Subject: Re: bug#18195: 24.3.92; window-screen-lines is not accurate

From: Eli Zaretskii <[email-masked]>
Date: Tue, 05 Aug 2014 16:57:21 +0300

> Date: Tue, 05 Aug 2014 14:24:59 +0400
> From: Dmitry Gutov <[email-masked]>
> 
> `count-screen-lines' already helps with "space above the current line", 
> and we can find out the total height of the window in pixels.

How do you convert the line count returned by count-screen-lines into
pixels, if the lines are of non-constant height.

Also note the caveats in the doc string of that function: the value is
not 100% reliable.

> So if I'm going to do the arithmetics myself, the one thing missing
> is the accurate value of the height of a line in the buffer.

Line of what font?

> The docstring of `window-screen-lines' seems to claim that it's 
> suitable. The implementation looks kinda right, too, but the result it 
> returns is not accurate.

It is accurate now.  But, as I wrote elsewhere in this thread, that
will only solve some of your problems.  In general, we don't support
layout of arbitrary text from Lisp.