bugfix: regression: cursor jumps to first line on startup

This is a regression caused by

    commit   f68dc7ccb1489dabce1fd3997a7c59e39b23b4ad
    Date:    Tue Aug 29 11:51:07 2023 -0700
    Subject: bugfix: don't use $LINE to initialize basta_scroll_lines.

Issue is that if we initialize basta_scroll_lines to zero,
the basta.check_cursor function reacts to it, and not very
well. It moves the cursor to the top of the screen.

- We add a new function basta.initial_prompt_hook which is
  installed at startup. This function doesn't do any
  processing of the exit status of the previous command (there
  isn't one) and doesn't call basta.check_cursor.

- basta.initial_prompt_hook changes the hook to
  basta.prompt_hook after one call. The basta_scroll_lines
  variable is initialized at that point, so all is well.

- with this approach, there is no added run-time check for
  "is basta_scroll_lines initialized".

1 files changed, 9 insertions, 1 deletions

diff --git a/basta.sh b/basta.sh
index cc2fa0d..ce12a34 100644
--- a/basta.sh
+++ b/basta.sh
@@ -103,6 +103,14 @@ basta.do_exit_status()
   basta_old_cmdno=$cmdno
 }
 
+basta.initial_prompt_hook()
+{
+   local exit=$?
+   stty raw -echo onlcr opost
+   basta.update_status
+   stty sane rows $basta_scroll_lines
+   PROMPT_COMMAND='basta.prompt_hook'
+}
 
 basta.prompt_hook()
 {
@@ -147,7 +155,7 @@ basta.cleanup()
   printf "Basta!\n"
 }
 
-PROMPT_COMMAND='basta.prompt_hook'
+PROMPT_COMMAND='basta.initial_prompt_hook'
 
 if ! [ $basta_status_alarm_pid ] ; then
   trap basta.update_status ALRM