When you do something like

  StringList1.Strings[Index] := Value

it calls TStringList.Put().

I would expect that if Value = Strings[Index] then nothing happens, and no Change or Changing are called.

Muttatis mutandis for PutObject.

Procedure TStringList.Put(Index: Integer; const S: string);
begin
  If Sorted then
    Error(SSortedListError,0);
  If (Index<0) or (INdex>=Fcount)  then
    Error (SListIndexError,Index);
//First check for   Flist^[Index].FString = S, and if so exit?
  Changing;
  Flist^[Index].FString:=S;
  Changed;
end;
Procedure TStringList.PutObject(Index: Integer; AObject: TObject);
begin
  If (Index<0) or (INdex>=Fcount)  then
    Error (SListIndexError,Index);
//First check for Flist^[Index].FObject equals AObject, and if so Exit?
  Changing;
  Flist^[Index].FObject:=AObject;
  Changed;
end;

Of course I might be horribly wrong.
Can someone elaborate on this?

Bart

You expect wrong. No supposition is made whatsoever on the value. Every write in the list triggers a change.

This is how delphi implements it, and that is how we implemented it.

Michael.

Michael Van Canneyt wrote

You expect wrong. No supposition is made whatsoever on the value. Every write in the list triggers a change. This is how delphi implements it, and that is how we implemented it.

That's why I mentioned I might be horribly wrong.
So Delphi compatibility.

I think it's inconsitent with other components that have a OnChange. Generally this is only fired if something (text) "really" changed.

Current behaviour leads to many unneccesary calls to OnChange and OnChanging in a certain Lazarus LCL component (fixed it there).

Thanks for explaining.

Bart

Yes.

I think it's inconsitent with other components that have a OnChange. Generally this is only fired if something (text) "really" changed.

There are many exceptions to that rule.

Current behaviour leads to many unneccesary calls to OnChange and OnChanging in a certain Lazarus LCL component (fixed it there).

I am aware of this.

But the impact of changing it is impossible to guess, so it is not subject to change.

Michael.

Which is fine by me.
I just wondered, and now I'm informed...
And with that new knowledge I can improve my code.

Thanks.

Bart

Glad to be of help :-)

Michael.