WIP: Add --enable-sixel configure flag.

Makefile.am

@@ -154,7 +154,6 @@ dist_tmux_SOURCES = \
 	hyperlinks.c \
 	input-keys.c \
 	input.c \
-	image.c \
 	job.c \
 	key-bindings.c \
 	key-string.c \
@@ -181,7 +180,6 @@ dist_tmux_SOURCES = \
 	server-fn.c \
 	server.c \
 	session.c \
-	sixel.c \
 	spawn.c \
 	status.c \
 	style.c \
@@ -220,6 +218,12 @@ if HAVE_UTF8PROC
 nodist_tmux_SOURCES += compat/utf8proc.c
 endif
 
+# Enable sixel support.
+if ENABLE_SIXEL
+dist_tmux_SOURCES += sixel/sixel.c
+dist_tmux_SOURCES += sixel/image.c
+endif
+
 if NEED_FUZZING
 check_PROGRAMS = fuzz/input-fuzzer
 fuzz_input_fuzzer_LDFLAGS = $(FUZZING_LIBS)

configure.ac

@@ -440,6 +440,16 @@ if test "x$enable_cgroups" = xyes; then
 	fi
 fi
 
+# Enable sixel support.
+AC_ARG_ENABLE(
+	sixel,
+	AS_HELP_STRING(--enable-sixel, enable sixel images)
+)
+if test "x$enable_sixel" = xyes; then
+	AC_DEFINE(ENABLE_SIXEL)
+fi
+AM_CONDITIONAL(ENABLE_SIXEL, [test "x$enable_sixel" = xyes])
+
 # Check for b64_ntop. If we have b64_ntop, we assume b64_pton as well.
 AC_MSG_CHECKING(for b64_ntop)
 	AC_LINK_IFELSE([AC_LANG_PROGRAM(