Add a new option, mouse-resize-pane. When on, panes may be resized by

dragging their borders. From hsim at gmx.li.

layout.c

@@ -485,6 +485,53 @@ layout_resize_pane(struct window_pane *wp, enum layout_type type, int change)
 	layout_fix_panes(wp->window, wp->window->sx, wp->window->sy);
 }
 
+void
+layout_resize_pane_mouse(struct client *c, struct mouse_event *mouse)
+{
+	struct window		*w;
+	struct window_pane	*wp;
+	int		      	 pane_border;
+
+	w = c->session->curw->window;
+
+	pane_border = 0;
+	if ((c->last_mouse.b & MOUSE_BUTTON) != MOUSE_UP &&
+		(c->last_mouse.b & MOUSE_RESIZE_PANE)) {
+		TAILQ_FOREACH(wp, &w->panes, entry) {
+			if (wp->xoff + wp->sx == c->last_mouse.x &&
+				wp->yoff <= 1 + c->last_mouse.y &&
+				wp->yoff + wp->sy >= c->last_mouse.y) {
+				layout_resize_pane(wp, LAYOUT_LEFTRIGHT,
+								   mouse->x - c->last_mouse.x);
+				pane_border = 1;
+			}
+			if (wp->yoff + wp->sy == c->last_mouse.y &&
+				wp->xoff <= 1 + c->last_mouse.x &&
+				wp->xoff + wp->sx >= c->last_mouse.x) {
+				layout_resize_pane(wp, LAYOUT_TOPBOTTOM,
+								   mouse->y - c->last_mouse.y);
+				pane_border = 1;
+			}
+		}
+		if (pane_border)
+			server_redraw_window(w);
+	} else if (mouse->b != MOUSE_UP &&
+			   mouse->b == (mouse->b & MOUSE_BUTTON)) {
+		TAILQ_FOREACH(wp, &w->panes, entry) {
+			if ((wp->xoff + wp->sx == mouse->x &&
+				 wp->yoff <= 1 + mouse->y &&
+				 wp->yoff + wp->sy >= mouse->y) ||
+				(wp->yoff + wp->sy == mouse->y &&
+				 wp->xoff <= 1 + mouse->x &&
+				 wp->xoff + wp->sx >= mouse->x)) {
+				pane_border = 1;
+			}
+		}
+	}
+	if (pane_border)
+		mouse->b |= MOUSE_RESIZE_PANE;
+}
+
 int
 layout_resize_pane_grow(
     struct layout_cell *lc, enum layout_type type, int needed)

options-table.c

@@ -193,6 +193,11 @@ const struct options_table_entry session_options_table[] = {
 	  .default_num = 20
 	},
 
+	{ .name = "mouse-resize-pane",
+	  .type = OPTIONS_TABLE_FLAG,
+	  .default_num = 0
+	},
+
 	{ .name = "mouse-select-pane",
 	  .type = OPTIONS_TABLE_FLAG,
 	  .default_num = 0

server-client.c

@@ -89,6 +89,9 @@ server_client_create(int fd)
 	c->prompt_buffer = NULL;
 	c->prompt_index = 0;
 
+	c->last_mouse.b = MOUSE_UP;
+	c->last_mouse.x = c->last_mouse.y = -1;
+
 	evtimer_set(&c->repeat_timer, server_client_repeat_timer, c);
 
 	for (i = 0; i < ARRAY_LENGTH(&clients); i++) {
@@ -344,6 +347,9 @@ server_client_handle_key(int key, struct mouse_event *mouse, void *data)
 				return;
 			}
 		}
+		if (options_get_number(oo, "mouse-resize-pane"))
+			layout_resize_pane_mouse(c, mouse);
+		memcpy(&c->last_mouse, mouse, sizeof c->last_mouse);
 		window_pane_mouse(wp, c->session, mouse);
 		return;
 	}
@@ -475,15 +481,25 @@ server_client_reset_state(struct client *c)
 	else
 		tty_cursor(&c->tty, wp->xoff + s->cx, wp->yoff + s->cy);
 
+	/*
+	 * Resizing panes with the mouse requires at least button mode to give
+	 * a smooth appearance.
+	 */
+	mode = s->mode;
+	if ((c->last_mouse.b & MOUSE_RESIZE_PANE) &&
+	    !(mode & (MODE_MOUSE_BUTTON|MODE_MOUSE_ANY)))
+		mode |= MODE_MOUSE_BUTTON;
+
 	/*
 	 * Any mode will do for mouse-select-pane, but set standard mode if
 	 * none.
 	 */
-	mode = s->mode;
 	if ((mode & ALL_MOUSE_MODES) == 0) {
 		if (TAILQ_NEXT(TAILQ_FIRST(&w->panes), entry) != NULL &&
 		    options_get_number(oo, "mouse-select-pane"))
 			mode |= MODE_MOUSE_STANDARD;
+		else if (options_get_number(oo, "mouse-resize-pane"))
+			mode |= MODE_MOUSE_STANDARD;
 		else if (options_get_number(oo, "mouse-select-window"))
 			mode |= MODE_MOUSE_STANDARD;
 		else if (options_get_number(wo, "mode-mouse"))

tmux.1

@@ -1888,6 +1888,12 @@ Set status line message foreground colour.
 Set the number of error or information messages to save in the message log for
 each client.
 The default is 20.
+.It Xo Ic mouse-resize-pane
+.Op Ic on | off
+.Xc
+If on,
+.Nm
+captures the mouse and allows panes to be resized by dragging on their borders.
 .It Xo Ic mouse-select-pane
 .Op Ic on | off
 .Xc

tmux.h

@@ -1086,6 +1086,7 @@ struct mouse_event {
 #define MOUSE_BUTTON 3
 #define MOUSE_DRAG 32
 #define MOUSE_45 64
+#define MOUSE_RESIZE_PANE 128 /* marker for resizing */
 	u_int	x;
 	u_int	y;
 };
@@ -1177,6 +1178,8 @@ struct client {
 	struct session	*session;
 	struct session	*last_session;
 
+	struct mouse_event last_mouse;
+
 	int		 references;
 };
 ARRAY_DECL(clients, struct client *);
@@ -1925,6 +1928,8 @@ void		 layout_free(struct window *);
 void		 layout_resize(struct window *, u_int, u_int);
 void		 layout_resize_pane(
 		     struct window_pane *, enum layout_type, int);
+void		 layout_resize_pane_mouse(
+		     struct client *c, struct mouse_event *mouse);
 void		 layout_assign_pane(struct layout_cell *, struct window_pane *);
 struct layout_cell *layout_split_pane(
 		     struct window_pane *, enum layout_type, int);