Wedge t3chguy's resizer prototype into the sublist

src/stores/room-list/ListLayout.ts

@@ -0,0 +1,65 @@
+/*
+Copyright 2020 The Matrix.org Foundation C.I.C.
+
+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.
+*/
+
+const TILE_HEIGHT_PX = 34;
+
+interface ISerializedListLayout {
+    numTiles: number;
+}
+
+export class ListLayout {
+    private _n = 0;
+
+    constructor(public readonly tagId) {
+        const serialized = localStorage.getItem(this.key);
+        if (serialized) {
+            // We don't use the setters as they cause writes.
+            const parsed = <ISerializedListLayout>JSON.parse(serialized);
+            this._n = parsed.numTiles;
+        }
+    }
+
+    public get tileHeight(): number {
+        return TILE_HEIGHT_PX;
+    }
+
+    private get key(): string {
+        return `mx_sublist_layout_${this.tagId}_boxed`;
+    }
+
+    public get visibleTiles(): number {
+        return Math.max(this._n, this.minVisibleTiles);
+    }
+
+    public set visibleTiles(v: number) {
+        this._n = v;
+        localStorage.setItem(this.key, JSON.stringify(this.serialize()));
+    }
+
+    public get minVisibleTiles(): number {
+        return 3;
+    }
+
+    public tilesToPixels(n: number): number {
+        return n * this.tileHeight;
+    }
+
+    private serialize(): ISerializedListLayout {
+        return {
+            numTiles: this.visibleTiles,
+        };
+    }
+}