From 4ae2c646576cc4e9f91c730c80bf75fd5122e4b3 Mon Sep 17 00:00:00 2001
From: nicm <nicm>
Date: Mon, 30 May 2022 12:52:02 +0000
Subject: [PATCH] Better error reporting when applying custom layouts.

---
 cmd-select-layout.c |  7 ++++---
 layout-custom.c     | 23 +++++++++++++++++------
 2 files changed, 21 insertions(+), 9 deletions(-)

diff --git a/cmd-select-layout.c b/cmd-select-layout.c
index c857a0e1..6dfe2b6a 100644
--- a/cmd-select-layout.c
+++ b/cmd-select-layout.c
@@ -77,7 +77,7 @@ cmd_select_layout_exec(struct cmd *self, struct cmdq_item *item)
 	struct window		*w = wl->window;
 	struct window_pane	*wp = target->wp;
 	const char		*layoutname;
-	char			*oldlayout;
+	char			*oldlayout, *cause;
 	int			 next, previous, layout;
 
 	server_unzoom_window(w);
@@ -124,8 +124,9 @@ cmd_select_layout_exec(struct cmd *self, struct cmdq_item *item)
 	}
 
 	if (layoutname != NULL) {
-		if (layout_parse(w, layoutname) == -1) {
-			cmdq_error(item, "can't set layout: %s", layoutname);
+		if (layout_parse(w, layoutname, &cause) == -1) {
+			cmdq_error(item, "%s: %s", cause, layoutname);
+			free(cause);
 			goto error;
 		}
 		goto changed;
diff --git a/layout-custom.c b/layout-custom.c
index e7fb4253..932b30e7 100644
--- a/layout-custom.c
+++ b/layout-custom.c
@@ -154,7 +154,7 @@ layout_check(struct layout_cell *lc)
 
 /* Parse a layout string and arrange window as layout. */
 int
-layout_parse(struct window *w, const char *layout)
+layout_parse(struct window *w, const char *layout, char **cause)
 {
 	struct layout_cell	*lc, *lcchild;
 	struct window_pane	*wp;
@@ -165,22 +165,31 @@ layout_parse(struct window *w, const char *layout)
 	if (sscanf(layout, "%hx,", &csum) != 1)
 		return (-1);
 	layout += 5;
-	if (csum != layout_checksum(layout))
+	if (csum != layout_checksum(layout)) {
+		*cause = xstrdup("invalid layout");
 		return (-1);
+	}
 
 	/* Build the layout. */
 	lc = layout_construct(NULL, &layout);
-	if (lc == NULL)
+	if (lc == NULL) {
+		*cause = xstrdup("invalid layout");
 		return (-1);
-	if (*layout != '\0')
+	}
+	if (*layout != '\0') {
+		*cause = xstrdup("invalid layout");
 		goto fail;
+	}
 
 	/* Check this window will fit into the layout. */
 	for (;;) {
 		npanes = window_count_panes(w);
 		ncells = layout_count_cells(lc);
-		if (npanes > ncells)
+		if (npanes > ncells) {
+			xasprintf(cause, "have %u panes but need %u", npanes,
+			    ncells);
 			goto fail;
+		}
 		if (npanes == ncells)
 			break;
 
@@ -217,8 +226,10 @@ layout_parse(struct window *w, const char *layout)
 	}
 
 	/* Check the new layout. */
-	if (!layout_check(lc))
+	if (!layout_check(lc)) {
+		*cause = xstrdup("size mismatch after applying layout");
 		return (-1);
+	}
 
 	/* Resize to the layout size. */
 	window_resize(w, lc->sx, lc->sy, -1, -1);