Initial structure for shared component views (#30216)

* Very first pass at shared component views

Turn the trivial TextualEvent into a shared component with a separate view
model for element web. Args to view model will probably change to be more
specific and VM typer needs abstracting out into an interface, but should
give the general idea.

* Remove old TextualEvent

* Pass showHiddenEvents

Because we used it anyway, we just cheated by getting it from the context

* Factor out common view model stuff

* Move ViewModel interface into the shared components

* Add tiny wrapper hook

* Move showHiddenEvents into props fully

* Fill in stories / test

* chore: setup storybook

cherry pick edc5e8705674b8708d986910b02b5d2545777fb3
from florianduros/storybook

* Add TextualEvent component to storybook

* Add mock view model & snapshot

* Remove old style stories entry

* Change import

* Change import

* Prettier

* Add paxckage patch to @types/mdx

for React 19 compat

* Pass getSnapshot as getServerSnapshot too

* Maybe make sonar regognise tests as tests

* Typo

* Use storybook reacvt-vite

There's no reason to use the react-webpack plugin just because our app
is stuck on webpack, it just means we have vite as a dependency too.

* Change here too

* Workaround for incomatible types in rollup

https://github.com/rollup/rollup/issues/5199

* Remove webpack styling addon

Not necessary now we're using vite

* Hopefully do screenshot testing...

* need newer node

* quote issues

* Make it an npm script

* colons

* use right port

* Install playwright browsers

* Try without the if

* Oh right, we need the headless shell

* Pass flag to store received screenshots

and upload diffs too

* Update snapshot from received

* Include platform in snapshot / received dir

because font rendering differs between platforms

* Suffix snapshots with platform instead

like we do for playwright

* Remove unnecessary env vars

and better name

* Add some comments

* Prettier

* Fix yarn.lock

* Memoise vm creation

Co-authored-by: Florian Duros <florianduros@element.io>

* Add implements

Co-authored-by: Florian Duros <florianduros@element.io>

* Fix listener interface

* Add implements

Co-authored-by: Florian Duros <florianduros@element.io>

* Fix types

* Fix more types

* Revert useMemo

as this isn't a hook

* Unused import

* Add missing playwright step

* Add return type annotation

* Change to add / remove subscription callback

* Change to 'add' rather than 'subs.subscribe'

* Add cache specifier for only shell playwright browsers

* Add copyright headers

---------

Co-authored-by: Florian Duros <florian.duros@ormaz.fr>
Co-authored-by: Florian Duros <florianduros@element.io>

src/shared-components/MockViewModel.ts

@@ -0,0 +1,23 @@
+/*
+Copyright 2025 New Vector Ltd.
+
+SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
+Please see LICENSE files in the repository root for full details.
+*/
+
+import { type ViewModel } from "./ViewModel";
+
+/**
+ * A mock view model that returns a static snapshot passed in the constructor, with no updates.
+ */
+export class MockViewModel<T> implements ViewModel<T> {
+    public constructor(private snapshot: T) {}
+
+    public getSnapshot = (): T => {
+        return this.snapshot;
+    };
+
+    public subscribe(listener: () => void): () => void {
+        return () => undefined;
+    }
+}

src/shared-components/ViewModel.ts

@@ -0,0 +1,23 @@
+/*
+Copyright 2025 New Vector Ltd.
+
+SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only OR LicenseRef-Element-Commercial
+Please see LICENSE files in the repository root for full details.
+*/
+
+/**
+ * The interface for a generic View Model passed to the shared components.
+ * The snapshot is of type T which is a type specifying a snapshot for the view in question.
+ */
+export interface ViewModel<T> {
+    /**
+     * The current snapshot of the view model.
+     */
+    getSnapshot: () => T;
+
+    /**
+     * Subscribes to changes in the view model.
+     * The listener will be called whenever the snapshot changes.
+     */
+    subscribe: (listener: () => void) => () => void;
+}

src/shared-components/event-tiles/TextualEvent/TextualEvent.stories.tsx

@@ -0,0 +1,25 @@
+/*
+Copyright 2025 New Vector Ltd.
+
+SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
+Please see LICENSE files in the repository root for full details.
+*/
+
+import React from "react";
+import { type Meta, type StoryFn } from "@storybook/react-vite";
+
+import { TextualEvent as TextualEventComponent } from "./TextualEvent";
+import { MockViewModel } from "../../MockViewModel";
+
+export default {
+    title: "Event/TextualEvent",
+    component: TextualEventComponent,
+    tags: ["autodocs"],
+    args: {
+        vm: new MockViewModel("Dummy textual event text"),
+    },
+} as Meta<typeof TextualEventComponent>;
+
+const Template: StoryFn<typeof TextualEventComponent> = (args) => <TextualEventComponent {...args} />;
+
+export const Default = Template.bind({});

src/shared-components/event-tiles/TextualEvent/TextualEvent.test.tsx

@@ -0,0 +1,21 @@
+/*
+Copyright 2025 New Vector Ltd.
+
+SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only OR LicenseRef-Element-Commercial
+Please see LICENSE files in the repository root for full details.
+*/
+
+import { composeStories } from "@storybook/react-vite";
+import { render } from "jest-matrix-react";
+import React from "react";
+
+import * as stories from "./TextualEvent.stories.tsx";
+
+const { Default } = composeStories(stories);
+
+describe("TextualEvent", () => {
+    it("renders a textual event", () => {
+        const { container } = render(<Default />);
+        expect(container).toMatchSnapshot();
+    });
+});

src/shared-components/event-tiles/TextualEvent/TextualEvent.tsx

@@ -0,0 +1,23 @@
+/*
+Copyright 2025 New Vector Ltd.
+
+SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only OR LicenseRef-Element-Commercial
+Please see LICENSE files in the repository root for full details.
+*/
+
+import React, { type ReactNode, type JSX } from "react";
+
+import { type ViewModel } from "../../ViewModel";
+import { useViewModel } from "../../useViewModel";
+
+export type TextualEventViewSnapshot = string | ReactNode;
+
+export interface Props {
+    vm: ViewModel<TextualEventViewSnapshot>;
+}
+
+export function TextualEvent({ vm }: Props): JSX.Element {
+    const contents = useViewModel(vm);
+
+    return <div className="mx_TextualEvent">{contents}</div>;
+}

src/shared-components/event-tiles/TextualEvent/__snapshots__/TextualEvent.test.tsx.snap

@@ -0,0 +1,11 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`TextualEvent renders a textual event 1`] = `
+<div>
+  <div
+    class="mx_TextualEvent"
+  >
+    Dummy textual event text
+  </div>
+</div>
+`;

src/shared-components/event-tiles/TextualEvent/index.ts

@@ -0,0 +1,8 @@
+/*
+Copyright 2025 New Vector Ltd.
+
+SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only OR LicenseRef-Element-Commercial
+Please see LICENSE files in the repository root for full details.
+*/
+
+export { TextualEvent } from "./TextualEvent";

src/shared-components/useViewModel.ts

@@ -0,0 +1,21 @@
+/*
+Copyright 2025 New Vector Ltd.
+
+SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only OR LicenseRef-Element-Commercial
+Please see LICENSE files in the repository root for full details.
+*/
+
+import { useSyncExternalStore } from "react";
+
+import { type ViewModel } from "./ViewModel";
+
+/**
+ * A small wrapper around useSyncExternalStore to use a view model in a shared component view
+ * @param vm The view model to use
+ * @returns The current snapshot
+ */
+export function useViewModel<T>(vm: ViewModel<T>): T {
+    // We need to pass the same getSnapshot function as getServerSnapshot as this
+    // is used when making the HTML chat export.
+    return useSyncExternalStore(vm.subscribe, vm.getSnapshot, vm.getSnapshot);
+}