hack: do cursor check only if no input pending

I'm addressing the following problem. Sometimes the user types
a new command while a previous command is still running. This
typed-ahead input is buffered in the TTY. When we execute our
check to query the terminal "is the cursor out of bounds?"
there is a conflict between that buffered input and the query.
An imperfect fix is to check for the presence of unread input
and skip doing the cursor check.

This means that if the user runs some program that puts the
cursor out of bounds, and impatiently types ahead before
that command has completed, the cursor will go out of bounds.

- We break the basta.before_prompt function into two:
  basta.check_cursor and basta.do_exit_status.

- In basta.check_cursor, we now temporarily put the TTY into
  raw mode, so that the file descriptor can be polled for
  the presence of any bytes whatsoever. If we don't do this,
  read -t 0 will only report true (input is present) if
  the user has typed Enter, due to canonical input processing.

1 files changed, 24 insertions, 9 deletions

diff --git a/basta.sh b/basta.sh
index 1b52c07..1c8fe93 100644
--- a/basta.sh
+++ b/basta.sh
@@ -68,18 +68,30 @@ basta.update_status()
   printf "${esc}7$esc[%s;1H$esc[K%s$esc[1;%sr${esc}8" $((LINES + 1)) "$status" $LINES
 }
 
-basta.before_prompt()
+basta.check_cursor()
 {
-  local exit=$?
-  local esc=$(printf "\033")
-  local curln=$(basta.get_cur_line)
-  local getcmdno='\#'
-  local cmdno=${getcmdno@P}
+  local saved_tty=$(stty -g)
+  stty raw
 
-  if [ $curln -gt $LINES ]; then
-    printf "$esc[%s;1H" $LINES
+  if ! read -t 0; then
+    local exit=$?
+    local esc=$(printf "\033")
+    local curln=$(basta.get_cur_line)
+
+    if [ $curln -gt $LINES ]; then
+      printf "$esc[%s;1H" $LINES
+    fi
   fi
 
+  stty "$saved_tty"
+}
+
+basta.do_exit_status()
+{
+  local exit=$1
+  local getcmdno='\#'
+  local cmdno=${getcmdno@P}
+
   if [ $exit -ne 0 -a $cmdno -ne $basta_old_cmdno ] ; then
     printf "!%s!\n" $exit
   fi
@@ -87,9 +99,12 @@ basta.before_prompt()
   basta_old_cmdno=$cmdno
 }
 
+
 basta.prompt_hook()
 {
-   basta.before_prompt
+   local exit=$?
+   basta.check_cursor
+   basta.do_exit_status $exit
    basta.update_status
 }