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bug#53798: 27.1; OSX: (redisplay) does not reliably redisplay
From: |
Markus Triska |
Subject: |
bug#53798: 27.1; OSX: (redisplay) does not reliably redisplay |
Date: |
Sat, 05 Feb 2022 19:24:28 +0100 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) |
Eli Zaretskii <eliz@gnu.org> writes:
> If you press several keys, you need to call read-char that number of
> time, or empty the input queue in some other way. Otherwise, you
> still have input available after calling read-char, like in the
> original recipe, because you pressed more than one key.
I tried to do this by using as the final form instead:
(while t
(transform-line)
(redisplay)
(while (input-pending-p)
(read-char))
(sit-for 0.1))
This reads characters as long as input-pending-p succeeds, in order to
read all characters that are pending. However, I still can reproduce the
issue.
>
> I'm not on macOS, so I commented out the part of the recipe that deals
> with interprogram-cut-function. When I run the result, I see no
> abnormal behavior, even if I press several keys.
I can reproduce this: When I remove these settings, everything works as
intended. This confirms that these settings are relevant to reproduce
this issue.
> I'm not sure I understand what you are trying to establish with these
> recipes. What is the actual issue you are trying to solve, and why
> the call to redisplay/sit-for and pressing keys are part of that?
The issue I am facing is the following: I have programmed Emacs to
automate several tasks for me. For instance, in the example I posted,
the task is to convert UnicodeData.txt to a collection of Prolog facts
that can be queried and reasoned about with Scryer Prolog. This is an
example of an actual task I am trying to solve. I noticed that when I
start the automation, and then accidentally press a key, the program
seems to stall instead of proceeding as intended, *even* when I take
provisions, within the program, that aim to counteract the stall. For
example, in the sample snippet I posted, I tried to manually enforce a
redisplay by calling (redisplay), and still I do not see a
redisplay. Instead, I see no display update at all for many iterations.
> What do you mean by "how Emacs redisplays things"? In these recipes,
> you actually force Emacs to do redisplay, both by calling 'redisplay'
> and by calling 'sit-for', instead of letting it do it "naturally". So
> I wonder where all this is going, and why.
I am *trying* to force Emacs to redisplay. The issue I am facing is that
the redisplay does *not* happen, even though I am using (redisplay). In
other words, Emacs seems to be active in the sense that it does perform
the operations I ask of it, but it does not show the result even though
I ask them to be shown.
Does this explanation help? Please let me know if there is anything I
can do to help reproduce this.
Thank you a lot!
Markus