Permit shortcut keys in buffer, client, tree modes to be configured with

a format; the default remains the line number. GitHub issue 2636.

9 files changed, 261 insertions, 54 deletions

diff --git a/cmd-choose-tree.c b/cmd-choose-tree.c
index a58469ac..81209ee3 100644
--- a/cmd-choose-tree.c
+++ b/cmd-choose-tree.c
@@ -30,9 +30,9 @@ const struct cmd_entry cmd_choose_tree_entry = {
 	.name = "choose-tree",
 	.alias = NULL,
 
-	.args = { "F:Gf:NO:rst:wZ", 0, 1 },
-	.usage = "[-GNrswZ] [-F format] [-f filter] [-O sort-order] "
-	         CMD_TARGET_PANE_USAGE " [template]",
+	.args = { "F:f:GK:NO:rst:wZ", 0, 1 },
+	.usage = "[-GNrswZ] [-F format] [-f filter] [-K key-format] "
+		 "[-O sort-order] " CMD_TARGET_PANE_USAGE " [template]",
 
 	.target = { 't', CMD_FIND_PANE, 0 },
 
@@ -44,9 +44,9 @@ const struct cmd_entry cmd_choose_client_entry = {
 	.name = "choose-client",
 	.alias = NULL,
 
-	.args = { "F:f:NO:rt:Z", 0, 1 },
-	.usage = "[-NrZ] [-F format] [-f filter] [-O sort-order] "
-	         CMD_TARGET_PANE_USAGE " [template]",
+	.args = { "F:f:K:NO:rt:Z", 0, 1 },
+	.usage = "[-NrZ] [-F format] [-f filter] [-K key-format] "
+		 "[-O sort-order] " CMD_TARGET_PANE_USAGE " [template]",
 
 	.target = { 't', CMD_FIND_PANE, 0 },
 
@@ -58,9 +58,9 @@ const struct cmd_entry cmd_choose_buffer_entry = {
 	.name = "choose-buffer",
 	.alias = NULL,
 
-	.args = { "F:f:NO:rt:Z", 0, 1 },
-	.usage = "[-NrZ] [-F format] [-f filter] [-O sort-order] "
-	         CMD_TARGET_PANE_USAGE " [template]",
+	.args = { "F:f:K:NO:rt:Z", 0, 1 },
+	.usage = "[-NrZ] [-F format] [-f filter] [-K key-format] "
+		 "[-O sort-order] " CMD_TARGET_PANE_USAGE " [template]",
 
 	.target = { 't', CMD_FIND_PANE, 0 },
 
diff --git a/format.c b/format.c
index 80e72cf0..3a1385b2 100644
--- a/format.c
+++ b/format.c
@@ -100,6 +100,7 @@ format_job_cmp(struct format_job *fj1, struct format_job *fj2)
 #define FORMAT_QUOTE_STYLE 0x2000
 #define FORMAT_WINDOW_NAME 0x4000
 #define FORMAT_SESSION_NAME 0x8000
+#define FORMAT_CHARACTER 0x10000
 
 /* Limit on recursion. */
 #define FORMAT_LOOP_LIMIT 10
@@ -3522,7 +3523,7 @@ format_build_modifiers(struct format_expand_state *es, const char **s,
 
 	/*
 	 * Modifiers are a ; separated list of the forms:
-	 *      l,m,C,b,d,n,t,w,q,E,T,S,W,P,<,>
+	 *      l,m,C,a,b,d,n,t,w,q,E,T,S,W,P,<,>
 	 *	=a
 	 *	=/a
 	 *      =/a/
@@ -3539,7 +3540,7 @@ format_build_modifiers(struct format_expand_state *es, const char **s,
 			cp++;
 
 		/* Check single character modifiers with no arguments. */
-		if (strchr("lbdnwETSWP<>", cp[0]) != NULL &&
+		if (strchr("labdnwETSWP<>", cp[0]) != NULL &&
 		    format_is_end(cp[1])) {
 			format_add_modifier(&list, count, cp, 1, NULL, 0);
 			cp++;
@@ -3956,7 +3957,7 @@ format_replace_expression(struct format_modifier *mexp,
 		mright = (long long)mright;
 	}
 	format_log(es, "expression left side is: %.*f", prec, mleft);
-	format_log(es, "expression right side is:  %.*f", prec, mright);
+	format_log(es, "expression right side is: %.*f", prec, mright);
 
 	switch (operator) {
 	case ADD:
@@ -4016,10 +4017,10 @@ format_replace(struct format_expand_state *es, const char *key, size_t keylen,
 {
 	struct format_tree		 *ft = es->ft;
 	struct window_pane		 *wp = ft->wp;
-	const char			 *errptr, *copy, *cp, *marker = NULL;
+	const char			 *errstr, *copy, *cp, *marker = NULL;
 	const char			 *time_format = NULL;
 	char				 *copy0, *condition, *found, *new;
-	char				 *value, *left, *right;
+	char				 *value, *left, *right, c;
 	size_t				  valuelen;
 	int				  modifiers = 0, limit = 0, width = 0;
 	int				  j;
@@ -4063,8 +4064,8 @@ format_replace(struct format_expand_state *es, const char *key, size_t keylen,
 				if (fm->argc < 1)
 					break;
 				limit = strtonum(fm->argv[0], INT_MIN, INT_MAX,
-				    &errptr);
-				if (errptr != NULL)
+				    &errstr);
+				if (errstr != NULL)
 					limit = 0;
 				if (fm->argc >= 2 && fm->argv[1] != NULL)
 					marker = fm->argv[1];
@@ -4073,8 +4074,8 @@ format_replace(struct format_expand_state *es, const char *key, size_t keylen,
 				if (fm->argc < 1)
 					break;
 				width = strtonum(fm->argv[0], INT_MIN, INT_MAX,
-				    &errptr);
-				if (errptr != NULL)
+				    &errstr);
+				if (errstr != NULL)
 					width = 0;
 				break;
 			case 'w':
@@ -4088,6 +4089,9 @@ format_replace(struct format_expand_state *es, const char *key, size_t keylen,
 			case 'l':
 				modifiers |= FORMAT_LITERAL;
 				break;
+			case 'a':
+				modifiers |= FORMAT_CHARACTER;
+				break;
 			case 'b':
 				modifiers |= FORMAT_BASENAME;
 				break;
@@ -4154,6 +4158,18 @@ format_replace(struct format_expand_state *es, const char *key, size_t keylen,
 		goto done;
 	}
 
+	/* Is this a character? */
+	if (modifiers & FORMAT_CHARACTER) {
+		new = format_expand1(es, copy);
+		c = strtonum(new, 32, 126, &errstr);
+		if (errstr != NULL)
+			value = xstrdup("");
+		else
+			xasprintf(&value, "%c", c);
+		free (new);
+		goto done;
+	}
+
 	/* Is this a loop, comparison or condition? */
 	if (modifiers & FORMAT_SESSIONS) {
 		value = format_loop_sessions(es, copy);
diff --git a/mode-tree.c b/mode-tree.c
index a47c0c06..c0f85026 100644
--- a/mode-tree.c
+++ b/mode-tree.c
@@ -46,6 +46,7 @@ struct mode_tree_data {
 	mode_tree_search_cb       searchcb;
 	mode_tree_menu_cb         menucb;
 	mode_tree_height_cb       heightcb;
+	mode_tree_key_cb	  keycb;
 
 	struct mode_tree_list	  children;
 	struct mode_tree_list	  saved;
@@ -74,6 +75,10 @@ struct mode_tree_item {
 	void				*itemdata;
 	u_int				 line;
 
+	key_code			 key;
+	const char			*keystr;
+	size_t				 keylen;
+
 	uint64_t			 tag;
 	const char			*name;
 	const char			*text;
@@ -135,6 +140,7 @@ mode_tree_free_item(struct mode_tree_item *mti)
 
 	free((void *)mti->name);
 	free((void *)mti->text);
+	free((void *)mti->keystr);
 
 	free(mti);
 }
@@ -193,6 +199,26 @@ mode_tree_build_lines(struct mode_tree_data *mtd,
 			flat = 0;
 		if (mti->expanded)
 			mode_tree_build_lines(mtd, &mti->children, depth + 1);
+
+		if (mtd->keycb != NULL) {
+			mti->key = mtd->keycb(mtd->modedata, mti->itemdata,
+			    mti->line);
+			if (mti->key == KEYC_UNKNOWN)
+				mti->key = KEYC_NONE;
+		} else if (mti->line < 10)
+			mti->key = '0' + mti->line;
+		else if (mti->line < 36)
+			mti->key = KEYC_META|('a' + mti->line - 10);
+		else
+			mti->key = KEYC_NONE;
+		if (mti->key != KEYC_NONE) {
+			mti->keystr = xstrdup(key_string_lookup_key(mti->key,
+			    0));
+			mti->keylen = strlen(mti->keystr);
+		} else {
+			mti->keystr = NULL;
+			mti->keylen = 0;
+		}
 	}
 	TAILQ_FOREACH(mti, mtl, entry) {
 		for (i = 0; i < mtd->line_size; i++) {
@@ -363,7 +389,7 @@ struct mode_tree_data *
 mode_tree_start(struct window_pane *wp, struct args *args,
     mode_tree_build_cb buildcb, mode_tree_draw_cb drawcb,
     mode_tree_search_cb searchcb, mode_tree_menu_cb menucb,
-    mode_tree_height_cb heightcb, void *modedata,
+    mode_tree_height_cb heightcb, mode_tree_key_cb keycb, void *modedata,
     const struct menu_item *menu, const char **sort_list, u_int sort_size,
     struct screen **s)
 {
@@ -402,6 +428,7 @@ mode_tree_start(struct window_pane *wp, struct args *args,
 	mtd->searchcb = searchcb;
 	mtd->menucb = menucb;
 	mtd->heightcb = heightcb;
+	mtd->keycb = keycb;
 
 	TAILQ_INIT(&mtd->children);
 
@@ -596,10 +623,10 @@ mode_tree_draw(struct mode_tree_data *mtd)
 	struct screen_write_ctx	 ctx;
 	struct grid_cell	 gc0, gc;
 	u_int			 w, h, i, j, sy, box_x, box_y, width;
-	char			*text, *start, key[7];
+	char			*text, *start, *key;
 	const char		*tag, *symbol;
 	size_t			 size, n;
-	int			 keylen;
+	int			 keylen, pad;
 
 	if (mtd->line_size == 0)
 		return;
@@ -614,28 +641,30 @@ mode_tree_draw(struct mode_tree_data *mtd)
 	screen_write_start(&ctx, s);
 	screen_write_clearscreen(&ctx, 8);
 
-	if (mtd->line_size > 10)
-		keylen = 6;
-	else
-		keylen = 4;
+	keylen = 0;
+	for (i = 0; i < mtd->line_size; i++) {
+		mti = mtd->line_list[i].item;
+		if (mti->key == KEYC_NONE)
+			continue;
+		if ((int)mti->keylen + 3 > keylen)
+			keylen = mti->keylen + 3;
+	}
 
 	for (i = 0; i < mtd->line_size; i++) {
 		if (i < mtd->offset)
 			continue;
 		if (i > mtd->offset + h - 1)
 			break;
-
 		line = &mtd->line_list[i];
 		mti = line->item;
 
 		screen_write_cursormove(&ctx, 0, i - mtd->offset, 0);
 
-		if (i < 10)
-			snprintf(key, sizeof key, "(%c)  ", '0' + i);
-		else if (i < 36)
-			snprintf(key, sizeof key, "(M-%c)", 'a' + (i - 10));
+		pad = keylen - 2 - mti->keylen;
+		if (mti->key != KEYC_NONE)
+			xasprintf(&key, "(%s)%*s", mti->keystr, pad, "");
 		else
-			*key = '\0';
+			key = xstrdup("");
 
 		if (line->flat)
 			symbol = "";
@@ -698,6 +727,7 @@ mode_tree_draw(struct mode_tree_data *mtd)
 			}
 		}
 		free(text);
+		free(key);
 
 		if (mti->tagged) {
 			gc.attr ^= GRID_ATTR_BRIGHT;
@@ -951,7 +981,6 @@ mode_tree_key(struct mode_tree_data *mtd, struct client *c, key_code *key,
 	struct mode_tree_item	*current, *parent, *mti;
 	u_int			 i, x, y;
 	int			 choice;
-	key_code		 tmp;
 
 	if (KEYC_IS_MOUSE(*key) && m != NULL) {
 		if (cmd_mouse_at(mtd->wp, m, &x, &y, 0) != 0) {
@@ -993,12 +1022,11 @@ mode_tree_key(struct mode_tree_data *mtd, struct client *c, key_code *key,
 	current = line->item;
 
 	choice = -1;
-	if (*key >= '0' && *key <= '9')
-		choice = (*key) - '0';
-	else if (((*key) & KEYC_MASK_MODIFIERS) == KEYC_META) {
-		tmp = (*key) & KEYC_MASK_KEY;
-		if (tmp >= 'a' && tmp <= 'z')
-			choice = 10 + (tmp - 'a');
+	for (i = 0; i < mtd->line_size; i++) {
+		if (*key == mtd->line_list[i].item->key) {
+			choice = i;
+			break;
+		}
 	}
 	if (choice != -1) {
 		if ((u_int)choice > mtd->line_size - 1) {
diff --git a/tmux.1 b/tmux.1
index 00b5cd84..74cb5f00 100644
--- a/tmux.1
+++ b/tmux.1
@@ -1985,12 +1985,17 @@ The default is to capture only the visible contents of the pane.
 .Op Fl NrZ
 .Op Fl F Ar format
 .Op Fl f Ar filter
+.Op Fl K Ar key-format
 .Op Fl O Ar sort-order
 .Op Fl t Ar target-pane
 .Op Ar template
 .Xc
 Put a pane into client mode, allowing a client to be selected interactively from
 a list.
+Each client is shown on one line.
+A shortcut key is shown on the left in brackets allowing for immediate choice,
+or the list may be navigated and an item chosen or otherwise manipulated using
+the keys below.
 .Fl Z
 zooms the pane.
 The following keys may be used in client mode:
@@ -2040,7 +2045,9 @@ specifies an initial filter: the filter is a format - if it evaluates to zero,
 the item in the list is not shown, otherwise it is shown.
 If a filter would lead to an empty list, it is ignored.
 .Fl F
-specifies the format for each item in the list.
+specifies the format for each item in the list and
+.Fl K
+a format for each shortcut key; both are evaluated once for each line.
 .Fl N
 starts without the preview.
 This command works only if at least one client is attached.
@@ -2049,12 +2056,17 @@ This command works only if at least one client is attached.
 .Op Fl GNrswZ
 .Op Fl F Ar format
 .Op Fl f Ar filter
+.Op Fl K Ar key-format
 .Op Fl O Ar sort-order
 .Op Fl t Ar target-pane
 .Op Ar template
 .Xc
 Put a pane into tree mode, where a session, window or pane may be chosen
-interactively from a list.
+interactively from a tree.
+Each session, window or pane is shown on one line.
+A shortcut key is shown on the left in brackets allowing for immediate choice,
+or the tree may be navigated and an item chosen or otherwise manipulated using
+the keys below.
 .Fl s
 starts with sessions collapsed and
 .Fl w
@@ -2113,7 +2125,9 @@ specifies an initial filter: the filter is a format - if it evaluates to zero,
 the item in the list is not shown, otherwise it is shown.
 If a filter would lead to an empty list, it is ignored.
 .Fl F
-specifies the format for each item in the tree.
+specifies the format for each item in the tree and
+.Fl K
+a format for each shortcut key; both are evaluated once for each line.
 .Fl N
 starts without the preview.
 .Fl G
@@ -4663,6 +4677,11 @@ For example,
 multiplies 5.5 by 3 for a result with four decimal places and
 .Ql #{e|%%:7,3}
 returns the modulus of 7 and 3.
+.Ql a
+replaces a numeric argument by its ASCII equivalent, so
+.Ql #{a:98}
+results in
+.Ql b .
 .Pp
 A limit may be placed on the length of the resultant string by prefixing it
 by an
@@ -5681,12 +5700,17 @@ The buffer commands are as follows:
 .Op Fl NZr
 .Op Fl F Ar format
 .Op Fl f Ar filter
+.Op Fl K Ar key-format
 .Op Fl O Ar sort-order
 .Op Fl t Ar target-pane
 .Op Ar template
 .Xc
 Put a pane into buffer mode, where a buffer may be chosen interactively from
 a list.
+Each buffer is shown on one line.
+A shortcut key is shown on the left in brackets allowing for immediate choice,
+or the list may be navigated and an item chosen or otherwise manipulated using
+the keys below.
 .Fl Z
 zooms the pane.
 The following keys may be used in buffer mode:
@@ -5734,7 +5758,9 @@ specifies an initial filter: the filter is a format - if it evaluates to zero,
 the item in the list is not shown, otherwise it is shown.
 If a filter would lead to an empty list, it is ignored.
 .Fl F
-specifies the format for each item in the list.
+specifies the format for each item in the list and
+.Fl K
+a format for each shortcut key; both are evaluated once for each line.
 .Fl N
 starts without the preview.
 This command works only if at least one client is attached.
diff --git a/tmux.h b/tmux.h
index 0c7636f8..9160ef92 100644
--- a/tmux.h
+++ b/tmux.h
@@ -2855,6 +2855,7 @@ typedef void (*mode_tree_draw_cb)(void *, void *, struct screen_write_ctx *,
 typedef int (*mode_tree_search_cb)(void *, void *, const char *);
 typedef void (*mode_tree_menu_cb)(void *, struct client *, key_code);
 typedef u_int (*mode_tree_height_cb)(void *, u_int);
+typedef key_code (*mode_tree_key_cb)(void *, void *, u_int);
 typedef void (*mode_tree_each_cb)(void *, void *, struct client *, key_code);
 u_int	 mode_tree_count_tagged(struct mode_tree_data *);
 void	*mode_tree_get_current(struct mode_tree_data *);
@@ -2869,7 +2870,7 @@ void	 mode_tree_up(struct mode_tree_data *, int);
 void	 mode_tree_down(struct mode_tree_data *, int);
 struct mode_tree_data *mode_tree_start(struct window_pane *, struct args *,
 	     mode_tree_build_cb, mode_tree_draw_cb, mode_tree_search_cb,
-	     mode_tree_menu_cb, mode_tree_height_cb, void *,
+	     mode_tree_menu_cb, mode_tree_height_cb, mode_tree_key_cb, void *,
 	     const struct menu_item *, const char **, u_int, struct screen **);
 void	 mode_tree_zoom(struct mode_tree_data *, struct args *);
 void	 mode_tree_build(struct mode_tree_data *);
diff --git a/window-buffer.c b/window-buffer.c
index 4599cbc5..5e4dd699 100644
--- a/window-buffer.c
+++ b/window-buffer.c
@@ -41,6 +41,17 @@ static void		 window_buffer_key(struct window_mode_entry *,
 #define WINDOW_BUFFER_DEFAULT_FORMAT \
 	"#{t/p:buffer_created}: #{buffer_sample}"
 
+#define WINDOW_BUFFER_DEFAULT_KEY_FORMAT \
+	"#{?#{e|<:#{line},10}," \
+		"#{line}" \
+	"," \
+		"#{?#{e|<:#{line},36},"	\
+	        	"M-#{a:#{e|+:97,#{e|-:#{line},10}}}" \
+		"," \
+	        	"" \
+		"}" \
+	"}"
+
 static const struct menu_item window_buffer_menu_items[] = {
 	{ "Paste", 'p', NULL },
 	{ "Paste Tagged", 'P', NULL },
@@ -93,6 +104,7 @@ struct window_buffer_modedata {
 	struct mode_tree_data		 *data;
 	char				 *command;
 	char				 *format;
+	char				 *key_format;
 
 	struct window_buffer_itemdata	**item_list;
 	u_int				  item_size;
@@ -232,7 +244,8 @@ window_buffer_draw(__unused void *modedata, void *itemdata,
 		while (end != pdata + psize && *end != '\n')
 			end++;
 		buf = xreallocarray(buf, 4, end - start + 1);
-		utf8_strvis(buf, start, end - start, VIS_OCTAL|VIS_CSTYLE|VIS_TAB);
+		utf8_strvis(buf, start, end - start,
+		    VIS_OCTAL|VIS_CSTYLE|VIS_TAB);
 		if (*buf != '\0') {
 			screen_write_cursormove(ctx, cx, cy + i, 0);
 			screen_write_nputs(ctx, sx, &grid_default_cell, "%s",
@@ -275,6 +288,41 @@ window_buffer_menu(void *modedata, struct client *c, key_code key)
 	window_buffer_key(wme, c, NULL, NULL, key, NULL);
 }
 
+static key_code
+window_buffer_get_key(void *modedata, void *itemdata, u_int line)
+{
+	struct window_buffer_modedata	*data = modedata;
+	struct window_buffer_itemdata	*item = itemdata;
+	struct format_tree		*ft;
+	struct session			*s;
+	struct winlink			*wl;
+	struct window_pane		*wp;
+	struct paste_buffer		*pb;
+	char				*expanded;
+	key_code			 key;
+
+	if (cmd_find_valid_state(&data->fs)) {
+		s = data->fs.s;
+		wl = data->fs.wl;
+		wp = data->fs.wp;
+	}
+	pb = paste_get_name(item->name);
+	if (pb == NULL)
+		return KEYC_NONE;
+
+	ft = format_create(NULL, NULL, FORMAT_NONE, 0);
+	format_defaults(ft, NULL, NULL, 0, NULL);
+	format_defaults(ft, NULL, s, wl, wp);
+	format_defaults_paste_buffer(ft, pb);
+	format_add(ft, "line", "%u", line);
+
+	expanded = format_expand(ft, data->key_format);
+	key = key_string_lookup_string(expanded);
+	free(expanded);
+	format_free(ft);
+	return key;
+}
+
 static struct screen *
 window_buffer_init(struct window_mode_entry *wme, struct cmd_find_state *fs,
     struct args *args)
@@ -291,6 +339,10 @@ window_buffer_init(struct window_mode_entry *wme, struct cmd_find_state *fs,
 		data->format = xstrdup(WINDOW_BUFFER_DEFAULT_FORMAT);
 	else
 		data->format = xstrdup(args_get(args, 'F'));
+	if (args == NULL || !args_has(args, 'K'))
+		data->key_format = xstrdup(WINDOW_BUFFER_DEFAULT_KEY_FORMAT);
+	else
+		data->key_format = xstrdup(args_get(args, 'K'));
 	if (args == NULL || args->argc == 0)
 		data->command = xstrdup(WINDOW_BUFFER_DEFAULT_COMMAND);
 	else
@@ -298,8 +350,8 @@ window_buffer_init(struct window_mode_entry *wme, struct cmd_find_state *fs,
 
 	data->data = mode_tree_start(wp, args, window_buffer_build,
 	    window_buffer_draw, window_buffer_search, window_buffer_menu, NULL,
-	    data, window_buffer_menu_items, window_buffer_sort_list,
-	    nitems(window_buffer_sort_list), &s);
+	    window_buffer_get_key, data, window_buffer_menu_items,
+	    window_buffer_sort_list, nitems(window_buffer_sort_list), &s);
 	mode_tree_zoom(data->data, args);
 
 	mode_tree_build(data->data);
@@ -324,6 +376,7 @@ window_buffer_free(struct window_mode_entry *wme)
 	free(data->item_list);
 
 	free(data->format);
+	free(data->key_format);
 	free(data->command);
 
 	free(data);
diff --git a/window-client.c b/window-client.c
index ec3c646a..db7c6dcc 100644
--- a/window-client.c
+++ b/window-client.c
@@ -40,6 +40,17 @@ static void		 window_client_key(struct window_mode_entry *,
 #define WINDOW_CLIENT_DEFAULT_FORMAT \
 	"#{t/p:client_activity}: session #{session_name}"
 
+#define WINDOW_CLIENT_DEFAULT_KEY_FORMAT \
+	"#{?#{e|<:#{line},10}," \
+		"#{line}" \
+	"," \
+		"#{?#{e|<:#{line},36},"	\
+	        	"M-#{a:#{e|+:97,#{e|-:#{line},10}}}" \
+		"," \
+	        	"" \
+		"}" \
+	"}"
+
 static const struct menu_item window_client_menu_items[] = {
 	{ "Detach", 'd', NULL },
 	{ "Detach Tagged", 'D', NULL },
@@ -87,6 +98,7 @@ struct window_client_modedata {
 
 	struct mode_tree_data		 *data;
 	char				 *format;
+	char				 *key_format;
 	char				 *command;
 
 	struct window_client_itemdata	**item_list;
@@ -252,6 +264,26 @@ window_client_menu(void *modedata, struct client *c, key_code key)
 	window_client_key(wme, c, NULL, NULL, key, NULL);
 }
 
+static key_code
+window_client_get_key(void *modedata, void *itemdata, u_int line)
+{
+	struct window_client_modedata	*data = modedata;
+	struct window_client_itemdata	*item = itemdata;
+	struct format_tree		*ft;
+	char				*expanded;
+	key_code			 key;
+
+	ft = format_create(NULL, NULL, FORMAT_NONE, 0);
+	format_defaults(ft, item->c, NULL, 0, NULL);
+	format_add(ft, "line", "%u", line);
+
+	expanded = format_expand(ft, data->key_format);
+	key = key_string_lookup_string(expanded);
+	free(expanded);
+	format_free(ft);
+	return key;
+}
+
 static struct screen *
 window_client_init(struct window_mode_entry *wme,
     __unused struct cmd_find_state *fs, struct args *args)
@@ -267,15 +299,19 @@ window_client_init(struct window_mode_entry *wme,
 		data->format = xstrdup(WINDOW_CLIENT_DEFAULT_FORMAT);
 	else
 		data->format = xstrdup(args_get(args, 'F'));
+	if (args == NULL || !args_has(args, 'K'))
+		data->key_format = xstrdup(WINDOW_CLIENT_DEFAULT_KEY_FORMAT);
+	else
+		data->key_format = xstrdup(args_get(args, 'K'));
 	if (args == NULL || args->argc == 0)
 		data->command = xstrdup(WINDOW_CLIENT_DEFAULT_COMMAND);
 	else
 		data->command = xstrdup(args->argv[0]);
 
 	data->data = mode_tree_start(wp, args, window_client_build,
-	    window_client_draw, NULL, window_client_menu, NULL, data,
-	    window_client_menu_items, window_client_sort_list,
-	    nitems(window_client_sort_list), &s);
+	    window_client_draw, NULL, window_client_menu, NULL,
+	    window_client_get_key, data, window_client_menu_items,
+	    window_client_sort_list, nitems(window_client_sort_list), &s);
 	mode_tree_zoom(data->data, args);
 
 	mode_tree_build(data->data);
@@ -300,6 +336,7 @@ window_client_free(struct window_mode_entry *wme)
 	free(data->item_list);
 
 	free(data->format);
+	free(data->key_format);
 	free(data->command);
 
 	free(data);
diff --git a/window-customize.c b/window-customize.c
index a1f191b5..fce002fd 100644
--- a/window-customize.c
+++ b/window-customize.c
@@ -890,8 +890,8 @@ window_customize_init(struct window_mode_entry *wme, struct cmd_find_state *fs,
 
 	data->data = mode_tree_start(wp, args, window_customize_build,
 	    window_customize_draw, NULL, window_customize_menu,
-	    window_customize_height, data, window_customize_menu_items, NULL, 0,
-	    &s);
+	    window_customize_height, NULL, data, window_customize_menu_items,
+	    NULL, 0, &s);
 	mode_tree_zoom(data->data, args);
 
 	mode_tree_build(data->data);
diff --git a/window-tree.c b/window-tree.c
index 1498b337..881896e7 100644
--- a/window-tree.c
+++ b/window-tree.c
@@ -56,6 +56,17 @@ static void		 window_tree_key(struct window_mode_entry *,
 		"}" \
 	"}"
 
+#define WINDOW_TREE_DEFAULT_KEY_FORMAT \
+	"#{?#{e|<:#{line},10}," \
+		"#{line}" \
+	"," \
+		"#{?#{e|<:#{line},36},"	\
+	        	"M-#{a:#{e|+:97,#{e|-:#{line},10}}}" \
+		"," \
+	        	"" \
+		"}" \
+	"}"
+
 static const struct menu_item window_tree_menu_items[] = {
 	{ "Select", '\r', NULL },
 	{ "Expand", KEYC_RIGHT, NULL },
@@ -117,6 +128,7 @@ struct window_tree_modedata {
 
 	struct mode_tree_data		 *data;
 	char				 *format;
+	char				 *key_format;
 	char				 *command;
 	int				  squash_groups;
 
@@ -856,6 +868,35 @@ window_tree_menu(void *modedata, struct client *c, key_code key)
 	window_tree_key(wme, c, NULL, NULL, key, NULL);
 }
 
+static key_code
+window_tree_get_key(void *modedata, void *itemdata, u_int line)
+{
+	struct window_tree_modedata	*data = modedata;
+	struct window_tree_itemdata	*item = itemdata;
+	struct format_tree		*ft;
+	struct session			*s;
+	struct winlink			*wl;
+	struct window_pane		*wp;
+	char				*expanded;
+	key_code			 key;
+
+	ft = format_create(NULL, NULL, FORMAT_NONE, 0);
+	window_tree_pull_item(item, &s, &wl, &wp);
+	if (item->type == WINDOW_TREE_SESSION)
+		format_defaults(ft, NULL, s, NULL, NULL);
+	else if (item->type == WINDOW_TREE_WINDOW)
+		format_defaults(ft, NULL, s, wl, NULL);
+	else
+		format_defaults(ft, NULL, s, wl, wp);
+	format_add(ft, "line", "%u", line);
+
+	expanded = format_expand(ft, data->key_format);
+	key = key_string_lookup_string(expanded);
+	free(expanded);
+	format_free(ft);
+	return key;
+}
+
 static struct screen *
 window_tree_init(struct window_mode_entry *wme, struct cmd_find_state *fs,
     struct args *args)
@@ -880,6 +921,10 @@ window_tree_init(struct window_mode_entry *wme, struct cmd_find_state *fs,
 		data->format = xstrdup(WINDOW_TREE_DEFAULT_FORMAT);
 	else
 		data->format = xstrdup(args_get(args, 'F'));
+	if (args == NULL || !args_has(args, 'K'))
+		data->key_format = xstrdup(WINDOW_TREE_DEFAULT_KEY_FORMAT);
+	else
+		data->key_format = xstrdup(args_get(args, 'K'));
 	if (args == NULL || args->argc == 0)
 		data->command = xstrdup(WINDOW_TREE_DEFAULT_COMMAND);
 	else
@@ -887,9 +932,9 @@ window_tree_init(struct window_mode_entry *wme, struct cmd_find_state *fs,
 	data->squash_groups = !args_has(args, 'G');
 
 	data->data = mode_tree_start(wp, args, window_tree_build,
-	    window_tree_draw, window_tree_search, window_tree_menu, NULL, data,
-	    window_tree_menu_items, window_tree_sort_list,
-	    nitems(window_tree_sort_list), &s);
+	    window_tree_draw, window_tree_search, window_tree_menu, NULL,
+	    window_tree_get_key, data, window_tree_menu_items,
+	    window_tree_sort_list, nitems(window_tree_sort_list), &s);
 	mode_tree_zoom(data->data, args);
 
 	mode_tree_build(data->data);
@@ -913,6 +958,7 @@ window_tree_destroy(struct window_tree_modedata *data)
 	free(data->item_list);
 
 	free(data->format);
+	free(data->key_format);
 	free(data->command);
 
 	free(data);