OwnerDrawn ComboBox with Icons, Divider, and a generic data store

'Copyright (c) 2006 Patrick Sears
' No rights are conferred by this code, although you are allowed to use it freely.
' Just give credit where credit is due.
' 
' Remember, no warranty and no guarantee for any express purpose are given

Imports System.Windows.Forms
Imports System.IO
Imports System.Text
Imports System.ComponentModel
Imports System.Runtime.InteropServices
Imports System.Drawing

Public Class IconComboBox
    Inherits Windows.Forms.ComboBox

    Private m_CurrentItem As IconComboItem
    Private m_IconComboItemList As IconComboItemCollection

    ''' <summary>
    ''' Enumeration to indicate how the IconComboItemCollection gets changed
    ''' for various operations
    ''' </summary>
    ''' <remarks>Only used internally by IconComboBox</remarks>
    Public Enum IconComboItemCollectionChangeType
        ItemAdded = 0
        ItemRemoved
        ItemInserted
        CollectionCleared
    End Enum

    ''' <summary>
    ''' Get or set the tooltip text to be shown in the tooltip over the
    ''' combobox.
    ''' </summary>
    ''' <value>The new string to display in the tooltip.</value>
    ''' <returns>The string currently being displayed in the tooltip.</returns>
    ''' <remarks>This string defaults to the Data.ToString value when an item
    ''' in the ComboBox is selected.</remarks>
    Public Property ToolTipText() As String
        Get
            Return ToolTip1.GetToolTip(Me)
        End Get
        Set(ByVal value As String)
            ToolTip1.SetToolTip(Me, value)
        End Set
    End Property

    ''' <summary>
    ''' The collection of IconComboItems used to render the ComboBox.
    ''' </summary>
    ''' <returns>The collection of IconComboItems used to render the ComboBox.</returns>
    ''' <remarks>This property provides a similar interface to the .NET ComboBox, 
    ''' needing to call ComboBox1.Items.Add("MyStr") to add an item.</remarks>
    Public Overloads ReadOnly Property Items() As IconComboItemCollection
        Get
            Return m_IconComboItemList
        End Get
    End Property

    ''' <summary>
    ''' Gets the IconComboItem object for the currently selected item in the dropdown.
    ''' </summary>
    ''' <value></value>
    ''' <returns></returns>
    ''' <remarks></remarks>
    Public Overloads Property SelectedItem() As IconComboItem
        Get
            If Me.SelectedIndex >= 0 Then
                Return m_IconComboItemList(Me.SelectedIndex)
            Else
                Return Nothing
            End If
        End Get
        Set(ByVal Value As IconComboItem)
            m_CurrentItem = Value
        End Set
    End Property

    ''' <summary>
    ''' Creates a new instance of the IconComboBox.
    ''' </summary>
    ''' <remarks></remarks>
    Public Sub New()
        MyBase.New()

        InitializeComponent()

        m_IconComboItemList = New IconComboItemCollection
        AddHandler m_IconComboItemList.CollectionChanged, AddressOf m_IconComboItemList_CollectionItemsChanged
        'Set to OwnerDraw
        Me.DrawMode = Windows.Forms.DrawMode.OwnerDrawFixed
        'Must be set to DropDownList
        Me.DropDownStyle = ComboBoxStyle.DropDownList
    End Sub

    'ComboBox must have its style set to DropDownList
    Private Sub ExpCombo_DropDownStyleChanged(ByVal sender As Object, ByVal e As System.EventArgs)
        Me.DropDownStyle = ComboBoxStyle.DropDownList
    End Sub

    'Make sure font doesn't get set to more than 12 points
    Protected Overrides Sub OnFontChanged(ByVal e As System.EventArgs)
        If Me.Font.SizeInPoints > 12 Then
            Me.Font = New Font(Me.Font.FontFamily, 12, Me.Font.Style)
        End If
    End Sub

    Protected Overrides Sub OnSelectedIndexChanged(ByVal e As System.EventArgs)
        If Me.SelectedIndex < 0 Then
            Exit Sub
        End If

        If Me.SelectedIndex < m_IconComboItemList.Count Then
            If m_IconComboItemList(Me.SelectedIndex).IsDivider Then
                If Me.SelectedIndex > 0 Then
                    Me.SelectedIndex -= 1
                    m_CurrentItem = m_IconComboItemList(Me.SelectedIndex)
                ElseIf Me.SelectedIndex < m_IconComboItemList.Count - 1 Then
                    Me.SelectedIndex += 1
                    m_CurrentItem = m_IconComboItemList(Me.SelectedIndex)
                End If
            Else
                m_CurrentItem = m_IconComboItemList(Me.SelectedIndex)
                MyBase.OnSelectedIndexChanged(e)
            End If

            ' Set the default ToolTip string.
            ToolTip1.SetToolTip(Me, m_CurrentItem.Data)
        End If
    End Sub

    ''' <summary>
    ''' Draws an IconComboBox item into the ComboBox in the area specified by the DrawItemEventArgs.
    ''' </summary>
    ''' <param name="e">Event argument specifying which item to draw and where to draw it.</param>
    ''' <remarks></remarks>
    Protected Overrides Sub OnDrawItem(ByVal e As System.Windows.Forms.DrawItemEventArgs)
        e.DrawBackground()
        e.DrawFocusRectangle()

        Dim bounds As Rectangle = e.Bounds
        If e.Index > -1 AndAlso e.Index < Me.Items.Count AndAlso e.Index < m_IconComboItemList.Count Then
            Dim currentItem As IconComboItem = m_IconComboItemList(e.Index)

            If currentItem IsNot Nothing Then
                If currentItem.IsDivider Then
                    Dim xStart As Single = bounds.X + 10
                    Dim yStart As Single = Convert.ToSingle(bounds.Y + bounds.Height / 2 + 1)
                    Dim xEnd As Single = bounds.Width - 10
                    Dim yEnd As Single = yStart
                    e.Graphics.DrawLine(Pens.Black, xStart, yStart, xEnd, yEnd)

                    yStart = Convert.ToSingle(bounds.Y + bounds.Height / 2 - 1)
                    yEnd = yStart
                    e.Graphics.DrawLine(Pens.Black, xStart, yStart, xEnd, yEnd)
                Else
                    Dim imageSize As Size
                    Dim fileNameOnly As String = currentItem.DisplayText 'Items(e.Index).ToString()
                    Dim fullFileName As String = currentItem.Data
                    Dim fileIcon As Icon = currentItem.ItemImage
                    Dim imageRectangle As New Rectangle(bounds.Left + 1, bounds.Top + 1, ItemHeight, ItemHeight)

                    If fileIcon IsNot Nothing Then
                        e.Graphics.DrawIcon(fileIcon, imageRectangle)
                    End If
                    imageSize = imageRectangle.Size

                    Dim fileNameRec As New Rectangle(bounds.Left + imageSize.Width + 3, bounds.Top, bounds.Width - imageSize.Width - 3, bounds.Height)
                    Dim format As New StringFormat()
                    format.LineAlignment = StringAlignment.Center
                    e.Graphics.DrawString(fileNameOnly, e.Font, New SolidBrush(e.ForeColor), fileNameRec, format)
                End If
            Else
                Console.WriteLine("Error, the selected item is nothing")
            End If
        End If

        MyBase.OnDrawItem(e)
    End Sub

    ''' <summary>
    ''' Add a divider line to the ComboBox.  The line will be appended to the end of the list.
    ''' </summary>
    ''' <returns>The index of the added divider.</returns>
    ''' <remarks></remarks>
    Public Function AddDivider() As Integer
        Dim tempItem As New IconComboItem
        'tempItem.ItemImage = Nothing
        'tempItem.Data = Nothing
        tempItem.DisplayText = ""
        tempItem.IsDivider = True

        Return Me.Items.Add(tempItem)
    End Function

    ' I am forced to raise an event from the IconComboItemCollection to inform me when it changes - 
    ' e.g. the user calls Items.Clear, Items.Add, or Items.Remove.  I need to be notified of this so that
    ' I can remove the corresponding item from the base ComboBox object collection.
    Private Sub m_IconComboItemList_CollectionItemsChanged(ByVal sender As Object, ByVal e As IconComboItemCollectionChangedEventArgs)
        If e.ChangeType = IconComboItemCollectionChangeType.ItemAdded Then
            MyBase.Items.Add(e.ChangedItem.DisplayText)
        ElseIf e.ChangeType = IconComboItemCollectionChangeType.ItemInserted Then
            MyBase.Items.Insert(e.ChangedIndex, e.ChangedItem.DisplayText)
        ElseIf e.ChangeType = IconComboItemCollectionChangeType.ItemRemoved Then
            MyBase.Items.Remove(e.ChangedItem.DisplayText)
        ElseIf e.ChangeType = IconComboItemCollectionChangeType.CollectionCleared Then
            MyBase.Items.Clear()
        End If
    End Sub

#Region "Class IconComboItem"
    ''' <summary>
    ''' Object representing an entry in the IconComboBox.
    ''' </summary>
    ''' <remarks>Implements IEquatable for searching and sorting the IconComboItemCollection.</remarks>
    Public Class IconComboItem
        Implements IEquatable(Of IconComboItem)

        Private m_Icon As Icon
        Private m_Data As String
        Private m_DisplayText As String
        Private m_isDivider As Boolean

        ''' <summary>
        ''' The image to be displayed next to the text for this combo box item.
        ''' </summary>
        ''' <value>The icon to be displayed</value>
        ''' <returns>The icon currently being displayed</returns>
        ''' <remarks></remarks>
        Public Property ItemImage() As Icon
            Get
                Return m_Icon
            End Get
            Set(ByVal value As Icon)
                m_Icon = value
            End Set
        End Property

        ''' <summary>
        ''' The string representing data you want associated with this IconComboItem.
        ''' </summary>
        ''' <value>The data to be set</value>
        ''' <returns>The data currently saved</returns>
        ''' <remarks></remarks>
        Public Property Data() As String
            Get
                Return m_Data
            End Get
            Set(ByVal value As String)
                m_Data = value
            End Set
        End Property

        ''' <summary>
        ''' What to display for this item.
        ''' </summary>
        ''' <value></value>
        ''' <returns></returns>
        ''' <remarks></remarks>
        Public Property DisplayText() As String
            Get
                Return m_DisplayText
            End Get
            Set(ByVal value As String)
                m_DisplayText = value
            End Set
        End Property

        ''' <summary>
        ''' Indicates whether this IconComboItem is a divider.
        ''' </summary>
        ''' <value>Boolean indicating if this item is a divider or not.  This property can only be SET
        ''' by the IconComboBox.</value>
        ''' <returns>True if this is a divider; False if it is not.</returns>
        ''' <remarks></remarks>
        Public Property IsDivider() As Boolean
            Get
                Return m_isDivider
            End Get
            ' This property is Friend so that ONLY THE IconComboBox can set this property.
            Friend Set(ByVal value As Boolean)
                m_isDivider = value
            End Set
        End Property

        Public Sub New()
        End Sub

        ''' <summary>
        ''' Create a new IconComboItem with the specified values
        ''' </summary>
        ''' <param name="argText">The text to display in the combo box</param>
        ''' <param name="argData">The string representing this IconComboItem's data</param>
        ''' <remarks></remarks>
        Public Sub New(ByVal argText As String, ByVal argData As String)
            m_DisplayText = argText
            m_Data = argData
        End Sub

        Public Shared Operator =(ByVal item1 As IconComboItem, ByVal item2 As IconComboItem) As Boolean
            Return item1.Data = item2.Data
        End Operator

        Public Shared Operator <>(ByVal item1 As IconComboItem, ByVal item2 As IconComboItem) As Boolean
            Return item1.Data <> item2.Data
        End Operator

        ''' <summary>
        ''' Returns if this IconComboItem is equal to the specified one.
        ''' </summary>
        ''' <param name="other">The IconComboItem to compare</param>
        ''' <returns>True if this item's Data property equals the other item's Data property.</returns>
        ''' <remarks></remarks>
        Public Overloads Function Equals(ByVal other As IconComboItem) As Boolean Implements System.IEquatable(Of IconComboItem).Equals
            Return m_Data = other.Data
        End Function
    End Class
#End Region

#Region "Class IconComboItemCollection"
    Public Class IconComboItemCollection

        Private m_List As New Generic.List(Of IconComboBox.IconComboItem)
        Friend Event CollectionChanged(ByVal sender As Object, ByVal e As IconComboItemCollectionChangedEventArgs)

        ''' <summary>
        ''' The number of items in the current collection
        ''' </summary>
        ''' <value></value>
        ''' <returns></returns>
        ''' <remarks></remarks>
        Public ReadOnly Property Count() As Integer
            Get
                Return m_List.Count
            End Get
        End Property

        ''' <summary>
        ''' Gets the IconComboItem at the specfied index
        ''' </summary>
        ''' <param name="index">The index of the IconComboItem to return</param>
        ''' <value></value>
        ''' <returns>The IconComboItem at the specified index, or nothing if the index is out of range.</returns>
        ''' <remarks></remarks>
        Default Public ReadOnly Property Item(ByVal index As Integer) As IconComboItem
            Get
                If index < m_List.Count Then
                    Return m_List(index)
                Else
                    Return Nothing
                End If
            End Get
        End Property

        ''' <summary>
        ''' Add the specified IconComboItem to the end of the collection.
        ''' </summary>
        ''' <param name="argItem">The IconComboItem to add.  Can be Null.</param>
        ''' <returns>The zero-based index where the IconComboItem was added.</returns>
        ''' <remarks></remarks>
        Public Function Add(ByVal argItem As IconComboItem) As Integer
            m_List.Add(argItem)
            RaiseEvent CollectionChanged(Me, New IconComboItemCollectionChangedEventArgs(m_List.Count - 1, IconComboBox.IconComboItemCollectionChangeType.ItemAdded, argItem))
            Return m_List.Count - 1
        End Function

        ''' <summary>
        ''' Insert the specified IconComboItem at the specified index.
        ''' </summary>
        ''' <param name="idx"></param>
        ''' <param name="argItem"></param>
        ''' <returns></returns>
        ''' <remarks></remarks>
        Public Function Insert(ByVal idx As Integer, ByVal argItem As IconComboItem) As Boolean
            m_List.Insert(idx, argItem)

            If m_List(idx) = argItem Then
                RaiseEvent CollectionChanged(Me, New IconComboItemCollectionChangedEventArgs(idx, IconComboBox.IconComboItemCollectionChangeType.ItemInserted, argItem))
                Return True
            End If
            Return False
        End Function

        Public Function Remove(ByVal argItem As IconComboItem) As Boolean
            If m_List.Remove(argItem) Then
                RaiseEvent CollectionChanged(Me, New IconComboItemCollectionChangedEventArgs(0, IconComboBox.IconComboItemCollectionChangeType.ItemRemoved, argItem))
                Return True
            End If
            Return False
        End Function

        ''' <summary>
        ''' Clear all the items from this collection and from the combo box.
        ''' </summary>
        ''' <remarks></remarks>
        Public Sub Clear()
            m_List.Clear()
            RaiseEvent CollectionChanged(Me, New IconComboItemCollectionChangedEventArgs(-1, IconComboItemCollectionChangeType.CollectionCleared, Nothing))
        End Sub

        ''' <summary>
        ''' Determine if the collection contains the specified IconComboItem, using the 
        ''' <see>IconComboItem.Equals</see> method for comparison.
        ''' </summary>
        ''' <param name="item"></param>
        ''' <returns></returns>
        ''' <remarks></remarks>
        Public Function Contains(ByVal item As IconComboItem) As Boolean
            'For Each tempitem As IconComboItem In List
            '    If tempitem.Equals(item) Then
            '        Return True
            '    End If
            'Next
            'Return False
            'Return List.Contains(item)
            Return m_List.Contains(item)
        End Function

        ''' <summary>
        ''' Searches for the specified IconComboItem and returns the zero-based index of the first 
        ''' occurrence within the entire IconComboItemCollection.
        ''' </summary>
        ''' <param name="item">The object to locate in the IconComboItemCollection. 
        ''' The value can be null for reference types.</param>
        ''' <returns>The zero-based index of the first occurrence of item within 
        ''' the entire IconComboItemCollection, if found; otherwise, �1.</returns>
        ''' <remarks></remarks>
        Public Function IndexOf(ByVal item As IconComboItem) As Integer
            Return m_List.IndexOf(item)
        End Function
    End Class
#End Region

#Region "Friend Class IconComboItemCollectionChangedEventArgs"
    ''' <summary>
    ''' These args are used in events indicating that the IconComboItemCollection has been
    ''' changed.  This class can only be used by the IconComboBox.
    ''' </summary>
    ''' <remarks></remarks>
    Friend Class IconComboItemCollectionChangedEventArgs
        Inherits EventArgs

        Private m_ChangeType As IconComboBox.IconComboItemCollectionChangeType
        Private m_ChangedItem As IconComboBox.IconComboItem
        Private m_ChangedIndex As Integer

        ''' <summary>
        ''' Indicates how the IconComboItemCollection was changed - add, delete, remove, or clear.
        ''' </summary>
        ''' <value></value>
        ''' <returns></returns>
        ''' <remarks></remarks>
        Public ReadOnly Property ChangeType() As IconComboBox.IconComboItemCollectionChangeType
            Get
                Return m_ChangeType
            End Get
        End Property

        ''' <summary>
        ''' The item that was changed resulting in this event.
        ''' </summary>
        ''' <value></value>
        ''' <returns></returns>
        ''' <remarks></remarks>
        Public ReadOnly Property ChangedItem() As IconComboBox.IconComboItem
            Get
                Return m_ChangedItem
            End Get
        End Property

        ''' <summary>
        ''' The index of the changed item in the IconComboItemCollection.
        ''' </summary>
        ''' <value></value>
        ''' <returns></returns>
        ''' <remarks></remarks>
        Public ReadOnly Property ChangedIndex() As Integer
            Get
                Return m_ChangedIndex
            End Get
        End Property

        ''' <summary>
        ''' Create a new instance of these event args with the specified arguments
        ''' </summary>
        ''' <param name="argidx">Index of the changed item</param>
        ''' <param name="argType">How the item was changed. <seealso>IconComboBox.IconComboItemCollectionChangeType</seealso></param>
        ''' <param name="argItem">The <see>IconComboItem</see> that was changed</param>
        ''' <remarks></remarks>
        Public Sub New(ByVal argidx As Integer, ByVal argType As IconComboBox.IconComboItemCollectionChangeType, ByVal argItem As IconComboBox.IconComboItem)
            m_ChangeType = argType
            m_ChangedItem = argItem
            m_ChangedIndex = argidx
        End Sub
    End Class
#End Region
End Class