From 843e0f528ca586758bd707431742c172a1ea4c50 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Przemek=20Wi=C4=99ch?= <pwiech@gmail.com>
Date: Thu, 11 Jun 2026 17:09:30 +0200
Subject: [PATCH] Shift `config` to URL as source of truth

---
 docs/APP_REFACTORING_DESIGN.md |  2 +-
 src/app.tsx                    | 21 +++++++--------------
 2 files changed, 8 insertions(+), 15 deletions(-)

diff --git a/docs/APP_REFACTORING_DESIGN.md b/docs/APP_REFACTORING_DESIGN.md
index 0b27668..5b4dc92 100644
--- a/docs/APP_REFACTORING_DESIGN.md
+++ b/docs/APP_REFACTORING_DESIGN.md
@@ -97,7 +97,7 @@ We will gradually eliminate React state variables in `src/app.tsx` and derive th
 *   [x] **Step 3.1d:** Shift `freezeAnimation` to URL as SSOT. Derive it directly from search parameters on render and remove its React state variable.
 *   [x] **Step 3.2:** Extract `selection` and `detailIndi` state. Parse them directly from URL params (`indi`, `gen`, and `detail`); update display selectors. Remove React states. Ensure that chart selection changes (`onSelection` callback) explicitly clear or update the `detail` query parameter to match the new selection to avoid getting stuck on the old details viewport. Also update the detail-only selection handler (`onDetailSelection`) to update the `detail` query parameter in the URL.
 *   [x] **Step 3.3:** Extract `showSidePanel` state. Derive state directly from `?sidePanel=` parameter. Remove React state. Enhance URL args helpers to allow generating path/query target objects with replaced values, and ensure layout settings (`sidePanel`) and configuration changes use `replace: true` to prevent polluting the browser history stack.
-*   [ ] **Step 3.4:** Extract `config` state. Parse display settings on render using `argsToConfig` helper. Remove state. In `ViewPage`, run `updateChartWithConfig(config, data)` synchronously during the render pass (e.g. in the `useMemo` that derives query parameters/config) to update the in-memory chart data before it is rendered by the `<Chart>` child component. Run E2E and visual tests to verify no rendering regressions occurred.
+*   [x] **Step 3.4:** Extract `config` state. Parse display settings on render using `argsToConfig` helper. Remove state. In `ViewPage`, run `updateChartWithConfig(config, data)` synchronously during the render pass (e.g. in the `useMemo` that derives query parameters/config) to update the in-memory chart data before it is rendered by the `<Chart>` child component. Run E2E and visual tests to verify no rendering regressions occurred.
 
 #### Phase 4: Structural Page Nesting
 *   [ ] **Step 4.1:** Create `src/hooks/use_google_auth.ts` to manage Google Drive authentication token updates. Remove `hasGoogleToken` state from `src/app.tsx`.
diff --git a/src/app.tsx b/src/app.tsx
index 2b11796..b3f167e 100644
--- a/src/app.tsx
+++ b/src/app.tsx
@@ -47,13 +47,7 @@ import {useWebMcpBridge} from './hooks/use_webmcp_bridge';
 import {Intro} from './intro';
 import {GoogleAuthModal} from './menu/google_auth_modal';
 import {TopBar} from './menu/top_bar';
-import {
-  Config,
-  configToArgs,
-  DEFALUT_CONFIG,
-  Ids,
-  Sex,
-} from './sidepanel/config/config';
+import {Config, configToArgs, Ids, Sex} from './sidepanel/config/config';
 import {SidePanel} from './sidepanel/side-panel';
 import {analyticsEvent} from './util/analytics';
 import {TopolaError} from './util/error';
@@ -92,9 +86,6 @@ export function App() {
   /** Specification of the source of the data. */
   const [sourceSpec, setSourceSpec] = useState<DataSourceSpec>();
 
-  /** Configuration settings for chart display options (e.g. colors, hiding IDs). */
-  const [config, setConfig] = useState(DEFALUT_CONFIG);
-
   /** Controls the visibility of the Google Drive OAuth permission modal. */
   const [showAuthModal, setShowAuthModal] = useState(false);
   /** Stores the file ID that failed to load from Google Drive due to authorization errors. */
@@ -122,6 +113,12 @@ export function App() {
   const freezeAnimation = args.freezeAnimation;
   /** Whether the side panel is shown. */
   const showSidePanel = args.showSidePanel;
+  /** Configuration settings for chart display options (e.g. colors, hiding IDs). */
+  const config = args.config;
+
+  useMemo(() => {
+    updateChartWithConfig(config, data);
+  }, [config, data]);
   /** The currently selected individual. Fallback to default individual from loaded data if not specified. */
   const updatedSelection = useMemo(() => {
     return data ? getSelection(data.chartData, args.selection) : undefined;
@@ -345,7 +342,6 @@ export function App() {
         setState(AppState.LOADING);
         // Set state from URL parameters.
         setSourceSpec(args.sourceSpec);
-        setConfig(args.config);
         const currentFetchId = ++fetchIdRef.current;
         setLoadingStatus('Loading…');
         try {
@@ -369,7 +365,6 @@ export function App() {
             data.chartData,
             args.selection,
           );
-          updateChartWithConfig(args.config, data);
           setState(AppState.SHOWING_CHART);
         } catch (error: unknown) {
           if (!isMountedRef.current || fetchIdRef.current !== currentFetchId) {
@@ -587,8 +582,6 @@ export function App() {
                 expanded={showSidePanel}
                 onToggle={onToggleSidePanel}
                 onConfigChange={(config) => {
-                  setConfig(config);
-                  updateChartWithConfig(config, data);
                   updateUrl(configToArgs(config), {replace: true});
                 }}
               />