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Re[2]: bash 4.3: "Clear Scrollback and Reset" (Ctrl-Shift-X) in konsole

From: Askar Safin
Subject: Re[2]: bash 4.3: "Clear Scrollback and Reset" (Ctrl-Shift-X) in konsole stopped to work as expected when upgrading from upstream bash 4.2 to upstream bash 4.3
Date: Sat, 29 Nov 2014 01:38:20 +0300

>There are only a couple of ways to do this, so even though the mechanism
>konsole uses is undocumented, we can try to figure it out.  There are two
>possibilities: inject a character into the input stream, or send a signal
>to the foreground process group.
I tested this. This is not some symbol in input stream (tested using "stty raw 
-echo; cat > /tmp/log"). And this is signal 28, i. e. SIGWINCH (on Debian 
GNU/Linux amd64, tested using small C program). Also, a small test C program, 
which uses readline (Debian version 6.2+dfsg-0.1) works as I expect.

So, yes, this is not bash+konsole bug, this is readline+konsole bug.
>Since typing ^L at the prompt works, that's probably not what konsole uses.
Yes, ^L works.

Also, konsole 2.8.4 (upstream version, default in wheezy) (this is version I 
use) uses Ctrl-Shift-X as default shortcut for "Clear Scrollback and Reset" and 
konsole 2.14.2 (upstream version, default in sid as on today) uses Ctrl-Shift-K.

>This would make sense if the two operations did the same thing. I don't
>think they do; I think the Ctrl-Shift-X key sequence causes konsole to
I still want Ctrl-Shift-X to work as in 4.2. ^_^

>There is a better explanation in one of the threads I referenced in my
>previous message, but here's the short story: readline has always set
>SIGWINCH to restart system calls. It would redraw the prompt upon receipt
>of a SIGWINCH in previous versions because it (incorrectly) executed that
>code in a signal handler context. Cleaning up the code so it didn't try
>to execute arbitrary code in signal handlers was one of the big changes
>between bash-4.2/readline-6.2 and bash-4.3/readline-6.3.
So, is this possible to restore old behavior in bash-4.3/readline-6.3 
preserving "clean" and "right" code?

ATTENTION! Now I want to report some REAL BUG! When I change konsole size with 
some long text line typed in bash 4.2 buffer, text moves. With bash 4.3 it 
doesn't move. :)
Yes, I know, nobody uses Ctrl-Shift-X except for me, so, you think this 
Ctrl-Shift-X-bug isn't worth fixing. But everybody resize his terminal window, 
so now I found real bug, ahaha! :)
Reproduces using 4.3-11 from Debian and doesn't reproduce using 
4.2+dfsg-0.1+deb7u3 from Debian. And thank you, Chet for the idea. :)

Askar Safin
Kazan, Russia

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