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bug#37213: Execute set-window-margins. left-margin-width remains 0.
From: |
Alan Mackenzie |
Subject: |
bug#37213: Execute set-window-margins. left-margin-width remains 0. |
Date: |
Sat, 31 Aug 2019 14:07:36 +0000 |
User-agent: |
Mutt/1.10.1 (2018-07-13) |
Hello, Martin.
On Thu, Aug 29, 2019 at 09:46:54 +0200, martin rudalics wrote:
> > The documentation says "This variable specifies the width of the left
> > margin". As best, this is unclear. What you're saying is that the
> > variable ceases to specify that width, should the margin be altered by
> > other means.
> Eli didn't say that.
> > I maintain that this is either a bug in the documentation, or in the
> > code.
> > If the former, it should explicitly state that the variable is
> > write-only, and its read value is undefined. It should say that the
> > function window-margins should be used instead.
> The variable is not write-only and its read value is well-defined.
Is the read value well-defined? Never having set it, the value it has
seems always to be 0. But even if it is well-defined, is it useful for
anything?
> > But it might be easier just to amend the code. There appear to be just
> > two ways to set the width of the left margin (or the right margin), so
> > if it gets set the second way, why not just set that variable? Could
> > this do any harm? (Note: I haven't looked at the code, yet.)
> Please re-read the documentations of 'left-margin-width' and
> 'set-window-margins' having in mind that the same buffer may appear in
> different windows and the same window may show different buffers all
> with differing margins.
Yes, that's the thing. We don't have "window local variables" in Emacs,
so anything specific to a window needs a function interface with the
window being one of the parameters.
> Once you've done that, please look at the respective documentations
> for fringes and scroll bars which are even more complicated because
> they have to obey a frame parameter as well.
I've proposed a simple amendment to the "Display Margins" page of the
elisp manual, saying "don't use these variables to ....!". This would
solve the misunderstanding I experienced earlier.
> Thanks, martin
--
Alan Mackenzie (Nuremberg, Germany).
bug#37213: Execute set-window-margins. left-margin-width remains 0., martin rudalics, 2019/08/29
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