/// <summary>
/// Implements the dropdown style for selecting layers
/// </summary>
/// <param name="context"></param>
/// <param name="provider"></param>
/// <param name="value"></param>
/// <returns></returns>
public override object EditValue(ITypeDescriptorContext context, IServiceProvider provider, object value)
{
// Uses the IWindowsFormsEditorService to display a drop-down UI
if (edSvc == null)
{
edSvc = (IWindowsFormsEditorService)provider.GetService(typeof(IWindowsFormsEditorService));
}
if (edSvc != null)
{
if (listbox == null)
{
listbox = new ListBox();
listbox.BorderStyle = BorderStyle.None;
listbox.SelectedIndexChanged += new EventHandler(OnListBoxChanged);
}
GraphLayerAttribute attr = context.PropertyDescriptor.Attributes[typeof(GraphLayerAttribute)] as GraphLayerAttribute;
GraphLayerCollection values = new GraphLayerCollection();
//attributes are the only way to pass info from the context to the property grid
//A UITypeDescriptor is supposed to be independent of the context/application
//There is no way you can get access to the canvas starting from the grid or from this class
if (attr != null && !attr.IsDefaultAttribute())
{
values.AddRange(attr.Layers);
}
//GraphLayer dl = new GraphLayer("Default");
values.Add(GraphAbstract.DefaultLayer);
//this is only for design-time support:
//ISelectionService serv = (ISelectionService )provider.GetService(typeof(ISelectionService ));
listbox.Items.Clear();
int width = 0;
Font font = listbox.Font;
// Add the standard values in the list box and
// measure the text at the same time.
using (Graphics g = listbox.CreateGraphics())
{
foreach (GraphLayer layer in values)
{
if (!listbox.Items.Contains(layer))
{
// if (!editor.ShowPreviewOnly)
width = (int)Math.Max(width, g.MeasureString(layer.ToString(), font).Width);
listbox.Items.Add(layer);
}
}
}
listbox.SelectedItem = value;
listbox.Height =
Math.Max(font.Height + 2, Math.Min(200, listbox.PreferredHeight));
listbox.Width = Math.Max(width, 100);
edSvc.DropDownControl(listbox);
if (listbox.SelectedItem != null)
{
return(listbox.SelectedItem);
}
else
{
return(value);
}
}
return(value);
}
