/Windows/ThreeStateTreeNode.cs

using System;

using System.ComponentModel;

using System.Text;

using System.Windows.Forms;



namespace JoshuaOneEight.Windows

{

    /// <summary>

    /// ThreeStateTreeNode inherits from <see cref="http://msdn2.microsoft.com/en-us/library/system.windows.forms.treenode.aspx">TreeNode</see>

    /// and adds the ability to support a third, indeterminate state as well as optionally cascading state changes to related nodes, i.e.

    /// child nodes and or parent nodes, as determined by this instance's related parent TreeView settings, CascadeNodeChecksToChildNodes and

    /// CascadeNodeChecksToParentNode.

    /// </summary>

    public class ThreeStateTreeNode : TreeNode

    {

        #region Constructors

        /// <summary>

        /// Initializes a new instance of the ThreeStateTreeNode class in addition to intializing

        /// the base class (<see cref="http://msdn2.microsoft.com/en-us/library/bk8h64c9.aspx">TreeNode Constructor</see>). 

        /// </summary>

        public ThreeStateTreeNode() : base()

        {

            this.CommonConstructor();

        }

        

        /// <summary>

        /// Initializes a new instance of the ThreeStateTreeNode class with a string for the text label to display in addition to intializing

        /// the base class (<see cref="http://msdn2.microsoft.com/en-us/library/ytx906df.aspx">TreeNode Constructor</see>). 

        /// </summary>

        /// <param name="text">The string for the label of the new tree node.</param>

        public ThreeStateTreeNode(string text) : base(text)

        {

            this.CommonConstructor();

        }



        /// <summary>

        /// Initializes a new instance of the ThreeStateTreeNode class with a string for the text label to display 

        /// and an array of child ThreeStateTreeNodes in addition to intializing the base class 

        /// (<see cref="http://msdn2.microsoft.com/en-us/library/774ty506.aspx">TreeNode Constructor</see>). 

        /// </summary>

        /// <param name="text">The string for the label of the new tree node.</param>

        /// <param name="children">An array of child ThreeStateTreeNodes.</param>

        public ThreeStateTreeNode(string text, ThreeStateTreeNode[] children) : base(text, children)

        {

            this.CommonConstructor();

        }

        

        /// <summary>

        /// Initializes a new instance of the ThreeStateTreeNode class with a string for the text label to display 

        /// and the selected and unselected image indexes in addition to intializing the base class 

        /// (<see cref="http://msdn2.microsoft.com/en-us/library/8dfy3k5t.aspx">TreeNode Constructor</see>). 

        /// </summary>

        /// <param name="text">The string for the label of the new tree node.</param>

        /// <param name="imageIndex">The image index of the unselected image in the parent TreeView's <see cref="http://msdn2.microsoft.com/en-us/library/system.windows.forms.treeview.imagelist.aspx">ImageList</see>.</param>

        /// <param name="selectedImageIndex">The image index of the selected image in the parent TreeView's <see cref="http://msdn2.microsoft.com/en-us/library/system.windows.forms.treeview.imagelist.aspx">ImageList</see>.</param>

        public ThreeStateTreeNode(string text, int imageIndex, int selectedImageIndex) : base(text, imageIndex, selectedImageIndex)

        {

            this.CommonConstructor(); 

        }



        /// <summary>

        /// Initializes a new instance of the ThreeStateTreeNode class with a string for the text label to display ,

        /// the selected and unselected image indexes, and an array of child ThreeStateTreeNodes in addition to intializing the base class 

        /// (<see cref="http://msdn2.microsoft.com/en-us/library/8dfy3k5t.aspx">TreeNode Constructor</see>). 

        /// </summary>

        /// <param name="text">The string for the label of the new tree node.</param>

        /// <param name="imageIndex">The image index of the unselected image in the parent TreeView's <see cref="http://msdn2.microsoft.com/en-us/library/system.windows.forms.treeview.imagelist.aspx">ImageList</see>.</param>

        /// <param name="selectedImageIndex">The image index of the selected image in the parent TreeView's <see cref="http://msdn2.microsoft.com/en-us/library/system.windows.forms.treeview.imagelist.aspx">ImageList</see>.</param>

        /// <param name="children">An array of child ThreeStateTreeNodes.</param>

        public ThreeStateTreeNode(string text, int imageIndex, int selectedImageIndex, ThreeStateTreeNode[] children) : base(text, imageIndex, selectedImageIndex, children) 

        {

            this.CommonConstructor(); 

        }

        #endregion



        #region Initialization

        /// <summary>

        /// Performs common initialization to all constructors.

        /// </summary>

        private void CommonConstructor()

        {

        }

        #endregion



        #region Properties

        /// <summary>

        /// The current state of the checkbox.

        /// </summary>

        private CheckBoxState mState = CheckBoxState.Unchecked;

        [Category("Three State TreeView"), 

        Description("The current state of the node's checkbox, Unchecked, Checked, or Indeterminate"),

        DefaultValue(CheckBoxState.Unchecked),

        TypeConverter(typeof(CheckBoxState)),

		Editor( "JoshuaOneEight.CheckBoxState", typeof( CheckBoxState ) )]

        public CheckBoxState State

        {

            get { return this.mState; }

            set 

            {

                if (this.mState != value)

                {

                    this.mState = value;



					switch( value )

					{

						case CheckBoxState.Unchecked:

							this.ImageIndex = 0;

							this.SelectedImageIndex = 0;

							break;

						case CheckBoxState.Checked:

							this.ImageIndex = 1;

							this.SelectedImageIndex = 1;

							break;

						default:

							this.ImageIndex = 2;

							this.SelectedImageIndex = 2;

							break;

					}

                }

            }

        }



        /// <summary>

        /// Returns the 'combined' state for all siblings of a node.

        /// </summary>

        private CheckBoxState SiblingsState

        {

            get

            {

                // If parent is null, cannot have any siblings or if the parent

                // has only one child (i.e. this node) then return the state of this 

                // instance as the state.

                if ((this.Parent == null) || (this.Parent.Nodes.Count == 1))

                    return this.State;



                // The parent has more than one child.  Walk through parent's child

                // nodes to determine the state of all this node's siblings,

                // including this node.

                CheckBoxState state = 0;

                foreach (TreeNode node in this.Parent.Nodes)

                {

                    ThreeStateTreeNode child = node as ThreeStateTreeNode;

                    if (child != null)

                        state |= child.State;



                    // If the state is now indeterminate then know there

                    // is a combination of checked and unchecked nodes

                    // and no longer need to continue evaluating the rest

                    // of the sibling nodes.

                    if (state == CheckBoxState.Indeterminate)

                        break;

                }



                return (state == 0) ? CheckBoxState.Unchecked : state;

            }

        }

        #endregion



        #region Methods

        /// <summary>

        /// Manages state changes from one state to the next.

        /// </summary>

        /// <param name="fromState">The state upon which to base the state change.</param>

        public void Toggle(CheckBoxState fromState)

        {

            switch (fromState)

            {

                case CheckBoxState.Unchecked:

                    {

                        this.State = CheckBoxState.Checked;

                        break;

                    }

                case CheckBoxState.Checked:

                case CheckBoxState.Indeterminate:

                default:

                    {

                        this.State = CheckBoxState.Unchecked;

                        break;

                    }

            }



            this.UpdateStateOfRelatedNodes();

        }



        /// <summary>

        /// Manages state changes from one state to the next.

        /// </summary>

        public new void Toggle()

        {

            this.Toggle(this.State);

        }



        /// <summary>

        /// Manages updating related child and parent nodes of this instance.

        /// </summary>

        public void UpdateStateOfRelatedNodes()

        {

            ThreeStateTreeView tv = this.TreeView as ThreeStateTreeView;

            if ((tv != null) && tv.UseThreeStateCheckBoxes)

            {

                tv.BeginUpdate();



                // If want to cascade checkbox state changes to child nodes of this node and

                // if the current state is not intermediate, update the state of child nodes.

                if (this.State != CheckBoxState.Indeterminate)

                    this.UpdateChildNodeState();



                this.UpdateParentNodeState(true);



                tv.EndUpdate();

            }

        }



        /// <summary>

        /// Recursiveley update child node's state based on the state of this node.

        /// </summary>

        private void UpdateChildNodeState()

        {

            ThreeStateTreeNode child;

            foreach (TreeNode node in this.Nodes)

            {

                // It is possible node is not a ThreeStateTreeNode, so check first.

                if (node is ThreeStateTreeNode)

                {

                    child = node as ThreeStateTreeNode;

                    child.State = this.State;

                    child.Checked = (this.State != CheckBoxState.Unchecked);

                    child.UpdateChildNodeState();

                }

            }

        }



        /// <summary>

        /// Recursiveley update parent node state based on the current state of this node.

        /// </summary>

        private void UpdateParentNodeState(bool isStartingPoint)

        {

            // If isStartingPoint is false, then know this is not the initial call

            // to the recursive method as we want to force on the first time

            // this is called to set the instance's parent node state based on

            // the state of all the siblings of this node, including the state

            // of this node.  So, if not the startpoint (!isStartingPoint) and

            // the state of this instance is indeterminate (Enumerations.CheckBoxState.Indeterminate)

            // then know to set all subsequent parents to the indeterminate

            // state.  However, if not in an indeterminate state, then still need

            // to evaluate the state of all the siblings of this node, including the state

            // of this node before setting the state of the parent of this instance.



            ThreeStateTreeNode parent = this.Parent as ThreeStateTreeNode;

            if (parent != null)

            {

                CheckBoxState state = CheckBoxState.Unchecked;

                

                // Determine the new state

                if (!isStartingPoint && (this.State == CheckBoxState.Indeterminate))

                    state = CheckBoxState.Indeterminate;

                else

                    state = this.SiblingsState;



                // Update parent state if not the same.

                if (parent.State != state)

                {

                    parent.State = state;

                    parent.Checked = (state != CheckBoxState.Unchecked);

                    parent.UpdateParentNodeState(false);

                }

            }

        }

        #endregion

    }

}