Old zsh change

Old zsh change

[Jeremy Shoup]

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Hi all,

I've recently upgraded my zsh from 4.2.0 to 4.3.10 (by upgrading some
systems from Redhat ES 4 to 6). I've noticed a behaviour change that I
think is related to a very old change to zsh, change 20900 (2005-03-03)
according to the ChangeLog. I wanted to have a look at what that change was
to determine the best way for me to deal with it, but the ChangeLog does
not indicate which source file(s) were affected by that change. I was
wondering if you could tell me what files were changed?

Kind Regards,
Jeremy Shoup

Re: Old zsh change

[Jérémie Roquet]

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Hi,

2013/3/5 Jeremy Shoup <jeremy.shoup@gmail.com>:
> I've recently upgraded my zsh from 4.2.0 to 4.3.10 (by upgrading some
> systems from Redhat ES 4 to 6). I've noticed a behaviour change that I
> think is related to a very old change to zsh, change 20900 (2005-03-03)
> according to the ChangeLog. I wanted to have a look at what that change was
> to determine the best way for me to deal with it, but the ChangeLog does
> not indicate which source file(s) were affected by that change. I was
> wondering if you could tell me what files were changed?

20900 is a FAQ change, see attached patch.

Best regards,

-- 
Jérémie

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commit a50c752448392ce503e37c968f8cf183923dcd39
Author: Peter Stephenson <pws@users.sourceforge.net>
Date:   Thu Mar 3 10:29:22 2005 +0000

    20900, adapted: promptcr workaround

diff --git a/ChangeLog b/ChangeLog
index cdc7712..2655737 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2005-03-03  Peter Stephenson  <pws@csr.com>
+
+	* from Wayne, adapted: 20900: another way of preventing
+	text without a newline from being overwritten by the prompt.
+	(Originally suggested by Karl Chen in 20896.)
+
 2005-03-02  Clint Adams  <clint@zsh.org>
 
 	* 20906: Completion/Unix/Command/_make: patch from
diff --git a/Etc/FAQ.yo b/Etc/FAQ.yo
index e9798c9..0f2fc19 100644
--- a/Etc/FAQ.yo
+++ b/Etc/FAQ.yo
@@ -1667,15 +1667,31 @@ sect(How do I prevent the prompt overwriting output when there is no newline?)
     % echo -n foo
     % 
   )
-  and the tt(foo) has been overwritten by the prompt tt(%).  The answer is
-  simple:  put tt(unsetopt promptcr) in your tt(.zshrc).  The option \
-  tt(PROMPT_CR),
-  to print a carriage return before a new prompt, is set by default because
-  a prompt at the right hand side (mytt($RPROMPT), mytt($RPS1)) will not appear
-  in the right place, and multi-line editing will be confused about the line
-  position, unless the line starts in the left hand column.  Apart from
-  tt(PROMPT_CR), you can force this to happen by putting a newline in the
-  prompt (see question link(3.13)(313) for that).
+  and the tt(foo) has been overwritten by the prompt tt(%).  The reason this
+  happens is that the option tt(PROMPT_CR) is enabled by default, and it
+  outputs a carriage return before the prompt in order to ensure that the
+  line editor knows what column it is in (this is needed to position the
+  right-side prompt correctly (mytt($RPROMPT), mytt($RPS1)) and to avoid screen
+  corruption when performing line editing).  If you add tt(unsetopt promptcr)
+  to your tt(.zshrc), you will see any partial output, but your screen may
+  look weird until you press return or refresh the screen.
+
+  Another solution for many terminals is to define a precmd function that
+  outputs a screen-width of spaces, like this:
+  verb(
+    function precmd {
+      echo -n ${(l:$COLUMNS:::):-}
+    }
+  )
+  (Explanation: an empty parameter expansion is padded out to the number of
+  columns on the screen.)  That precmd function will only bump the screen
+  down to a new line if there was output on the prompt line, otherwise the
+  extra spaces get removed by the tt(PROMPT_CR) action.  Although this
+  typically looks fine it may result in the preceding spaces being included
+  when you select a line of text with the mouse.
+
+  One final alternative is to put a newline in your prompt -- see question
+  link(3.13)(313) for that.
 
 
 sect(What's wrong with cut and paste on my xterm?)

Re: Old zsh change

[Wayne Davison]

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On Tue, Mar 5, 2013 at 9:24 AM, Jeremy Shoup <jeremy.shoup@gmail.com> wrote:

> I've recently upgraded my zsh from 4.2.0 to 4.3.10 (by upgrading
> some systems from Redhat ES 4 to 6). I've noticed a behaviour change that
> I think is related to a very old change to zsh, change 20900
> (2005-03-03) according to the ChangeLog.


It sounds like you may be referring to the PROMPT_SP option, which the FAQ
entry for question 3.23 intros as follows:

[Prompt overwriting of output] is normally limited to zsh versions prior to
4.3.0 due to the advent of the PROMPT_SP option (which is enabled by
default, and eliminates this problem for most terminals).

If you don't like the way prompt_sp works, that FAQ entry also details a
work-alike function that can be run from precmd, which you could customize
and use instead.

..wayne..