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Re: Making Emacs Lisp easier to debug
From: |
Alan Mackenzie |
Subject: |
Re: Making Emacs Lisp easier to debug |
Date: |
Sat, 11 Nov 2023 14:56:17 +0000 |
Hello, Eli.
On Sat, Nov 11, 2023 at 15:47:51 +0200, Eli Zaretskii wrote:
> > Date: Sat, 11 Nov 2023 12:10:33 +0000
> > Cc: emacs-devel@gnu.org
> > From: Alan Mackenzie <acm@muc.de>
> > > (I also don't understand why you think this will help with font-lock,
> > > nor even how it would work in general, should it be possible.
> > With font lock, or any other Lisp hook called from redisplay, it should
> > be possible, in a recursive-edit loop, to run edebug, displaying on a
> > different frame. That different frame would be running in the inner
> > redisplay while the outer redisplay would be suspended.
> Why do you need an inner redisplay for that?
Because the outer redisplay would be the thing being debugged, and hence
not in a position to display the progress of edebug.
> And what will that frame show, given that the outer redisplay is
> halfway through fontifying the text? what do you expect to see there,
> and why?
I think the scope of a redisplay operation could change from everything
to a single frame. So in normal operation a high level routine would
call redisplay2 for each of Emacs's frames in turn.
While stepping through a hook in edebug in the inner redisplay, the
outer redisplay would (I think) carry on looking like it did before the
outer redisplay started. Or, possibly, it might look like a bare frame,
I'm not sure.
> > > Re-entering redisplay in the middle of a redisplay cycle means that
> > > the outer redisplay didn't finish preparing the glyph matrices, and
> > > what do you want the inner redisplay to do in such a case?
> > Work with the glyph matrices belonging to the inner redisplay whilst the
> > outer one is suspended.
> But that will immediately get you into the same problem, since the
> offending window will get redisplayed by the inner redisplay, and will
> again cause Edebug, etc., ad nauseam.
We could put a limit on the nesting depth of redisplay nesting that
edebug would cope with, a small integer (2 or 3, probably). That is
very similar to what edebug currently does during a redisplay, i.e. it
bypasses edebug's processing entirely.
> > As I say, it is not clear whether or not this is possible or
> > practicable. If it were, we could enhance edebug such that a function
> > in a font lock pattern, or on, say, window-scroll-functions could be
> > edebugged by doing nothing more than instrumenting it with C-u C-M-x.
> > Thus Lisp called from redisplay would cease to be an awkward special
> > case as far as debugging is concerned.
> I think we should start by having a clear idea of what should such an
> "inner redisplay" show and how, before we are talking about
> implementing it.
I agree.
> My impression from what you wrote is that the idea is way too vague to
> discuss the details, ....
Yes. It's currently just a vague idea, and it's not even clear as yet
whether it's practicable. But if it is, I think it would be worthwhile
implementing.
> .... and what you call "inner redisplay" is not what you want at all.
I don't understand why you say this. Do you see any particular problems
with it (in addition to what you've already written), or perhaps have a
better scheme for running edebug on redisplay's several Lisp hooks?
--
Alan Mackenzie (Nuremberg, Germany).
- Making Emacs Lisp easier to debug, Alan Mackenzie, 2023/11/10
- Re: Making Emacs Lisp easier to debug, Eli Zaretskii, 2023/11/11
- Re: Making Emacs Lisp easier to debug, Ihor Radchenko, 2023/11/11
- Re: Making Emacs Lisp easier to debug, Alan Mackenzie, 2023/11/11
- Re: Making Emacs Lisp easier to debug, Eli Zaretskii, 2023/11/11
- Re: Making Emacs Lisp easier to debug, Alan Mackenzie, 2023/11/11
- Re: Making Emacs Lisp easier to debug, Eli Zaretskii, 2023/11/11
- Re: Making Emacs Lisp easier to debug,
Alan Mackenzie <=
- Re: Making Emacs Lisp easier to debug, Eli Zaretskii, 2023/11/11
- Re: Making Emacs Lisp easier to debug, Alan Mackenzie, 2023/11/11
- Re: Making Emacs Lisp easier to debug, Eli Zaretskii, 2023/11/11
- Re: Making Emacs Lisp easier to debug, Alan Mackenzie, 2023/11/11
- Re: Making Emacs Lisp easier to debug, Eli Zaretskii, 2023/11/12
- Re: Making Emacs Lisp easier to debug, Alan Mackenzie, 2023/11/12
- Re: Making Emacs Lisp easier to debug, Eli Zaretskii, 2023/11/12
- XY Problems (tangent, related to common discussion issue here), chad, 2023/11/13