Thanks everybody, and esp. for the code sample!
I'm confused. Okay, I did manage to detect what I did wrong, although I did it on purpose because it shouldn't lead to this behaviour.
Well, as you all stated, it is not the TListBox.Items.Add(S: String) that triggers TListBoxSelectionChange, but pls check the next line of my code:
TexListBox.Items.Add(S: String);
TexListBox.ItemIndex := i;
So what actually triggers TListBoxSelectionChange, is the allocation of i (counting var in a for-loop) to the item index (read/write property). How is this triggering TListBoxSelectionChange? - To be clear, as soon as I comment out the second line, everything works as expected. Anyway, in my case I need to make sure the item indices are set as shown. Any explanations and/or ideas?
Just to share the infos as requested: Win8.1-32bit, Laz 1.6.4, FPC 3.0.0.
EDIT: See attached file.