By looking at the JvInspector code the OnItemDoubleClicked is fired when there is no item editor (readonly?) and the item is an object property. So this is definitely the wrong event (and its name is misleading).
The problem is that the double click event isn't directed at the JvInspector control but at the current editor control (TEdit, TComboBox, ...). So the JvInspector doesn't see the double click. To solve this you need to hook the editor's OnDblClick event. And for that the JvInspector has the OnBeforeEdit event.
procedure TForm1.JvInspector1BeforeEdit(Sender: TObject; Item: TJvCustomInspectorItem;
Edit: TCustomEdit);
begin
TEdit(Edit).OnDblClick := ItemDblClick;
end;
procedure TForm1.ItemDblClick(Sender: TObject);
begin
ShowMessage(JvInspector1.Selected.Name);
Abort; // don't change the value by the default double click handler
end;
This doesn't work for "Set" properties or other properties that have no editor control.