3rdpartylibs/fastreports.wpf/FastReport.DesignExt/Controls/ToolTipListBox.cs

// written by Mehul Dhorda https://www.codeproject.com/Articles/457444/Listbox-Control-with-Tooltip-for-Each-Item
// licensed under CPOL 

using System;
using System.Windows.Forms;

namespace FastReport.Controls
{
    internal class ListBoxItem : IToolTipDisplayer
    {
        public string DisplayText { get; }
        public string ToolTipText { get; }

        public ListBoxItem(string displayText, string toolTipText)
        {
            DisplayText = displayText;
            ToolTipText = toolTipText;
        }

        public override string ToString() => DisplayText;

        public string GetToolTipText() => ToolTipText;
    }

    internal interface IToolTipDisplayer
    {
        string GetToolTipText();
    }

    internal class ToolTipListBox : ListBox
    {
        // The item index that the mouse is currently over
        private int _currentItem;

        // A value indicating if the current item has been set
        private bool _currentItemSet;

        // A value indicating if a tooltip is currently being displayed
        private bool _toolTipDisplayed;

        // Timer that is used to wait for the mouse to hover over an item
        private Timer _toolTipDisplayTimer;

        // Tooltip control
        private ToolTip _toolTip;

        protected override void OnMouseMove(MouseEventArgs e)
        {
            base.OnMouseMove(e);
            int itemIndex = this.IndexFromPoint(e.Location);

            if (itemIndex == ListBox.NoMatches)
            {
                // Mouse is over empty space in the listbox so hide tooltip
                _toolTip.Hide(this);
                _currentItemSet = false;
                _toolTipDisplayed = false;
                _toolTipDisplayTimer.Stop();
            }
            else if (!_currentItemSet)
            {
                // Mouse is over a new item so start timer to display tooltip
                _currentItem = itemIndex;
                _currentItemSet = true;
                _toolTipDisplayTimer.Start();
            }
            else if (itemIndex != _currentItem)
            {
                // Mouse is over a different item so hide tooltip and restart timer
                _currentItem = itemIndex;
                _toolTipDisplayTimer.Stop();
                _toolTipDisplayTimer.Start();
                _toolTip.Hide(this);
                _toolTipDisplayed = false;
            }
        }

        protected override void OnMouseLeave(EventArgs e)
        {
            base.OnMouseLeave(e);
            // Mouse has left listbox so stop timer (tooltip is automatically hidden)
            _currentItemSet = false;
            _toolTipDisplayed = false;
            _toolTipDisplayTimer.Stop();
        }

        private void _toolTipDisplayTimer_Tick(object sender, EventArgs e)
        {
            // Display tooltip text since the mouse has hovered over an item
            if (!_toolTipDisplayed && _currentItem != ListBox.NoMatches &&
                        _currentItem < this.Items.Count)
            {
                IToolTipDisplayer toolTipDisplayer = this.Items[_currentItem] as IToolTipDisplayer;
                if (toolTipDisplayer != null)
                {
                    _toolTip.SetToolTip(this, toolTipDisplayer.GetToolTipText());
                    _toolTipDisplayed = true;
                }
            }
        }

        public ToolTipListBox()
        {
            _currentItemSet = false;
            _toolTipDisplayed = false;
            _toolTipDisplayTimer = new Timer();
            _toolTip = new ToolTip();

            // Set the timer interval to the system time that it takes for a tooltip to appear
            _toolTipDisplayTimer.Interval = SystemInformation.MouseHoverTime;
            _toolTipDisplayTimer.Tick += _toolTipDisplayTimer_Tick;
        }
    }
}