Print window manager in -help output

include/xcb.h

@@ -249,4 +249,11 @@ void cairo_image_surface_blur(cairo_surface_t *surface, double radius,
 void x11_event_handler_fowarding(xcb_xim_t *im, xcb_xic_t ic,
                                  xcb_key_press_event_t *event, void *user_data);
 #endif
+
+/**
+ * Get the currently detected window manager.
+ *
+ * @returns NULL when non found, otherwise a string (free with g_free)
+ */
+char *x11_helper_get_window_manager(void);
 #endif

source/rofi.c

@@ -358,6 +358,15 @@ static void help(G_GNUC_UNUSED int argc, char **argv) {
   printf("Global options:\n");
   print_options();
   printf("\n");
+  printf("Detected Window manager:\n");
+  char *wm = x11_helper_get_window_manager();
+  if (wm) {
+    printf("\t• %s\n", wm);
+    g_free(wm);
+  } else {
+    printf("\t• No window manager detected.\n");
+  }
+  printf("\n");
   display_dump_monitor_layout();
   printf("\n");
   printf("Detected modes:\n");

source/xcb.c

@@ -1607,6 +1607,26 @@ static void x11_create_frequently_used_atoms(void) {
   }
 }
 
+char *x11_helper_get_window_manager(void) {
+  char *retv = NULL;
+  xcb_window_t wm_win = 0;
+  xcb_get_property_cookie_t cc = xcb_ewmh_get_supporting_wm_check_unchecked(
+      &xcb->ewmh, xcb_stuff_get_root_window());
+
+  if (xcb_ewmh_get_supporting_wm_check_reply(&xcb->ewmh, cc, &wm_win, NULL)) {
+    xcb_ewmh_get_utf8_strings_reply_t wtitle;
+    xcb_get_property_cookie_t cookie =
+        xcb_ewmh_get_wm_name_unchecked(&(xcb->ewmh), wm_win);
+    if (xcb_ewmh_get_wm_name_reply(&(xcb->ewmh), cookie, &wtitle, (void *)0)) {
+      if (wtitle.strings_len > 0) {
+        retv = g_strdup(wtitle.strings);
+      }
+      xcb_ewmh_get_utf8_strings_reply_wipe(&wtitle);
+    }
+  }
+  return retv;
+}
+
 static void x11_helper_discover_window_manager(void) {
   xcb_window_t wm_win = 0;
   xcb_get_property_cookie_t cc = xcb_ewmh_get_supporting_wm_check_unchecked(