feat: support reverse-proxy URL subpaths (llama-swap, SwarmUI) (#1122)

web/comfyui/base_path.js

@@ -0,0 +1,19 @@
+/**
+ * Base-path helpers for code running inside the ComfyUI page.
+ *
+ * When ComfyUI is served under a URL subpath by a reverse proxy (e.g.
+ * llama-swap serves it at "/comfyui/", SwarmUI at "/ComfyBackendDirect/"),
+ * the ComfyUI SPA always sits at the root of that prefix, so the prefix is
+ * the current pathname without the trailing slash — the same convention the
+ * ComfyUI frontend uses for its own api_base. Proxies strip the prefix and
+ * forward no headers, so the page URL is the only place to learn it.
+ */
+
+export function getComfyUIBasePath() {
+    const { pathname } = window.location;
+    return pathname.endsWith("/") ? pathname.slice(0, -1) : pathname;
+}
+
+export function lmUrl(path) {
+    return `${getComfyUIBasePath()}${path}`;
+}