element-portable/src/stores/room-list/ListLayout.ts

/*
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.
*/

import { TagID } from "./models";

const TILE_HEIGHT_PX = 44;

// this comes from the CSS where the show more button is
// mathematically this percent of a tile when floating.
const RESIZER_BOX_FACTOR = 0.78;

interface ISerializedListLayout {
    numTiles: number;
    showPreviews: boolean;
    collapsed: boolean;
}

export class ListLayout {
    private _n = 0;
    private _previews = false;
    private _collapsed = false;

    constructor(public readonly tagId: 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;
            this._previews = parsed.showPreviews;
            this._collapsed = parsed.collapsed;
        }
    }

    public get isCollapsed(): boolean {
        return this._collapsed;
    }

    public set isCollapsed(v: boolean) {
        this._collapsed = v;
        this.save();
    }

    public get showPreviews(): boolean {
        return this._previews;
    }

    public set showPreviews(v: boolean) {
        this._previews = v;
        this.save();
    }

    public get tileHeight(): number {
        return TILE_HEIGHT_PX;
    }

    private get key(): string {
        return `mx_sublist_layout_${this.tagId}_boxed`;
    }

    public get visibleTiles(): number {
        if (this._n === 0) return this.defaultVisibleTiles;
        return Math.max(this._n, this.minVisibleTiles);
    }

    public set visibleTiles(v: number) {
        this._n = v;
        this.save();
    }

    public get minVisibleTiles(): number {
        return 1 + RESIZER_BOX_FACTOR;
    }

    public get defaultVisibleTiles(): number {
        // 10 is what "feels right", and mostly subject to design's opinion.
        return 10 + RESIZER_BOX_FACTOR;
    }

    public setVisibleTilesWithin(diff: number, maxPossible: number) {
        if (this.visibleTiles > maxPossible) {
            this.visibleTiles = maxPossible + diff;
        } else {
            this.visibleTiles += diff;
        }
    }

    public calculateTilesToPixelsMin(maxTiles: number, n: number, possiblePadding: number): number {
        // Only apply the padding if we're about to use maxTiles as we need to
        // plan for the padding. If we're using n, the padding is already accounted
        // for by the resizing stuff.
        let padding = 0;
        if (maxTiles < n) {
            padding = possiblePadding;
        }
        return this.tilesToPixels(Math.min(maxTiles, n)) + padding;
    }

    public tilesWithResizerBoxFactor(n: number): number {
        return n + RESIZER_BOX_FACTOR;
    }

    public tilesWithPadding(n: number, paddingPx: number): number {
        return this.pixelsToTiles(this.tilesToPixelsWithPadding(n, paddingPx));
    }

    public tilesToPixelsWithPadding(n: number, paddingPx: number): number {
        return this.tilesToPixels(n) + paddingPx;
    }

    public tilesToPixels(n: number): number {
        return n * this.tileHeight;
    }

    public pixelsToTiles(px: number): number {
        return px / this.tileHeight;
    }

    public reset() {
        localStorage.removeItem(this.key);
    }

    private save() {
        localStorage.setItem(this.key, JSON.stringify(this.serialize()));
    }

    private serialize(): ISerializedListLayout {
        return {
            numTiles: this.visibleTiles,
            showPreviews: this.showPreviews,
            collapsed: this.isCollapsed,
        };
    }
}