How to add a temporary blank line at the end of buffer safely

How to add a temporary blank line at the end of buffer safely

[tumashu]

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> Date: Mon, 11 Dec 2017 16:29:16 +0800 (CST)
> From: tumashu  <address@hidden>
> Cc: "address@hidden" <address@hidden>
>
> by the way, does emacs has a function, which can get the point's left-bottom 
> pixel position,  if not,
> is it possible to add it to emacs?

Doesn't vertical-motion fit the bill?  If not, why not?
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@Eli Zaretskii Thanks for your suggestion, it works very well,  the only problem is that

it can not work when point at the end line of buffer, I use the below code to handle this problem,

(add a temp "\n" then remove) but it seem to hacky.  any good way to solve this problem:


  (if (= (line-end-position) (point-max))
      (let (posn)
        (goto-char (point-max))
        (insert "\n")
        (setq posn (posn-at-point (point) window))
        (delete-char -1)
        posn)
    (vertical-motion 1)
    (posn-at-point (point) window))





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Re: How to add a temporary blank line at the end of buffer safely

[Eli Zaretskii]

> Date: Thu, 11 Jan 2018 16:45:43 +0800 (CST)
> From: tumashu <tumashu@163.com>
> 
> Doesn't vertical-motion fit the bill?  If not, why not?
> ------------------------------------------------------------------------
> @Eli Zaretskii Thanks for your suggestion, it works very well,  the only problem is that 
> it can not work when point at the end line of buffer, I use the below code to handle this problem, 
> (add a temp "\n" then remove) but it seem to hacky.  any good way to solve this problem:

Something like the below, perhaps?

  (aref (font-info (font-at POS)) 3)

This will give you the height of the font used at position POS.  Then
you could add that to the y-coordinate of the line at EOB, to get the
bottom y-coordinate of that line.  (Caveat: font-at doesn't like to be
called at EOB, so make sure you are one buffer position before that.)

Re:Re: How to add a temporary blank line at the end of buffer safely

[tumashu]

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It works, thanks very much.


At 2018-01-12 00:03:51, "Eli Zaretskii" <eliz@gnu.org> wrote:
>> Date: Thu, 11 Jan 2018 16:45:43 +0800 (CST)
>> From: tumashu <tumashu@163.com>
>> 
>> Doesn't vertical-motion fit the bill?  If not, why not?
>> ------------------------------------------------------------------------
>> @Eli Zaretskii Thanks for your suggestion, it works very well,  the only problem is that 
>> it can not work when point at the end line of buffer, I use the below code to handle this problem, 
>> (add a temp "\n" then remove) but it seem to hacky.  any good way to solve this problem:
>
>Something like the below, perhaps?
>
>  (aref (font-info (font-at POS)) 3)
>
>This will give you the height of the font used at position POS.  Then
>you could add that to the y-coordinate of the line at EOB, to get the
>bottom y-coordinate of that line.  (Caveat: font-at doesn't like to be
>called at EOB, so make sure you are one buffer position before that.)

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