Re: Severe lossage from unread-command-events

[David Kastrup <dak@gnu.org>]

David Kastrup <dak@gnu.org> writes:

> Eli Zaretskii <eliz@gnu.org> writes:
>
>>> From: David Kastrup <dak@gnu.org>
>>> Date: Wed, 05 Aug 2015 17:46:50 +0200
>>> 
>>> run the included test file using
>>> 
>>> emacs -Q -l timer-test.el
>>> 
>>> and then open the generated dribble file /tmp/mydrib.  On my computer,
>>> it looks something like
>>> 
>>> 0000000000000000001111111111111111111222222222222222222223333333333333333444444444444444444555555555555555556666666666666666667777777777777777778888888888888888899999999999999999
>>> 
>>> which means that of 4000 events having an effect in the scratch buffer,
>>> about 5% (a non-deterministic amount) are actually recorded in the
>>> dribble file.  In particular, it looks like only the first of several
>>> events placed into unread-command-events at one point of time will ever
>>> see the dribble file.  While I am only moderately interested in actually
>>> generating a useful dribble file, the same holds for macro recording.
>>> And I have an actual application which is severely impacted here.
>>> 
>>> Note that _all_ of the events (usually) are actually processed as input
>>> in the *scratch* buffer.  It is only the recording of them which falls
>>> really, really flat on its face.
>>
>> My reading of the code in read_char is that when we consume events
>> from unread-command-events, we don't always record the events we find
>> there.
>
> Well, according to how I read the variable description of
> unread-command-events, some are bounced back there from input which has
> already been recorded.  The description reads:
>
>     Documentation:
>     List of events to be read as the command input.
>     These events are processed first, before actual keyboard input.
>     Events read from this list are not normally added to ‘this-command-keys’,
>     as they will already have been added once as they were read for the
>     first time.
>     An element of the form (t . EVENT) forces EVENT to be added to that list.
>
> My test programs used (t . EVENT) after just using EVENT did not do the
> trick either.  However, I don't think most of the other uses of
> unread-command-events I have seen bother doing so.  It might or might
> not be a red herring.
>
>> Does the following naïve attempt at fixing this give good results?  If
>> not, can you tell why not, or show a test case where it misbehaves?
>
> I'll be giving it a try.  The code in keyboard.c is complex to a degree
> where I do not trust myself to venture a guess regarding the nature of
> the right fix.  Or whether the code is in need of reorganization before
> one can hope to get it right anyway.

Another data point would be Artur Malabarba's message about executing
keyboard macros which I answered in
<URL:http://lists.gnu.org/archive/html/emacs-devel/2015-08/msg00100.html>.

From glancing over your proposed fix, it's very much focused on dealing
with recording only.  Which has the advantage of not causing changes
elsewhere.  Artur's message, however, would suggest that there might be
a necessity for changes elsewhere.  I have no idea whether those changes
would be related or concern the same code.  I just wanted to bring this
up while I remember.  Artur's original report stated that he "noticed"
the problems "recently".  If that means that they started _occuring_
recently, they are probably an unrelated issue.

-- 
David Kastrup