To reproduce:
Add a RadGanttView, add a single column and subscribe to the TextViewCellFormatting event. You will notice that the event is not being fired.

Open QSF, go to GanttView, open the First Look demo, click a date time cell in, click anywhere else, exception occurs.

Description: Show context menu in RadGanttView (to enable adding, deleting tasks and setting progress) not only for the GraphicalViewElement, but also for the TextViewElement

Add functionality of GraphicalViewElement for ScrollTo(DateTime dt)

To reproduce have a button with this handler: 
 private void rbtnRemoveTasks_Click(object sender, EventArgs e)
        {
            if (ganttView.SelectedItem != null)
            {
                if (ganttView.SelectedItem.Parent != null)
              

When scrolling, the gantt final date for several tasks increases without any reason. If afterwards I select any task the incorrect final dates are corrected. But if I once again start to scroll, the problem shows up again.

Add a gantt populated with some data.

Increase column sizes in the text part on a way that an editor is outside the view

Scroll to the editor and open it for edit

Scroll back on a way that the editor is no longer into view => exception is thrown

Workaround: 
        radGanttView1.GanttViewElement.TextViewElement.ColumnScroller.Scrollbar.ValueChanged+=Scrollbar_ValueChanged;

        void Scrollbar_ValueChanged(object sender, EventArgs e)
        {
            radGanttView1.GanttViewElement.EndEdit();
        }

To reproduce:

Bind to an object with a property of type double. Start the application and edit that same column. End the editing process and you will see an exception that decimal cannot be converted to double.

Workaround:

Create the following custom editor:

public class MySpinEditor : GanttViewSpinEditor
{
    public override object Value
    {
        get
        {
            object value = base.Value;
            return Convert.ChangeType(value, this.ValueType);
        }
        set
        {
            base.Value = value;
        }
    }
}

Subscribe to the EditorInitialized and EditorRequired events and use the following event handlers:

void GanttViewElement_EditorInitialized(object sender, GanttViewItemEditorInitializedEventArgs e)
{
    GanttViewSpinEditor spinEditor = e.Editor as GanttViewSpinEditor;
    if (spinEditor != null)
    {
        spinEditor.ValueType = typeof(double);
    }
}


void GanttViewElement_EditorRequired(object sender, GanttViewEditorRequiredEventArgs e)
{
    if (e.EditorType == typeof(GanttViewSpinEditor))
    {
        e.EditorType = typeof(MySpinEditor);
    }
}

To reproduce:

Add a RadGanttView to a form and set its Dock to Fill. Increase the size of the form. Add 3-4 events to the RadGanttView and start the application. Reduce the size of the form until the gantt is small enough so scrollbars should show. You will notice that the vertical scrollbars will not show.

Steps to reproduce:

1. Add a gantt view to a form and add two buttons, one for adding a new child to the selected item and one for removing the selected item.
2. Run the project and add child items to a normal task item - the item should become a summary item.
3. Remove all the child items of a summary item - it should become a normal task.

Improve the way to format easily summary task. Currently you need to cast all elements of summary element to change the BackColor. 

Resolution: 
There are three properties added to GanttViewSummaryElement which allow access to the inner elements: LeftElement, MiddleElement and RightElement. 
Please take a look at the code example: 
private void radGanttView1_GraphicalViewItemFormatting(object sender, GanttViewGraphicalViewItemFormattingEventArgs e)
{
    GanttViewSummaryItemElement element = e.ItemElement as GanttViewSummaryItemElement;
    if (element != null)
    {
        GanttViewSummaryElement summary = element.TaskElement as GanttViewSummaryElement;
        summary.LeftElement.BackColor = Color.Blue;
        summary.RightElement.BackColor = Color.Blue;
        summary.MiddleElement.BackColor = Color.LightGreen;
        summary.ProgressIndicatorElement.BackColor = Color.Red;
    }
}

Currently users are not able to create custom item elements for the gantt view timeline. 

Steps to reproduce:

1. Add six items to a RadGanttView

2. Start reducing the height of the gantt view

You will notice that the vertical scroll bar does not appear until two of the items are hidden. Before that the hidden items cannot be scrolled to.

1. Set up a RadGanttView with some data

2. Do not add any columns

3. Run the project and press the Left or Right Arrow key. An IndexOutOfRange exception will be thrown.

To reproduce: use the following code snippet and perform the described steps below:

Sub New()
    InitializeComponent()

    PopulateData()
End Sub

Private Sub PopulateData()

    Dim tasks As New DataTable("Tasks")
    tasks.Columns.Add("Id", GetType(Integer))
    tasks.Columns.Add("ParentId", GetType(Integer))
    tasks.Columns.Add("Title", GetType(String))
    tasks.Columns.Add("Start", GetType(DateTime))
    tasks.Columns.Add("End", GetType(DateTime))
    tasks.Columns.Add("Progress", GetType(Decimal))

    Dim links As New DataTable("Links")
    links.Columns.Add("StartId", GetType(Integer))
    links.Columns.Add("EndId", GetType(Integer))
    links.Columns.Add("LinkType", GetType(Integer))

    Dim data As New DataSet()
    data.Tables.Add(tasks)
    data.Tables.Add(links)

    tasks.Rows.Add(1, 0, "Summary task title", New DateTime(2010, 10, 10), New DateTime(2010, 10, 15), 30D)
    tasks.Rows.Add(2, 1, "First child task title", New DateTime(2010, 10, 10), New DateTime(2010, 10, 12), 10)
    tasks.Rows.Add(3, 1, "Second child task title", New DateTime(2010, 10, 12), New DateTime(2010, 10, 15), 20D)
    tasks.Rows.Add(4, 1, "Milestone", New DateTime(2010, 10, 15), New DateTime(2010, 10, 15), 0D)

    links.Rows.Add(2, 3, 1)
    links.Rows.Add(3, 4, 1)

    Me.RadGanttView1.GanttViewElement.TaskDataMember = "Tasks"
    Me.RadGanttView1.GanttViewElement.ChildMember = "Id"
    Me.RadGanttView1.GanttViewElement.ParentMember = "ParentId"
    Me.RadGanttView1.GanttViewElement.TitleMember = "Title"
    Me.RadGanttView1.GanttViewElement.StartMember = "Start"
    Me.RadGanttView1.GanttViewElement.EndMember = "End"
    Me.RadGanttView1.GanttViewElement.ProgressMember = "Progress"
    Me.RadGanttView1.GanttViewElement.LinkDataMember = "Links"
    Me.RadGanttView1.GanttViewElement.LinkStartMember = "StartId"
    Me.RadGanttView1.GanttViewElement.LinkEndMember = "EndId"
    Me.RadGanttView1.GanttViewElement.LinkTypeMember = "LinkType"

    Me.RadGanttView1.GanttViewElement.DataSource = data

    Me.RadGanttView1.Columns.Clear()
    Me.RadGanttView1.Columns.Add("Start")
    Me.RadGanttView1.Columns.Add("End")
    Me.RadGanttView1.GanttViewElement.GraphicalViewElement.TimelineStart = New DateTime(2010, 10, 9)
    Me.RadGanttView1.GanttViewElement.GraphicalViewElement.TimelineEnd = New DateTime(2010, 12, 10)
End Sub

Private Sub RadButton1_Click(sender As Object, e As EventArgs) Handles RadButton1.Click
    Dim selected = Me.RadGanttView1.SelectedItem.Title

    Me.RadGanttView1.DataSource = Nothing
    PopulateData()

    Dim result = FindDataItem(selected, Me.RadGanttView1.Items)

    If result IsNot Nothing Then
        Me.RadGanttView1.SelectedItem = result
    End If
End Sub

Dim found = Nothing
Private Function FindDataItem(selected As String, items As GanttViewDataItemCollection) As GanttViewDataItem

    For Each item As GanttViewDataItem In items
        If item.Title = selected Then
            Return item
        End If

        Dim itm As GanttViewDataItem = FindDataItem(selected, item.Items)

        If itm IsNot Nothing Then
            Return itm
        End If
    Next
    Return Nothing
End Function

1.Select a random task item
2.Click the button to rebind and restore the selection
As a result you will encounter a NullReferenceException.

Workaround: set the SelectedItem property to null/Nothing before rebinding

To reproduce:
- Add enough items so that the vertical scroll is shown.
- Scroll so the first item is not visible.
- Move one of the visible items.

To reproduce: 
 public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();

        this.radGanttView1.GanttViewElement.GraphicalViewElement.TimelineStart = new DateTime(2010, 10, 9);
        this.radGanttView1.GanttViewElement.GraphicalViewElement.TimelineEnd = new DateTime(2010, 12, 10);

        this.FillGanttViewWithData();
    }

    private void radGanttView1_SelectedItemChanged(object sender, GanttViewSelectedItemChangedEventArgs e)
    {
        var dateToFocus = e.Item.Start;
        this.radGanttView1.GanttViewElement.GraphicalViewElement.ScrollTo(dateToFocus);
    }

    private void FillGanttViewWithData()
    {
        //setup data items
        GanttViewDataItem item1 = new GanttViewDataItem();
        item1.Start = new DateTime(2010, 10, 10);
        item1.End = new DateTime(2010, 10, 15);
        item1.Progress = 30m;
        item1.Title = "Summary task.1. title";

        GanttViewDataItem subitem11 = new GanttViewDataItem();
        subitem11.Start = new DateTime(2010, 10, 10);
        subitem11.End = new DateTime(2010, 10, 12);
        subitem11.Progress = 10m;
        subitem11.Title = "Sub-task.1.1 title";

        GanttViewDataItem subitem12 = new GanttViewDataItem();
        subitem12.Start = new DateTime(2010, 10, 12);
        subitem12.End = new DateTime(2010, 10, 15);
        subitem12.Progress = 20m;
        subitem12.Title = "Sub-task.1.2 title";

        //add subitems
        item1.Items.Add(subitem11);
        item1.Items.Add(subitem12);

        this.radGanttView1.Items.Add(item1);

        GanttViewDataItem item2 = new GanttViewDataItem();
        item2.Start = new DateTime(2010, 10, 12);
        item2.End = new DateTime(2010, 10, 18);
        item2.Progress = 40m;
        item2.Title = "Summary task.2. title";

        GanttViewDataItem subitem21 = new GanttViewDataItem();
        subitem21.Start = new DateTime(2010, 10, 12);
        subitem21.End = new DateTime(2010, 10, 13);
        subitem21.Progress = 10m;
        subitem21.Title = "Sub-task.2.1 title";

        GanttViewDataItem subitem22 = new GanttViewDataItem();
        subitem22.Start = new DateTime(2010, 10, 13);
        subitem22.End = new DateTime(2010, 10, 18);
        subitem22.Progress = 30m;
        subitem22.Title = "Sub-task.2.2 title";

        GanttViewDataItem subitem23 = new GanttViewDataItem();
        subitem23.Start = new DateTime(2010, 10, 18);
        subitem23.End = new DateTime(2010, 10, 18);
        subitem23.Title = "Sub-task.2.3 title";

        //add subitems
        item2.Items.Add(subitem21);
        item2.Items.Add(subitem22);
        item2.Items.Add(subitem23);

        this.radGanttView1.Items.Add(item2);

        //add links between items
        GanttViewLinkDataItem link1 = new GanttViewLinkDataItem();
        link1.StartItem = subitem11;
        link1.EndItem = subitem12;
        link1.LinkType = TasksLinkType.FinishToStart;
        this.radGanttView1.Links.Add(link1);

        GanttViewLinkDataItem link2 = new GanttViewLinkDataItem();
        link2.StartItem = subitem21;
        link2.EndItem = subitem22;
        link2.LinkType = TasksLinkType.StartToStart;
        this.radGanttView1.Links.Add(link2);

        GanttViewLinkDataItem link3 = new GanttViewLinkDataItem();
        link3.StartItem = subitem22;
        link3.EndItem = subitem23;
        link3.LinkType = TasksLinkType.FinishToStart;
        this.radGanttView1.Links.Add(link3);

        GanttViewTextViewColumn titleColumn = new GanttViewTextViewColumn("Title");
        GanttViewTextViewColumn startColumn = new GanttViewTextViewColumn("Start");
        GanttViewTextViewColumn endColumn = new GanttViewTextViewColumn("End");

        this.radGanttView1.GanttViewElement.Columns.Add(titleColumn);
        this.radGanttView1.GanttViewElement.Columns.Add(startColumn);
        this.radGanttView1.GanttViewElement.Columns.Add(endColumn);
    }
}

Workaround: 
public class CustomGanttView : RadGanttView
{
    protected override RadGanttViewElement CreateGanttViewElement()
    {
        return new CustomGanttViewElement();
    }

    public override string ThemeClassName
    {
        get { return typeof(RadGanttView).FullName; }
    }
}

public class CustomGanttViewElement : RadGanttViewElement
{
    protected override GanttViewGraphicalViewElement CreateGraphicalViewElement(RadGanttViewElement ganttView)
    {
        return new CustomGanttViewGraphicalViewElement(this);
    }

    protected override Type ThemeEffectiveType
    {
        get { return typeof(RadGanttViewElement); }
    }
}

public class CustomGanttViewGraphicalViewElement : GanttViewGraphicalViewElement
{

    public CustomGanttViewGraphicalViewElement(RadGanttViewElement ganttView)
        : base(ganttView)
    { }

    protected override Type ThemeEffectiveType
    {
        get { return typeof(GanttViewGraphicalViewElement); }
    }

    public override bool ScrollTo(DateTime dateTime)
    {
        if (dateTime < this.TimelineBehavior.AdjustedTimelineStart || dateTime > this.TimelineBehavior.AdjustedTimelineEnd)
        {
            return false;
        }

        float halfViewWidth = (float)this.ViewElement.Size.Width / 2f;
        float x = (float)((dateTime - this.TimelineBehavior.AdjustedTimelineStart).TotalSeconds / this.OnePixelTime.TotalSeconds);
        x -= halfViewWidth;

        if (x < 0)
        {
            this.TimelineScroller.Scrollbar.Value = this.TimelineScroller.Scrollbar.Minimum;
        }
        else if (x > this.TimelineScroller.Scrollbar.Maximum)
        {
            this.TimelineScroller.Scrollbar.Value = this.TimelineScroller.Scrollbar.Maximum - this.TimelineScroller.Scrollbar.LargeChange;
        }
        else
        {
            this.TimelineScroller.Scrollbar.Value = (int)x;
        }

        return true;
    }
}

To reproduce: 
1. Drag and drop RadGanttView
2. Add summary task with 3 sub tasks
3. Set the ReadOnly property to true
4. Run the form and try to move summary task. The user should not be able to move summary task or any other task when is in read only mode. 

Workaround: 
You can set the following properties: 
this.radGanttView1.ReadOnly = true;
this.radGanttView1.AllowSummaryEditing = false;

To reproduce: 
1. Drag and drop RadGanttView on the form
2. Populate with tasks and set the ReadOnly property to true. 
3. Run the application and you will see that you can add links

Workaround: 
Disable adding of links:
void radGanttView2_LinkAdding(object sender, GanttViewLinkAddingEventArgs e)
{
    e.Cancel = true;
}

If one subscribes to the TimelineItemElementCreating and provides custom item elements for the timeline these elements are not used and default item elements are used instead.

WORKAROUND:

Create a custom element provider:

public class CustomGanttViewTimelineElementProvider : GanttViewTimelineElementProvider
{
    public CustomGanttViewTimelineElementProvider(GanttViewGraphicalViewElement owner)
        : base(owner)
        { }

    public override IVirtualizedElement<GanttViewTimelineDataItem> CreateElement(GanttViewTimelineDataItem data, object context)
        {
            GanttViewTimelineItemElement element = this.OnItemElementCreating(data);

            if (element != null)
            {
                return element;
            }

            return new GanttViewTimelineItemElement(data, this.Owner);
        }
}

and assign it to the timeline container element provider:

this.radGanttView1.GanttViewElement.GraphicalViewElement.TimelineContainer.ElementProvider = new CustomGanttViewTimelineElementProvider(this.radGanttView1.GanttViewElement.GraphicalViewElement);