GNU bug report logs - #50256
thing-at-mouse

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From: martin rudalics <rudalics <at> gmx.at>
To: Eli Zaretskii <eliz <at> gnu.org>
Cc: 50256 <at> debbugs.gnu.org, larsi <at> gnus.org, juri <at> linkov.net
Subject: bug#50256: thing-at-mouse
Date: Thu, 2 Sep 2021 08:48:15 +0200

> Then what is the semantics of the code snippet above, and why did you
> call with-current-buffer the second time?  What did you want to
> accomplish, except make a point?

I tried to write a simple example with emacs -Q showing how code breaks
a contract stated in a manual.

> IOW, what kind of real-life situation needs such a code?

Any call of `pos-visible-in-window-p' might happen within the context of
`with-current-buffer'.  Just check how often these forms are used in the
Emacs code base.

>> (pos-visible-in-window-p nil nil t) should never return nil as it
>> does in the above recipe.
>
> Why not?

Because in the manual we say that

  "The argument POSITION defaults to the current position
   of point in WINDOW; WINDOW defaults to the selected window."

If the current buffer is not shown in WINDOW, the first part of this
sentence is wrong.

martin

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