From 4d4ef5eed536c373f93c766f4071e14665a9b00e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20Ekl=C3=B6f?= <daniel@ekloef.se>
Date: Sat, 20 Apr 2024 08:19:58 +0200
Subject: [PATCH] dcs: XTGETTCAP: handle empty request

If the XTGETTCAP request is empty (no capabilities in it), reply with
an empty error reply.

Closes #1694
---
 CHANGELOG.md | 3 +++
 dcs.c        | 6 ++++++
 2 files changed, 9 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2851f7ba..7d7cd49b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -62,6 +62,9 @@
 * Crash when zooming in or out, with `dpi-aware=yes`, and the
   monitor's DPI is 0 (this is true for, for example, nested Wayland
   sessions, or in virtualized environments).
+* No error response for empty `XTGETTCAP` request ([#1694][1694]).
+
+[1694]: https://codeberg.org/dnkl/foot/issues/1694
 
 
 ### Security
diff --git a/dcs.c b/dcs.c
index 19cce3c2..4dccbdee 100644
--- a/dcs.c
+++ b/dcs.c
@@ -200,6 +200,12 @@ xtgettcap_unhook(struct terminal *term)
     const char *const end = (const char *)&term->vt.dcs.data[left];
     const char *p = (const char *)term->vt.dcs.data;
 
+    if (p == NULL) {
+        /* Request is empty; send an error reply, without any capabilities */
+        term_to_slave(term, "\033P0+r\033\\", 7);
+        return;
+    }
+
     while (true) {
         const char *sep = memchr(p, ';', left);
         size_t cap_len;