Add a layout history which can be stepped through with select-layout -u

and -U commands (bound to 'u' and 'U' by default).

cmd-resize-pane.c

@@ -103,6 +103,7 @@ cmd_resize_pane_exec(struct cmd *self, struct cmd_ctx *ctx)
 		}
 	}
 
+	layout_list_add(wp->window);
 	if (args_has(self->args, 'L'))
 		layout_resize_pane(wp, LAYOUT_LEFTRIGHT, -adjust);
 	else if (args_has(self->args, 'R'))

cmd-select-layout.c

@@ -29,8 +29,8 @@ int	cmd_select_layout_exec(struct cmd *, struct cmd_ctx *);
 
 const struct cmd_entry cmd_select_layout_entry = {
 	"select-layout", "selectl",
-	"npt:", 0, 1,
-	"[-np] " CMD_TARGET_WINDOW_USAGE " [layout-name]",
+	"nprut:", 0, 1,
+	"[-npUu] " CMD_TARGET_WINDOW_USAGE " [layout-name]",
 	0,
 	cmd_select_layout_key_binding,
 	NULL,
@@ -76,6 +76,14 @@ cmd_select_layout_key_binding(struct cmd *self, int key)
 	case '5' | KEYC_ESCAPE:
 		self->args = args_create(1, "tiled");
 		break;
+	case 'u':
+		self->args = args_create(0);
+		args_set(self->args, 'u', NULL);
+		break;
+	case 'U':
+		self->args = args_create(0);
+		args_set(self->args, 'U', NULL);
+		break;
 	default:
 		self->args = args_create(0);
 		break;
@@ -87,11 +95,13 @@ cmd_select_layout_exec(struct cmd *self, struct cmd_ctx *ctx)
 {
 	struct args	*args = self->args;
 	struct winlink	*wl;
+	struct window	*w;
 	const char	*layoutname;
 	int		 next, previous, layout;
 
 	if ((wl = cmd_find_window(ctx, args_get(args, 't'), NULL)) == NULL)
 		return (-1);
+	w = wl->window;
 
 	next = self->entry == &cmd_next_layout_entry;
 	if (args_has(self->args, 'n'))
@@ -100,6 +110,21 @@ cmd_select_layout_exec(struct cmd *self, struct cmd_ctx *ctx)
 	if (args_has(self->args, 'p'))
 		previous = 1;
 
+	layout_list_add(w);
+	if (args_has(self->args, 'U')) {
+		if ((layoutname = layout_list_redo(w)) == NULL) {
+			ctx->error(ctx, "no more layout history");
+			return (-1);
+		}
+		goto set_layout;
+	} else if (args_has(self->args, 'u')) {
+		if ((layoutname = layout_list_undo(w)) == NULL) {
+			ctx->error(ctx, "no more layout history");
+			return (-1);
+		}
+		goto set_layout;
+	}
+
 	if (next || previous) {
 		if (next)
 			layout = layout_set_next(wl->window);
@@ -121,16 +146,16 @@ cmd_select_layout_exec(struct cmd *self, struct cmd_ctx *ctx)
 		return (0);
 	}
 
-	if (args->argc != 0) {
-		layoutname = args->argv[0];
-		if (layout_parse(wl->window, layoutname) == -1) {
-			ctx->error(ctx, "can't set layout: %s", layoutname);
-			return (-1);
-		}
-		server_redraw_window(wl->window);
-		ctx->info(ctx, "arranging in: %s", layoutname);
+	if (args->argc == 0)
 		return (0);
-	}
+	layoutname = args->argv[0];
 
+set_layout:
+	if (layout_parse(wl->window, layoutname) == -1) {
+		ctx->error(ctx, "can't set layout: %s", layoutname);
+		return (-1);
+	}
+	server_redraw_window(wl->window);
+	ctx->info(ctx, "arranging in: %s", layoutname);
 	return (0);
 }

key-bindings.c

@@ -130,6 +130,7 @@ key_bindings_init(void)
 		{ '?', 			  0, &cmd_list_keys_entry },
 		{ 'D',			  0, &cmd_choose_client_entry },
 		{ 'L',			  0, &cmd_switch_client_entry },
+		{ 'U',			  1, &cmd_select_layout_entry },
 		{ '[', 			  0, &cmd_copy_mode_entry },
 		{ '\'',			  0, &cmd_command_prompt_entry },
 		{ '\002', /* C-b */	  0, &cmd_send_prefix_entry },
@@ -148,6 +149,7 @@ key_bindings_init(void)
 		{ 'r', 			  0, &cmd_refresh_client_entry },
 		{ 's', 			  0, &cmd_choose_session_entry },
 		{ 't', 			  0, &cmd_clock_mode_entry },
+		{ 'u',			  1, &cmd_select_layout_entry },
 		{ 'w', 			  0, &cmd_choose_window_entry },
 		{ 'x', 			  0, &cmd_confirm_before_entry },
 		{ '{',			  0, &cmd_swap_pane_entry },

layout.c

@@ -19,6 +19,7 @@
 #include <sys/types.h>
 
 #include <stdlib.h>
+#include <string.h>
 
 #include "tmux.h"
 
@@ -745,3 +746,74 @@ layout_close_pane(struct window_pane *wp)
 	}
 	notify_window_layout_changed(wp->window);
 }
+
+/* Add layout to list. */
+void
+layout_list_add(struct window *w)
+{
+	struct last_layout	*ll, *ll_last;
+	char			*layout;
+	u_int			 limit;
+
+	layout = layout_dump(w);
+
+	ll_last = w->layout_list_last;
+	if (ll_last != NULL && strcmp(ll_last->layout, layout) == 0) {
+		free(layout);
+		return;
+	}
+
+	ll = xmalloc(sizeof *ll);
+	ll->layout = layout;
+	if (ll_last == NULL)
+		TAILQ_INSERT_TAIL(&w->layout_list, ll, entry);
+	else
+		TAILQ_INSERT_AFTER(&w->layout_list, ll_last, ll, entry);
+	w->layout_list_size++;
+	w->layout_list_last = ll;
+
+	limit = options_get_number(&w->options, "layout-history");
+	while (w->layout_list_size > limit) {
+		ll = TAILQ_LAST(&w->layout_list, last_layouts);
+		if (ll == w->layout_list_last)
+			ll = TAILQ_FIRST(&w->layout_list);
+
+		TAILQ_REMOVE(&w->layout_list, ll, entry);
+		w->layout_list_size--;
+
+		xfree(ll->layout);
+		xfree(ll);
+	}
+}
+
+/* Apply next layout from list. */
+const char *
+layout_list_redo(struct window *w)
+{
+	struct last_layout	*ll, *ll_last;
+
+	ll_last = w->layout_list_last;
+	if (ll_last == NULL)
+		return (NULL);
+	ll = TAILQ_NEXT(ll_last, entry);
+	if (ll == NULL)
+		return (NULL);
+	w->layout_list_last = ll;
+	return (ll->layout);
+}
+
+/* Apply previous layout from list. */
+const char *
+layout_list_undo(struct window *w)
+{
+	struct last_layout	*ll, *ll_last;
+
+	ll_last = w->layout_list_last;
+	if (ll_last == NULL)
+		return (NULL);
+	ll = TAILQ_PREV(ll_last, last_layouts, entry);
+	if (ll == NULL)
+		return (NULL);
+	w->layout_list_last = ll;
+	return (ll->layout);
+}

options-table.c

@@ -505,6 +505,13 @@ const struct options_table_entry window_options_table[] = {
 	  .default_num = 0
 	},
 
+	{ .name = "layout-history-limit",
+	  .type = OPTIONS_TABLE_NUMBER,
+	  .minimum = 1,
+	  .maximum = USHRT_MAX,
+	  .default_num = 20
+	},
+
 	{ .name = "main-pane-height",
 	  .type = OPTIONS_TABLE_NUMBER,
 	  .minimum = 1,

tmux.1

@@ -1451,7 +1451,7 @@ lower) with
 .Fl U
 or downward (numerically higher).
 .It Xo Ic select-layout
-.Op Fl np
+.Op Fl npUu
 .Op Fl t Ar target-window
 .Op Ar layout-name
 .Xc
@@ -1468,6 +1468,13 @@ are equivalent to the
 and
 .Ic previous-layout
 commands.
+.Pp
+.Fl U
+and
+.Fl u
+step forward and back through previous layouts, up to the maximum set by the
+.Ic layout-history-limit
+option.
 .It Xo Ic select-pane
 .Op Fl lDLRU
 .Op Fl t Ar target-pane
@@ -2509,6 +2516,13 @@ or
 .Ar height .
 A value of zero restores the default unlimited setting.
 .Pp
+.It Ic layout-history-limit Ar limit
+Set the number of previous layouts stored for recovery with
+.Ic select-layout
+.Fl U
+and
+.Fl u .
+.Pp
 .It Ic main-pane-height Ar height
 .It Ic main-pane-width Ar width
 Set the width or height of the main (left or top) pane in the

tmux.h

@@ -851,6 +851,13 @@ struct window_pane {
 TAILQ_HEAD(window_panes, window_pane);
 RB_HEAD(window_pane_tree, window_pane);
 
+/* Window last layout. */
+struct last_layout {
+	char	*layout;
+
+	TAILQ_ENTRY(last_layout) entry;
+};
+
 /* Window structure. */
 struct window {
 	u_int		 id;
@@ -864,6 +871,9 @@ struct window {
 
 	int		 lastlayout;
 	struct layout_cell *layout_root;
+	TAILQ_HEAD(last_layouts, last_layout) layout_list;
+	u_int		 layout_list_size;
+	struct last_layout *layout_list_last;
 
 	u_int		 sx;
 	u_int		 sy;
@@ -1998,7 +2008,8 @@ u_int		 layout_count_cells(struct layout_cell *);
 struct layout_cell *layout_create_cell(struct layout_cell *);
 void		 layout_free_cell(struct layout_cell *);
 void		 layout_print_cell(struct layout_cell *, const char *, u_int);
-void		 layout_destroy_cell(struct layout_cell *, struct layout_cell **);
+void		 layout_destroy_cell(
+		     struct layout_cell *, struct layout_cell **);
 void		 layout_set_size(
 		     struct layout_cell *, u_int, u_int, u_int, u_int);
 void		 layout_make_leaf(
@@ -2020,6 +2031,9 @@ void		 layout_assign_pane(struct layout_cell *, struct window_pane *);
 struct layout_cell *layout_split_pane(
 		     struct window_pane *, enum layout_type, int, int);
 void		 layout_close_pane(struct window_pane *);
+void		 layout_list_add(struct window *);
+const char	*layout_list_redo(struct window *);
+const char	*layout_list_undo(struct window *);
 
 /* layout-custom.c */
 char		*layout_dump(struct window *);

window.c

@@ -292,6 +292,7 @@ window_create1(u_int sx, u_int sy)
 
 	w->lastlayout = -1;
 	w->layout_root = NULL;
+	TAILQ_INIT(&w->layout_list);
 
 	w->sx = sx;
 	w->sy = sy;