[Dmenu][Script] Add support for fallback icons

doc/rofi-script.5.markdown

@@ -138,7 +138,7 @@ For example:
 
 The following options are supported:
 
--   **icon**: Set the icon for that row.
+-   **icon**: Set the icon for that row. Multiple fallback icons can be specified using comma-separated values.
 
 -   **display**: Replace the displayed string. (Original string will still be used for filtering)
 
@@ -158,7 +158,7 @@ The following options are supported:
 multiple entries can be passed using the `\x1f` separator.
 
 ```bash
-    echo -en "aap\0icon\x1ffolder\x1finfo\x1ftest\n"
+    echo -en "aap\0icon\x1ffolder,inode-directory\x1finfo\x1ftest\n"
 ```
 
 ## Executing external program

source/modes/dmenu.c

@@ -724,12 +724,32 @@ static cairo_surface_t *dmenu_get_icon(const Mode *sw,
   if (dr->icon_name == NULL) {
     return NULL;
   }
-  uint32_t uid = dr->icon_fetch_uid =
+  if (strchr(dr->icon_name, ',') == NULL) {
+    uint32_t uid = dr->icon_fetch_uid =
       rofi_icon_fetcher_query(dr->icon_name, height);
   dr->icon_fetch_size = height;
   dr->icon_fetch_scale = scale;
 
-  return rofi_icon_fetcher_get(uid);
+    return rofi_icon_fetcher_get(uid);
+  } else {
+    cairo_surface_t *icon_surface = NULL;
+    char *icon_name_copy = g_strdup(dr->icon_name);
+    char *icon_iter = icon_name_copy;
+    char *icon = NULL;
+    // Try each icon in the comma-separated list until one is found
+    while ((icon = strsep(&icon_iter, ",")) != NULL) {
+      uint32_t uid = rofi_icon_fetcher_query(icon, height);
+      icon_surface = rofi_icon_fetcher_get(uid);
+      if (icon_surface != NULL) {
+        dr->icon_fetch_uid = uid;
+        dr->icon_fetch_size = height;
+        dr->icon_fetch_scale = scale;
+        break;
+      }
+    }
+    g_free(icon_name_copy);
+    return icon_surface;
+  }
 }
 
 static void dmenu_finish(DmenuModePrivateData *pd, RofiViewState *state,