            SendMessage( m_wndToolTip, TTM_SETTOOLINFO, 0, tempptr );
        }
        finally
        {
            Marshal.FreeHGlobal( tempptr );
        }
    }

    readonly Control m_ownerControl;

    // The ToolTip's HWND
    IntPtr m_wndToolTip = IntPtr.Zero;

    /// 
The maximum width for a ToolTip window.
    /// If a ToolTip string exceeds the maximum width, the control breaks the text into multiple lines.
    int m_pxMaxWidth = 200;

    TOOLINFO m_toolinfo = new TOOLINFO();

    public BalloonToolTip( Control owner )
    {
        m_ownerControl = owner;

        // See http://msdn.microsoft.com/en-us/library/bb760252(VS.85).aspx#tooltip_sample_rect
        m_toolinfo.cbSize = Marshal.SizeOf( typeof( TOOLINFO ) );
        m_toolinfo.uFlags = TTF_TRANSPARENT | TTF_TRACK;
        m_toolinfo.hwnd = m_ownerControl.Handle;
        m_toolinfo.rect = m_ownerControl.Bounds;
    }

    /// 
Throws an exception if there's no alive WIN32 window.
    void VerifyControlIsAlive()
    {
        if( IntPtr.Zero == m_wndToolTip )
            throw new ApplicationException( "The control is not created, or is already destroyed." );
    }

    /// 
Create the balloon window.
    public void Create()
    {
        if( IntPtr.Zero != m_wndToolTip )
            Destroy();

        // Create the tooltip control.
        m_wndToolTip = CreateWindowEx( WS_EX_TOPMOST, "tooltips_class32",
            string.Empty,
            WS_POPUP | TTS_BALLOON | TTS_NOPREFIX | TTS_ALWAYSTIP,
            CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT,
            m_ownerControl.Handle, 0, 0, 0 );

        if( IntPtr.Zero == m_wndToolTip )
            throw new Win32Exception();

        if( !SetWindowPos( m_wndToolTip, HWND_TOPMOST,
                    0, 0, 0, 0,
                    SWP_NOMOVE | SWP_NOSIZE | SWP_NOACTIVATE ) )
            throw new Win32Exception();

        SetMaxTipWidth( m_wndToolTip, m_pxMaxWidth );
    }

    bool m_bVisible = false;

    /// 
return true if the balloon is currently visible.
    public bool bVisible
    {
        get
        {
            if( IntPtr.Zero == m_wndToolTip )
                return false;
            return m_bVisible;
        }
    }

    /// 
Balloon title.
    /// The balloon will only use the new value on the next Show() operation.
    public string strTitle;

    /// 
Balloon title icon.
    /// The balloon will only use the new value on the next Show() operation.
    public ToolTipIcon icon;

    /// 
Balloon title icon.
    /// The new value is updated immediately.
    public string strText
    {
        get { return m_toolinfo.text; }
        set
        {
            m_toolinfo.text = value;
            if( bVisible )
                UpdateTipText( m_wndToolTip, m_toolinfo );
        }
    }

    /// 
Show the balloon.
    /// The balloon stem position, in the owner's client coordinates.
    public void Show( Point pt )
    {
        VerifyControlIsAlive();

        if( m_bVisible ) Hide();

        // http://www.deez.info/sengelha/2008/06/12/balloon-tooltips/
        if( !AddTool( m_wndToolTip, m_toolinfo ) )
            throw new ApplicationException( "Unable to register the tooltip" );

        SetTitle( m_wndToolTip, icon, strTitle );

        TrackPosition( m_wndToolTip, m_ownerControl.PointToScreen( pt ) );

        TrackActivate( m_wndToolTip, true, m_toolinfo );

        m_bVisible = true;
    }

    /// 
Hide the balloon if it's visible.
    /// If the balloon was previously hidden, this method does nothing.
    public void Hide()
    {
        VerifyControlIsAlive();

        if( !m_bVisible ) return;

        TrackActivate( m_wndToolTip, false, m_toolinfo );

        DelTool( m_wndToolTip, m_toolinfo );

        m_bVisible = false;
    }

    /// 
Destroy the balloon.
    public void Destroy()
    {
        if( IntPtr.Zero == m_wndToolTip )
            return;
        if( m_bVisible ) Hide();

        DestroyWindow( m_wndToolTip );
        m_wndToolTip = IntPtr.Zero;
    }

    void IDisposable.Dispose()
    {
        Destroy();
    }
}

Here's my article with the complete source code.