bug#10072: 23.3; invisible text

[Andrew Kurn <kurn@sfu.ca>]

On Sun 20 Nov 2011 15:30 -0500, Stefan Monnier wrote:
> 
> > Let me propose this wording:
> > -----------
[. . .]
> > ---------
> 
> Thanks.  I installed the text below instead (which is closer to what
> really happens).
> 

Sorry, but I didn't receive this latest version.  Could you re-send
it?



> > As an opinion, I add that it would be more intuitive if it worked
> > differently -- the way described in the original example -- but
> > I can live with this once it is clearly explained.  (The problem
> > is, of course, that ^X= should always name a visible character,
> > and the one that the cursor is over.)
> 
> The use of a block cursor that covers the "next visible char" indeed
> tends to make people assume that point is right before that visible
> char, but if you use a different cursor this is much less true.
> 


Agreed.


> In any case the driving factor is to try and avoid the case where
> self-insert-command inserts invisible text, which is also
> very confusing.  Another advantage of the current behavior is that it
> lets the author choose where to place point, by setting
> stickiness appropriately, so you can get Emacs to indeed place the
> cursor right in front of the next visible char.

Yes, I understand your thinking.

Right this moment, I don't have access to the latest version
of Emacs, so I am not sure of the relevance of this remark:
However, I was experimenting with invisibility in overlays
and I found it was possible to insert invisible text.  

I suspect that the philosophy of the command-loop-move-point
thingy is to move point so that invisible text will not be
inserted in /any/ case.  So there's another possible bug.


> 
> >> The code that moves point out of invisible chunks of text does not
> >> always work, indeed, because it is only applied to the current
> >> buffer (or maybe the selected-window?) after a command.
> > Yes, I see.  This might need clarification in the text also.
> 
> Fundamentally it's a bug, and I generally don't like to document bugs.


On this point I disagree with you very strongly.  It's much /more/
important to document bugs than any other aspect of the code.  I have
told several students this from time to time, and, like you, they
tend to resist the idea.

I gather that there is no great push on to remedy this behavior,
so this bug may hang around for some time . . .

Anyhow, I'm pretty happy with my improved understanding, so I'm
grateful for your help.  Are you a volunteer?  I guess that FSF
doesn't have enough money to employ a staff of programmers to
deal with this sort of correspondence.

Andrew