[vte] parser: cat: Make linter warn on unsupported DECSIXEL OR-mode

[Christian Persch <chpe src gnome org>]

commit d4e0d89c6c782f380abf293a822eb7993d588067
Author: Christian Persch <chpe src gnome org>
Date:   Thu Dec 24 13:50:18 2020 +0100

    parser: cat: Make linter warn on unsupported DECSIXEL OR-mode

 src/parser-cat.cc | 8 ++++++++
 1 file changed, 8 insertions(+)
---
diff --git a/src/parser-cat.cc b/src/parser-cat.cc
index a5d9fd35..b9f40616 100644
--- a/src/parser-cat.cc
+++ b/src/parser-cat.cc
@@ -753,6 +753,14 @@ public:
                         check_sgr(seq);
                         break;
 
+                case VTE_CMD_DECSIXEL:
+                        /* OR mode is a nonstandard NetBSD/x68k extension that is
+                         * not supported in VTE.
+                         */
+                        if (seq.collect1(1) == 5)
+                                warn("DECSIXEL OR-mode not supported");
+                        break;
+
                 default:
                         if (cmd >= VTE_CMD_NOP_FIRST)
                                 warn("%s is unimplemented", cmd_to_str(cmd));