wayland: add WMAKER_USE_WAYLAND backend selector and split smoke tests

- startup.c: include wl_backend.h when USE_WAYLAND_BACKEND is defined;
  select wl_backend when WMAKER_USE_WAYLAND env var is set, otherwise
  fall back to x11_backend (no-op for non-Wayland builds)
- tests/smoke-test.sh renamed to tests/x11-smoke-test.sh (X11-only path)
- tests/wl-smoke-test.sh: new Wayland smoke test; currently verifies
  wl_backend symbol presence and wlroots linkage; headless compositor
  tests will be added as vtable slots are implemented

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/startup.c

@@ -49,6 +49,9 @@
 #include "session.h"
 #include "defaults.h"
 #include "backend/x11/x11_backend.h"
+#ifdef USE_WAYLAND_BACKEND
+#include "backend/wayland/wl_backend.h"
+#endif
 #include "properties.h"
 #include "dialog.h"
 #include "wmspec.h"
@@ -520,7 +523,12 @@ void StartUp(Bool defaultScreenOnly)
 	w_global.screen_count = 0;
 
 	/* Select the display backend before any screen is initialized. */
-	wm_backend = &x11_backend;
+#ifdef USE_WAYLAND_BACKEND
+	if (getenv("WMAKER_USE_WAYLAND"))
+		wm_backend = &wl_backend;
+	else
+#endif
+		wm_backend = &x11_backend;
 
 	/* Check if TIFF images are supported */
 	formats = RSupportedFileFormats();

tests/wl-smoke-test.sh

@@ -0,0 +1,41 @@
+#!/bin/sh
+# tests/wl-smoke-test.sh
+#
+# Wayland backend smoke test for Window Maker.
+# Uses the wlroots headless compositor (no display hardware needed).
+#
+# Currently verifies:
+#   1. wmaker was built with Wayland backend support (symbol present)
+#   2. wmaker links against wlroots
+#
+# This test grows as wl_backend vtable slots are implemented.
+# When the compositor can open a headless display, tests for window
+# management, EWMH properties, etc. will be added here in the same
+# style as tests/x11-smoke-test.sh.
+#
+# Exit 0 = PASS, non-zero = FAIL.
+
+set -e
+
+# Use the real ELF binary (src/wmaker is a libtool wrapper script)
+WMAKER=src/.libs/wmaker
+[ -x "$WMAKER" ] || WMAKER=src/wmaker
+
+die() {
+    echo "FAIL: $*" >&2
+    exit 1
+}
+
+# -- 1. Build check: wl_backend symbol must be present --------------------
+[ -x "$WMAKER" ] || die "wmaker binary not found (tried src/.libs/wmaker and src/wmaker)"
+
+nm "$WMAKER" 2>/dev/null | grep -q 'wl_backend' \
+    || die "wl_backend symbol not found in $WMAKER (built without --enable-wayland-backend?)"
+
+# -- 2. Link check: wlroots library must be linked in ---------------------
+ldd "$WMAKER" 2>/dev/null | grep -qi 'wlroots\|libwlr' \
+    || die "wmaker does not link against wlroots"
+
+# -- Done (headless compositor tests to be added as vtable is implemented) --
+echo "PASS (wl_backend symbol + wlroots link verified; full headless tests pending)"
+exit 0