Add warnings about invalid output commands

This handles some cases where sway will crash if an output command is
invalid/missing an argument.

1 files changed, 8 insertions, 2 deletions

diff --git a/sway/commands.c b/sway/commands.c
index a46a0b89..42845f65 100644
--- a/sway/commands.c
+++ b/sway/commands.c
@@ -767,8 +767,14 @@ static struct cmd_results *cmd_output(int argc, char **argv) {
                         output->y = y;
                 } else if (strcasecmp(argv[i], "bg") == 0 || strcasecmp(argv[i], "background") == 0) {
                         wordexp_t p;
-                        char *src = argv[++i];
-                        char *mode = argv[++i];
+                        if (++i >= argc) {
+                                return cmd_results_new(CMD_INVALID, "output", "Missing background file.");
+                        }
+                        char *src = argv[i];
+                        if (++i >= argc) {
+                                return cmd_results_new(CMD_INVALID, "output", "Missing background scaling mode.");
+                        }
+                        char *mode = argv[i];
                         if (wordexp(src, &p, 0) != 0) {
                                 return cmd_results_new(CMD_INVALID, "output", "Invalid syntax (%s)", src);
                         }