> From: Philippe Verdy <[email protected]> > Date: Mon, 12 Nov 2012 21:07:27 +0100 > Cc: Наталія Базь <[email protected]>, > Unicode Mailing List <[email protected]> > > Is is REALLY enough. > > Simply because these carets are **oriented** and are showing the direction > of insertion or ovewrite when you'll type text. > > It is independant of the fact that you will later insert or delete > characters (generally, editors map the DELETE key fo delete the character > AFTER the insertion point, and the BACKSPACE key to delete the character > BEFORE the insertion point). The key here is AFTER and BEFORE, which is > unambiguous as means the contextual ordering in the backing store of > encoded plain text. The BiDi algorithm helps determining if AFTER and > BEFORE mean either LEFT or RIGHT (the direction shown by the caret).
The UBA indeed tells that, but forcing users to run the UBA mentally, or actually reverse-engineer it to reconstruct the original logical order in the backing store, will not be appreciated by those users. Once again: the editor (a program) will have no problems doing whatever it needs to do, be it insertion or deletion. But the user will have hard time anticipating in advance what effect(s) and in what locuses each of these operations will produce, unless she is cued by showing both possible places. And no, the editor will _not_ know which of these two places to show in advance, because the editor does not know in advance which key will the human press. Anyway, these issues are well known since long ago to people who actually use these scripts, see, for example http://docs.oracle.com/javase/tutorial/2d/text/textlayoutbidirectionaltext.html
