I checked it again with AllowCellEdit property set to ReadOnly. It turned out that what you wrote is true when the TextBox has focus and displays a prompt char, but it requires user to click first on a text and then on editors' associated button.

Is there any other way of adding a CLICKABLE button to a tree cell besides implementing a custom EmbbedableEditor? If there isn't any could you give me some tips how to implement such editor?

ps. I'm using NetAdvantage v8.3 (2021).

Regards,
Pawel

Yes, I see now that you did mention you wanted the button to cover the whole cell, sorry I rushed over that part. I was able to hack this out by changing AllowCellEdit as the cell goes in an out of edit mode:

EditorWithText editor = new EditorWithText();
column.Editor = editor;
editor.ButtonsLeft.Add(button);
editor.BeforeEnterEditMode += new CancelEventHandler(editor_BeforeEnterEditMode);
editor.BeforeExitEditMode += new BeforeExitEditModeEventHandler(editor_BeforeExitEditMode);
editor.EditorButtonClick += new Infragistics.Win.UltraWinEditors.EditorButtonEventHandler(editor_EditorButtonClick);          

void editor_BeforeExitEditMode(object sender, BeforeExitEditModeEventArgs e)
{
    EmbeddableEditorBase editor = sender as EmbeddableEditorBase;
    this.OnEditModeChanged( editor, false );
}

void editor_BeforeEnterEditMode(object sender, CancelEventArgs e)
{
    EmbeddableEditorBase editor = sender as EmbeddableEditorBase;
    this.OnEditModeChanged( editor, true );
}

private void OnEditModeChanged( EmbeddableEditorBase editor, bool entering )
{
    EmbeddableUIElementBase embeddableElement = editor != null ? editor.ElementBeingEdited : null;
    UltraTreeNodeCellUIElement cellElement = embeddableElement.GetAncestor( typeof(UltraTreeNodeCellUIElement) ) as UltraTreeNodeCellUIElement;
    if ( cellElement != null )
        cellElement.Column.AllowCellEdit = entering ? AllowCellEdit.ReadOnly : AllowCellEdit.Full;
}

Thanks for the workaround, works like a charm!

Regards,

Pawel