xenadmin/XenAdmin/Controls/ComboBoxes/LongStringComboBox.cs

/* Copyright (c) Citrix Systems Inc. 
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 *     following disclaimer. 
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 *     copyright notice, this list of conditions and the 
 *     following disclaimer in the documentation and/or other 
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 * 
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 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF 
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using System;
using System.Drawing;
using System.Windows.Forms;

namespace XenAdmin.Controls
{
    /// <summary>
    /// A combobox that automatically resizes the dropdown's width to be as big
    /// as the longest string in the items list
    /// </summary>
    public class LongStringComboBox : ComboBox
    {
        private readonly ToolTip toolTip = new ToolTip();

        private bool disposed;
        protected override void Dispose(bool disposing)
        {
            if (disposing)
            {
                if (!disposed)
                {
                    toolTip.Dispose();
                }
                disposed = true;
            }
            base.Dispose(disposing);
        }

        protected override void OnDropDown(EventArgs e)
        {
            int totalWidth = MeasureLongestItem + VerticalScrollBarWidth;
            DropDownWidth = totalWidth > Width ? totalWidth : Width;
            base.OnDropDown(e);
        }

        protected override void OnCreateControl()
        {
            // Some strings can be very long, so we will show the value as a mouse over tooltip.
            // Initialize the tooltip here.
            toolTip.Active = true;
            toolTip.AutomaticDelay = 0;
            toolTip.AutoPopDelay = 50000;
            toolTip.InitialDelay = 50;
            toolTip.ReshowDelay = 50;
            toolTip.ShowAlways = true;

            base.OnCreateControl();
        }

        private int MeasureLongestItem
        {
            get
            {
                using (Graphics graphics = CreateGraphics())
                {
                    int longest = 0;
                    foreach (var item in Items)
                    {
                        int stringLength = (int) graphics.MeasureString(item.ToString(), Font).Width;
                        if (stringLength > longest)
                            longest = stringLength;
                    }
                    return longest;
                }
            }
        }

        private int MeasureTextWidth(string text)
        {
            using (Graphics graphics = CreateGraphics())
            {
                return (int) graphics.MeasureString(text, Font).Width;
            }
        }

        private int VerticalScrollBarWidth
        {
            get { return Items.Count > MaxDropDownItems ? SystemInformation.VerticalScrollBarWidth : 0; }
        }

        private const int DropDownButtonWidth = 10;

        protected override void OnSelectedIndexChanged(EventArgs e)
        {
            string itemText = SelectedItem != null ? SelectedItem.ToString() : string.Empty;
            int selectedItemTextWidth = !string.IsNullOrEmpty(itemText)
                                            ? MeasureTextWidth(itemText) + DropDownButtonWidth
                                            : 0;
            toolTip.SetToolTip(this, selectedItemTextWidth > ClientRectangle.Width ? itemText : string.Empty);

            base.OnSelectedIndexChanged(e);
        }
    }
}