tree/load_layout: validate window_type literals strictly

Anchored ^name$ and bare names are accepted; everything else,
including regex alternation, returns a clear error instead of
silently falling through to ATOM_LAST.

Author: codegax

sway/sway.5.scd

@@ -426,7 +426,13 @@ runtime.
 	*class*, *instance*, *title*, *window_role*, and *window_type* keys
 	(which target xwayland views), each *swallows* entry may include
 	*app_id* to match Wayland views. The *machine* key is logged and
-	ignored. All values are PCRE2 regex strings.
+	ignored. *class*, *instance*, *title*, *window_role* and *app_id*
+	are PCRE2 regex strings. *window_type* must be a literal atom name
+	(*normal*, *dialog*, *utility*, *toolbar*, *splash*, *menu*,
+	*dropdown_menu*, *popup_menu*, *tooltip*, *notification*); the
+	i3-save-tree anchored form _^name$_ is accepted, but regex
+	alternation such as _^(normal|dialog)$_ is rejected, split such
+	patterns into multiple swallows entries (which match as OR).
 
 	A minimal example targeting one Wayland and one xwayland window in
 	a vertical split:

sway/tree/load_layout.c

@@ -251,27 +251,45 @@ static bool append_bare(char **buf, const char *key, const char *value) {
 	return written >= 0;
 }
 
-// i3-save-tree emits window_type as a regex-anchored enum name like
-// "^normal$". The criteria parser treats window_type as a bare enum token,
-// not a regex, so the anchored form fails. Strip a single leading ^ and a
-// single trailing $ before passing through.
-static char *unanchor_enum(const char *value) {
+// Sway's criteria parser treats window_type as a bare enum token, not a
+// regex. To stay i3-save-tree compatible we accept the anchored literal form
+// "^name$" (and the unanchored "name") and reject everything else with a
+// clear error rather than silently dropping the constraint via ATOM_LAST.
+// Real regex constructs like "^(normal|dialog)$" are not supported; users
+// who want alternation should split into multiple swallow entries (which
+// match as OR).
+static const char *known_window_types[] = {
+	"normal", "dialog", "utility", "toolbar", "splash", "menu",
+	"dropdown_menu", "popup_menu", "tooltip", "notification", NULL,
+};
+
+// Strip a single leading ^ and a single trailing $, then validate that the
+// remainder is one of the known atom names. Returns the bare name on
+// success, or NULL with *error_out populated on failure.
+static char *parse_window_type_value(const char *value, char **error_out) {
 	size_t n = strlen(value);
-	size_t start = 0;
-	size_t end = n;
-	if (n > 0 && value[0] == '^') {
-		start = 1;
-	}
-	if (end > start && value[end - 1] == '$') {
-		end--;
-	}
-	char *out = malloc(end - start + 1);
-	if (!out) {
+	size_t start = (n > 0 && value[0] == '^') ? 1 : 0;
+	size_t end = (n > start && value[n - 1] == '$') ? n - 1 : n;
+	size_t bare_len = end - start;
+	char *bare = malloc(bare_len + 1);
+	if (!bare) {
+		*error_out = format_str("append_layout: out of memory");
 		return NULL;
 	}
-	memcpy(out, value + start, end - start);
-	out[end - start] = '\0';
-	return out;
+	memcpy(bare, value + start, bare_len);
+	bare[bare_len] = '\0';
+	for (int i = 0; known_window_types[i]; i++) {
+		if (strcasecmp(bare, known_window_types[i]) == 0) {
+			return bare;
+		}
+	}
+	*error_out = format_str("append_layout: window_type %s is not a "
+			"supported literal value (use one of: normal, dialog, "
+			"utility, toolbar, splash, menu, dropdown_menu, popup_menu, "
+			"tooltip, notification; regex alternation is not supported, "
+			"split into multiple swallow entries instead)", value);
+	free(bare);
+	return NULL;
 }
 
 // Build a single criteria from one entry of a swallows array. The entry is a
@@ -316,8 +334,13 @@ static struct criteria *build_swallow_criteria(struct json_object *entry,
 					"append_layout: swallows.window_type is not a string");
 			return NULL;
 		}
-		char *bare = unanchor_enum(json_object_get_string(wt));
-		if (!bare || !append_bare(&body, "window_type", bare)) {
+		char *bare = parse_window_type_value(json_object_get_string(wt),
+				error_out);
+		if (!bare) {
+			free(body);
+			return NULL;
+		}
+		if (!append_bare(&body, "window_type", bare)) {
 			free(bare);
 			free(body);
 			*error_out = format_str("append_layout: out of memory");