* usr/bin/byobu, usr/bin/byobu-janitor, usr/lib/byobu/include/common,

usr/lib/byobu/include/constants:
  - for users upgrading from an older version of byobu, where they were
    previously using a screen backend, keep them using a screen backend
  - for new users, default to tmux backend

debian/changelog

@@ -26,6 +26,11 @@ byobu (5.3) unreleased; urgency=low
     - support LC_TERMTYPE=[byobu|byobu-screen|byobu-tmux]
   * etc/profile.d/Z97-byobu.sh, usr/bin/byobu-launcher: LP: #897711
     - allow nesting, if LC_BYOBU > 1
+  * usr/bin/byobu, usr/bin/byobu-janitor, usr/lib/byobu/include/common,
+    usr/lib/byobu/include/constants:
+    - for users upgrading from an older version of byobu, where they were
+      previously using a screen backend, keep them using a screen backend
+    - for new users, default to tmux backend
 
   [ Dustin Kirkland and Ryan Thompson ]
   * usr/bin/byobu-reconnect-sockets, usr/bin/byobu-select-session: LP: #908944

usr/bin/byobu

@@ -31,12 +31,6 @@ if [ ! -O "$HOME" ]; then
 	exit 1
 fi
 
-# Determine backend as early as possible, if applicable
-case "$0" in
-	*byobu-screen) BYOBU_BACKEND="screen" ;;
-	*byobu-tmux) BYOBU_BACKEND="tmux" ;;
-esac
-
 # Source local byobu config
 if [ -r "$HOME/.byoburc" ]; then
 	# Ensure that this configuration is usable
@@ -55,6 +49,12 @@ fi
 [ -z "${BYOBU_PREFIX}" ] && export BYOBU_PREFIX="/usr" || export BYOBU_PREFIX
 . "${BYOBU_PREFIX}/lib/${PKG}/include/common"
 
+# Override backend if we can determine intentions from argv[0]
+case "$0" in
+	*byobu-screen) BYOBU_BACKEND="screen" ;;
+	*byobu-tmux) BYOBU_BACKEND="tmux" ;;
+esac
+
 # At this point, we're sure BYOBU_BACKEND is properly defined
 export BYOBU_BACKEND
 

usr/bin/byobu-janitor

@@ -68,6 +68,7 @@ MC=0
 [ -r "$BYOBU_CONFIG_DIR/profile.tmux" ] || echo "source \$BYOBU_PREFIX/share/$PKG/profiles/tmux" > "$BYOBU_CONFIG_DIR/profile.tmux"
 [ -r "$BYOBU_CONFIG_DIR/keybindings" ] || echo "source \$BYOBU_PREFIX/share/$PKG/keybindings/common" > "$BYOBU_CONFIG_DIR/keybindings"
 [ -r "$BYOBU_CONFIG_DIR/windows" ] || touch "$BYOBU_CONFIG_DIR/windows"
+[ -r "$BYOBU_CONFIG_DIR/backend" ] || echo "BYOBU_BACKEND=$BYOBU_BACKEND" > "$BYOBU_CONFIG_DIR/backend"
 [ -r "$HOME/.screenrc" ] || touch "$HOME/.screenrc"
 [ -r "$BYOBU_CONFIG_DIR/.tmux.conf" ] || touch "$BYOBU_CONFIG_DIR/.tmux.conf"
 for f in status statusrc; do

usr/lib/byobu/include/common

@@ -28,12 +28,22 @@ if [ -z "${BYOBU_INCLUDED_LIBS}" ]; then
 		[ -r "$BYOBU_CONFIG_DIR/backend" ] && . "$BYOBU_CONFIG_DIR/backend"
 		# Just in case there's no config file at all
 		if [ -z "${BYOBU_BACKEND}" ]; then
-			# If tmux is installed, use it
-			if command -v tmux >/dev/null; then
-				BYOBU_BACKEND=tmux
-			elif command -v screen >/dev/null; then
-				BYOBU_BACKEND=screen
+			if [ -d "$BYOBU_CONFIG_DIR" ] && [ -r "$BYOBU_CONFIG_DIR/profile" ]; then
+				# Previous byobu configuration exists, default to screen
+				for i in screen tmux; do
+					command -v $i >/dev/null && BYOBU_BACKEND="$i"
+					break
+				done
+				unset i
 			else
+				# New byobu configuration, default to tmux
+				for i in tmux screen; do
+					command -v $i >/dev/null && BYOBU_BACKEND="$i"
+					break
+				done
+				unset i
+			fi
+			if ! command -v "$BYOBU_BACKEND" >/dev/null; then
 				echo "ERROR: $PKG won't work without tmux or screen installed" 1>&2
 			fi
 		fi

usr/lib/byobu/include/constants

@@ -86,7 +86,7 @@ case "$BYOBU_BACKEND" in
 		BYOBU_ARG_VERSION="-V"
 		ESC=
 	;;
-	*)
+	screen)
 		export BYOBU_BACKEND="screen"
 		BYOBU_ARG_VERSION="-v"
 		ESC="\005"