GNU bug report logs - #5721
Feature request: Function that returns absolute coordinates

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Message #94 received at 5721 <at> debbugs.gnu.org (full text, mbox):

From: Jan Djärv <jan.h.d <at> swipnet.se>
To: YAMAMOTO Mitsuharu <mituharu <at> math.s.chiba-u.ac.jp>
Cc: 5721 <at> debbugs.gnu.org, IRIE Shinsuke <irieshinsuke <at> yahoo.co.jp>
Subject: Re: bug#5721: Feature request: Function that returns absolute
	coordinates
Date: Thu, 15 Jul 2010 10:59:52 +0200

YAMAMOTO Mitsuharu skrev 2010-07-15 10.44:
>>>>>> On Thu, 15 Jul 2010 10:35:47 +0200, Jan Djärv<jan.h.d <at> swipnet.se>  said:

>> That would require unscaled everywhere, even in pos-x-y, window
>> sizes, font sizes and so on.  I didin't think that was your
>> suggestion.
>
> No, they are all frame-relative, so scaled by the scaling factor.
>
> The only places currently I can think of in the "absolute" category
> are the frame parameters `left' and `top', and some screen parameters
> such as `display-pixel-height', etc.  Most of the values in Lisp are
> designed as frame-relative.

But many operations add and subtract from frame top, left and display 
width/height.  How many?  I don't know, I just suspect that there are many 
based on what I've seen when editing existing lisp files in Emacs.  Not to 
mention C files.

>
>>> Again, if we used absolute scaled coordinates to specify `left' and
>>> `top' frame parameters, we could only place the frame to the
>>> position whose coordinates are multiples of the scale factor.
>
>> As I said earlier, special functions to deal with that for those that care.
>
> I don't understand.  What happens if a user moved the frame to (101,
> 101) using the mouse under the scale factor 2, and he checked
> (frame-parameter nil 'left)?

Is 101 scaled or unscaled?  If scaled, left would be 101.
If not scaled, left would be 50.  Loss of precision? Sure, but does it matter 
in most cases?

Another idea would be if Emacs had its own internal coordinate system, say 0.0 
to 1.0 or some integer based one, that already is display independent.
It would fit nicely with the GnomeCanvas idea (see other thread).
A bunch of work though...

	Jan D.

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