102 lines
3.9 KiB
Plaintext
102 lines
3.9 KiB
Plaintext
/*
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* Copyright 2020 Adobe. All rights reserved.
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* This file is licensed to you under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License. You may obtain a copy
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* of the License at http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software distributed under
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* the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR REPRESENTATIONS
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* OF ANY KIND, either express or implied. See the License for the specific language
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* governing permissions and limitations under the License.
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*/
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import {InvalidationContext} from './types';
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import {ItemDropTarget, Key, LayoutDelegate, Node} from '@react-types/shared';
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import {LayoutInfo} from './LayoutInfo';
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import {Rect} from './Rect';
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import {Size} from './Size';
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import {Virtualizer} from './Virtualizer';
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/**
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* Virtualizer supports arbitrary layout objects, which compute what items are visible, and how
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* to position and style them. However, layouts do not render items directly. Instead,
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* layouts produce lightweight LayoutInfo objects which describe various properties of an item,
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* such as its position and size. The Virtualizer is then responsible for creating the actual
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* views as needed, based on this layout information.
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*
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* Every layout extends from the Layout abstract base class. Layouts must implement the `getVisibleLayoutInfos`,
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* `getLayoutInfo`, and `getContentSize` methods. All other methods can be optionally overridden to implement custom behavior.
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*/
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export abstract class Layout<T extends object = Node<any>, O = any> implements LayoutDelegate {
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/** The Virtualizer the layout is currently attached to. */
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virtualizer: Virtualizer<T, any> | null = null;
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/**
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* Returns an array of `LayoutInfo` objects which are inside the given rectangle.
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* Should be implemented by subclasses.
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* @param rect The rectangle that should contain the returned LayoutInfo objects.
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*/
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abstract getVisibleLayoutInfos(rect: Rect): LayoutInfo[];
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/**
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* Returns a `LayoutInfo` for the given key.
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* Should be implemented by subclasses.
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* @param key The key of the LayoutInfo to retrieve.
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*/
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abstract getLayoutInfo(key: Key): LayoutInfo | null;
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/**
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* Returns size of the content. By default, it returns virtualizer's size.
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*/
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abstract getContentSize(): Size;
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/**
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* Returns whether the layout should invalidate in response to
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* visible rectangle changes. By default, it only invalidates
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* when the virtualizer's size changes. Return true always
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* to make the layout invalidate while scrolling (e.g. sticky headers).
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*/
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shouldInvalidate(newRect: Rect, oldRect: Rect): boolean {
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// By default, invalidate when the size changes
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return newRect.width !== oldRect.width
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|| newRect.height !== oldRect.height;
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}
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/**
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* Returns whether the layout should invalidate when the layout options change.
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* By default it invalidates when the object identity changes. Override this
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* method to optimize layout updates based on specific option changes.
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*/
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shouldInvalidateLayoutOptions(newOptions: O, oldOptions: O): boolean {
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return newOptions !== oldOptions;
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}
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/**
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* This method allows the layout to perform any pre-computation
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* it needs to in order to prepare LayoutInfos for retrieval.
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* Called by the virtualizer before `getVisibleLayoutInfos`
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* or `getLayoutInfo` are called.
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*/
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update(invalidationContext: InvalidationContext<O>): void {} // eslint-disable-line @typescript-eslint/no-unused-vars
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/**
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* Updates the size of the given item.
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*/
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updateItemSize?(key: Key, size: Size): boolean;
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/**
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* Returns a `LayoutInfo` for the given drop target.
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*/
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getDropTargetLayoutInfo?(target: ItemDropTarget): LayoutInfo;
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/** @private */
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getItemRect(key: Key): Rect | null {
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return this.getLayoutInfo(key)?.rect ?? null;
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}
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/** @private */
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getVisibleRect(): Rect {
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return this.virtualizer!.visibleRect;
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}
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}
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