From 74773bed62fc232f4574b73a2b5d0fca2e739029 Mon Sep 17 00:00:00 2001
From: Bruno Sutic <bruno.sutic@gmail.com>
Date: Tue, 7 Jul 2015 23:57:11 +0200
Subject: [PATCH] Save pane contents only if pane not blank

---
 CHANGELOG.md       |  2 ++
 scripts/helpers.sh |  5 +++++
 scripts/restore.sh |  9 ++++++---
 scripts/save.sh    | 28 +++++++++++++++++++++++++---
 4 files changed, 38 insertions(+), 6 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index cbf963c..fab2799 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,6 +10,8 @@
 - bugfix for pane contents restoration
 - expand tilde char `~` if used with `@resurrect-dir`
 - do not save empty trailing lines when pane content is saved
+- do not save pane contents if pane is empty (only for 'save pane contents'
+  feature)
 
 ### v2.4.0, 2015-02-23
 - add "tmux-test"
diff --git a/scripts/helpers.sh b/scripts/helpers.sh
index b897d9d..146ab71 100644
--- a/scripts/helpers.sh
+++ b/scripts/helpers.sh
@@ -92,6 +92,11 @@ pane_contents_file() {
 	echo "$(resurrect_dir)/pane_contents-${pane_id}"
 }
 
+pane_contents_file_exists() {
+	local pane_id="$1"
+	[ -f "$(pane_contents_file "$pane_id")" ]
+}
+
 resurrect_history_file() {
 	local pane_id="$1"
 	echo "$(resurrect_dir)/bash_history-${pane_id}"
diff --git a/scripts/restore.sh b/scripts/restore.sh
index a1f48bf..dceaa01 100755
--- a/scripts/restore.sh
+++ b/scripts/restore.sh
@@ -117,7 +117,8 @@ new_window() {
 	local window_name="$3"
 	local dir="$4"
 	local pane_index="$5"
-	if is_restoring_pane_contents; then
+	local pane_id="${session_name}:${window_number}.${pane_index}"
+	if is_restoring_pane_contents && pane_contents_file_exists "$pane_id"; then
 		local pane_creation_command="$(pane_creation_command "$session_name" "$window_number" "$pane_index")"
 		tmux new-window -d -t "${session_name}:${window_number}" -n "$window_name" -c "$dir" "$pane_creation_command"
 	else
@@ -131,7 +132,8 @@ new_session() {
 	local window_name="$3"
 	local dir="$4"
 	local pane_index="$5"
-	if is_restoring_pane_contents; then
+	local pane_id="${session_name}:${window_number}.${pane_index}"
+	if is_restoring_pane_contents && pane_contents_file_exists "$pane_id"; then
 		local pane_creation_command="$(pane_creation_command "$session_name" "$window_number" "$pane_index")"
 		TMUX="" tmux -S "$(tmux_socket)" new-session -d -s "$session_name" -n "$window_name" -c "$dir" "$pane_creation_command"
 	else
@@ -150,7 +152,8 @@ new_pane() {
 	local window_name="$3"
 	local dir="$4"
 	local pane_index="$5"
-	if is_restoring_pane_contents; then
+	local pane_id="${session_name}:${window_number}.${pane_index}"
+	if is_restoring_pane_contents && pane_contents_file_exists "$pane_id"; then
 		local pane_creation_command="$(pane_creation_command "$session_name" "$window_number" "$pane_index")"
 		tmux split-window -t "${session_name}:${window_number}" -c "$dir" "$pane_creation_command"
 	else
diff --git a/scripts/save.sh b/scripts/save.sh
index b2a9d4f..fe84f1a 100755
--- a/scripts/save.sh
+++ b/scripts/save.sh
@@ -110,14 +110,36 @@ pane_full_command() {
 	$strategy_file "$pane_pid"
 }
 
+number_nonempty_lines_on_screen() {
+	local pane_id="$1"
+	tmux capture-pane -pJ -t "$pane_id" |
+		sed '/^$/d' |
+		wc -l |
+		sed 's/ //g'
+}
+
+# tests if there was any command output in the current pane
+pane_has_any_content() {
+	local pane_id="$1"
+	local history_size="$(tmux display -p -t "$pane_id" -F "#{history_size}")"
+	local cursor_y="$(tmux display -p -t "$pane_id" -F "#{cursor_y}")"
+	# doing "cheap" tests first
+	[ "$history_size" -gt 0 ] || # history has any content?
+		[ "$cursor_y" -gt 0 ] || # cursor not in first line?
+		[ "$(number_nonempty_lines_on_screen "$pane_id")" -gt 1 ]
+}
+
 capture_pane_contents() {
 	local pane_id="$1"
 	local start_line="-$2"
 	local pane_contents_area="$3"
-	if [ "$pane_contents_area" = "visible" ]; then
-		start_line="0"
+	if pane_has_any_content "$pane_id"; then
+		if [ "$pane_contents_area" = "visible" ]; then
+			start_line="0"
+		fi
+		# the printf hack below removes *trailing* empty lines
+		printf '%s\n' "$(tmux capture-pane -epJ -S "$start_line" -t "$pane_id")" > "$(pane_contents_file "$pane_id")"
 	fi
-	printf '%s\n' "$(tmux capture-pane -epJ -S "$start_line" -t "$pane_id")" > "$(pane_contents_file "$pane_id")"
 }
 
 save_shell_history() {