[Lazarus] Changes to bugreport #33331 completely changes long standing behaviour

[Werner Pamler]

Am 03.04.2018 um 14:41 schrieb Maxim Ganetsky via Lazarus:
> I reopened this bug report. Please comment there.

But since other opinions are required we should discuss here - the bug 
tracker is not the place for discussion. I applied the change leading to 
this issue would like to hear other opinions. Here's what I wrote in bug 
tracker:

"I don't see anything wrong in the logics of the new behavior: The 
OnChanging event is fired before the selected node is changed. It has 
the node which will become the new selected node as a parameter, and you 
can do some validation and signal in AllowChange whether the change to 
the new node will be allowed or not. In the event handler you still have 
access to the currently selected node as TreeView.Selected. Therefore, 
there is no need at all to duplicate the currently selected node in the 
node parameter of the event.

This behavior is now compatible with Delphi (it was not before the fix).

Like any bugfix the new code breaks backward compatibility - sorry for 
the inconvenience if you have relied on the old behavior.

Which other controls have the OnChanging event? I only found 
TPageControl/TTabControl but they don't pass the changing tab as a 
parameter. "