Implement the new spotlight layout

src/grid/SpotlightLayout.tsx

@@ -0,0 +1,89 @@
+/*
+Copyright 2024 New Vector Ltd
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+import { CSSProperties, forwardRef } from "react";
+import { useObservableEagerState } from "observable-hooks";
+
+import { CallLayout } from "./CallLayout";
+import { SpotlightLayout as SpotlightLayoutModel } from "../state/CallViewModel";
+import { useReactiveState } from "../useReactiveState";
+import styles from "./SpotlightLayout.module.css";
+import { Slot } from "./Grid";
+
+interface GridCSSProperties extends CSSProperties {
+  "--grid-columns": number;
+}
+
+const getGridColumns = (gridLength: number): number =>
+  gridLength > 20 ? 2 : 1;
+
+export const makeSpotlightLayout: CallLayout<SpotlightLayoutModel> = ({
+  minBounds,
+}) => ({
+  fixed: {
+    tiles: (model) => new Map([["spotlight", model.spotlight]]),
+    Layout: forwardRef(function SpotlightLayoutFixed({ model }, ref) {
+      const { width, height } = useObservableEagerState(minBounds);
+      const gridColumns = getGridColumns(model.grid.length);
+      const [generation] = useReactiveState<number>(
+        (prev) => (prev === undefined ? 0 : prev + 1),
+        [model.grid.length, width, height],
+      );
+
+      return (
+        <div
+          ref={ref}
+          data-generation={generation}
+          className={styles.fixed}
+          style={{ "--grid-columns": gridColumns, height } as GridCSSProperties}
+        >
+          <div className={styles.spotlight}>
+            <Slot className={styles.slot} tile="spotlight" />
+          </div>
+          <div className={styles.grid} />
+        </div>
+      );
+    }),
+  },
+
+  scrolling: {
+    tiles: (model) => new Map(model.grid.map((tile) => [tile.id, tile])),
+    Layout: forwardRef(function SpotlightLayoutScrolling({ model }, ref) {
+      const { width, height } = useObservableEagerState(minBounds);
+      const gridColumns = getGridColumns(model.grid.length);
+      const [generation] = useReactiveState<number>(
+        (prev) => (prev === undefined ? 0 : prev + 1),
+        [model.grid, width, height],
+      );
+
+      return (
+        <div
+          ref={ref}
+          data-generation={generation}
+          className={styles.scrolling}
+          style={{ "--grid-columns": gridColumns } as GridCSSProperties}
+        >
+          <div className={styles.spotlight} />
+          <div className={styles.grid}>
+            {model.grid.map((tile) => (
+              <Slot key={tile.id} className={styles.slot} tile={tile.id} />
+            ))}
+          </div>
+        </div>
+      );
+    }),
+  },
+});