remove old js lazylist
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Bruno Windels
parent
9557178ffb
commit
35fb84c275
1 changed files with 0 additions and 287 deletions
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/*
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Copyright 2021 The Matrix.org Foundation C.I.C.
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Licensed 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.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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import {el} from "./html";
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import {mountView} from "./utils";
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import {ListView} from "./ListView";
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import {insertAt} from "./utils";
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import {ItemRange, ScrollDirection} from "./ItemRange.js";
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export class LazyListView extends ListView {
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constructor({itemHeight, overflowMargin = 5, overflowItems = 20,...options}, childCreator) {
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super(options, childCreator);
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this._itemHeight = itemHeight;
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this._overflowMargin = overflowMargin;
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this._overflowItems = overflowItems;
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}
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_getVisibleRange() {
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const length = this._list ? this._list.length : 0;
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const scrollTop = this._parent.scrollTop;
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const topCount = Math.min(Math.max(0, Math.floor(scrollTop / this._itemHeight)), length);
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const itemsAfterTop = length - topCount;
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const visibleItems = this._height !== 0 ? Math.ceil(this._height / this._itemHeight) : 0;
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const renderCount = Math.min(visibleItems, itemsAfterTop);
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const bottomCount = itemsAfterTop - renderCount;
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return new ItemRange(topCount, renderCount, bottomCount);
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}
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_renderIfNeeded() {
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const range = this._getVisibleRange();
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const intersectRange = range.expand(this._overflowMargin);
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const renderRange = range.expand(this._overflowItems);
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// only update render Range if the new range + overflowMargin isn't contained by the old anymore
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if (!this._renderRange.contains(intersectRange)) {
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console.log("new", renderRange);
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console.log("current", this._renderRange);
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console.log("diff", this._renderRange.diff(renderRange));
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this._renderElementsInRange(renderRange);
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}
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}
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async _initialRender() {
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/*
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Wait two frames for the return from mount() to be inserted into DOM.
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This should be enough, but if this gives us trouble we can always use
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MutationObserver.
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*/
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await new Promise(r => requestAnimationFrame(r));
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await new Promise(r => requestAnimationFrame(r));
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this._height = this._parent.clientHeight;
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if (this._height === 0) { console.error("LazyListView could not calculate parent height."); }
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const initialRange = this._getVisibleRange();
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const initialRenderRange = initialRange.expand(this._overflowItems);
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this._renderRange = new ItemRange(0, 0, initialRange.bottomCount + 1);
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this._renderElementsInRange(initialRenderRange);
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}
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_itemsFromList({start, end}) {
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const array = [];
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let i = 0;
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for (const item of this._list) {
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if (i >= start && i <= end) {
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array.push(item);
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}
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i = i + 1;
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}
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return array;
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}
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_itemAtIndex(idx) {
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let i = 0;
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for (const item of this._list) {
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if (i === idx) {
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return item;
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}
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i = i + 1;
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}
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return null;
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}
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_adjustPadding(range) {
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const { topCount, bottomCount } = range;
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const paddingTop = topCount * this._itemHeight;
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const paddingBottom = bottomCount * this._itemHeight;
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this._root.style.paddingTop = `${paddingTop}px`;
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this._root.style.paddingBottom = `${paddingBottom}px`;
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}
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_renderedFragment(items, childInstanceModifier) {
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const fragment = document.createDocumentFragment();
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for (const item of items) {
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const view = this._childCreator(item);
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childInstanceModifier(view);
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fragment.appendChild(mountView(view, this._mountArgs));
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}
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return fragment;
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}
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_renderElementsInRange(range) {
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const diff = this._renderRange.diff(range);
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const renderedItems = this._itemsFromList(diff.toAdd);
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this._adjustPadding(range);
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const {start, end} = diff.toRemove;
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const normalizedStart = this._renderRange.normalize(start);
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this._childInstances.splice(normalizedStart, end - start + 1).forEach(child => this._removeChild(child));
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if (diff.scrollDirection === ScrollDirection.downwards) {
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const fragment = this._renderedFragment(renderedItems, view => this._childInstances.push(view));
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this._root.appendChild(fragment);
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}
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else {
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const fragment = this._renderedFragment(renderedItems, view => this._childInstances.unshift(view));
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this._root.insertBefore(fragment, this._root.firstChild);
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}
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this._renderRange = range;
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}
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mount() {
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const root = super.mount();
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this._subscription = this._list.subscribe(this);
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this._childInstances = [];
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this._parent = el("div", {className: "LazyListParent"}, root);
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/*
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Hooking to scroll events can be expensive.
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Do we need to do more (like event throttling)?
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*/
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this._parent.addEventListener("scroll", () => this._renderIfNeeded());
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this._initialRender();
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return this._parent;
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}
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update(attributes) {
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this._renderRange = null;
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super.update(attributes);
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this._childInstances = [];
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this._initialRender();
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}
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loadList() {
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// We don't render the entire list; so nothing to see here.
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}
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_removeChild(child) {
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child.root().remove();
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child.unmount();
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}
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onAdd(idx, value) {
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const {topCount, renderCount, bottomCount} = this._renderRange;
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if (this._renderRange.containsIndex(idx)) {
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this.onBeforeListChanged();
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const normalizedIdx = this._renderRange.normalize(idx);
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if (bottomCount === 0) {
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/*
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If we're at the bottom of the list, we need to render the additional item
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without removing another item from the list.
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We can't increment topCount because the index topCount is not affected by the
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add operation (and any modification will thus break ItemRange.normalize()).
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We can't increment bottomCount because there's not enough items left to trigger
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a further render.
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*/
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this._renderRange = new ItemRange(topCount, renderCount + 1, bottomCount);
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}
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else {
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// Remove the last element, render the new element
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this._removeChild(this._childInstances.pop());
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this._renderRange = new ItemRange(topCount, renderCount, bottomCount + 1);
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}
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super.onAdd(normalizedIdx, value, true);
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this.onListChanged();
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}
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else {
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this._renderRange = idx < topCount ? new ItemRange(topCount + 1, renderCount, bottomCount):
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new ItemRange(topCount, renderCount, bottomCount + 1);
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}
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this._adjustPadding(this._renderRange);
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}
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onRemove(idx, value) {
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const {topCount, renderCount, bottomCount} = this._renderRange;
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if (this._renderRange.containsIndex(idx)) {
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this.onBeforeListChanged();
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const normalizedIdx = this._renderRange.normalize(idx);
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super.onRemove(normalizedIdx, value, true);
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if (bottomCount === 0) {
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// See onAdd for explanation
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this._renderRange = new ItemRange(topCount, renderCount - 1, bottomCount);
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}
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else {
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const child = this._childCreator(this._itemAtIndex(this._renderRange.lastIndex));
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this._childInstances.push(child);
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this._root.appendChild(mountView(child, this._mountArgs));
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this._renderRange = new ItemRange(topCount, renderCount, bottomCount - 1);
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}
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this.onListChanged();
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}
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else {
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this._renderRange = idx < topCount ? new ItemRange(topCount - 1, renderCount, bottomCount):
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new ItemRange(topCount, renderCount, bottomCount - 1);
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}
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this._adjustPadding(this._renderRange);
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}
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onUpdate(idx, value, params) {
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if (this._renderRange.containsIndex(idx)) {
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const normalizedIdx = this._renderRange.normalize(idx);
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super.onUpdate(normalizedIdx, value, params);
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}
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}
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recreateItem(idx, value) {
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if (this._renderRange.containsIndex(idx)) {
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const normalizedIdx = this._renderRange.normalize(idx);
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super.recreateItem(normalizedIdx, value)
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}
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}
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/**
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* Render additional element from top or bottom to offset the outgoing element
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*/
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_renderExtraOnMove(fromIdx, toIdx) {
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const {topCount, renderCount} = this._renderRange;
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if (toIdx < fromIdx) {
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// Element is moved up the list, so render element from top boundary
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const index = topCount;
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const child = this._childCreator(this._itemAtIndex(index));
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this._childInstances.unshift(child);
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this._root.insertBefore(mountView(child, this._mountArgs), this._root.firstChild);
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}
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else {
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// Element is moved down the list, so render element from bottom boundary
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const index = topCount + renderCount - 1;
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const child = this._childCreator(this._itemAtIndex(index));
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this._childInstances.push(child);
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this._root.appendChild(mountView(child, this._mountArgs));
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}
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}
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/**
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* Remove an element from top or bottom to make space for the incoming element
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*/
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_removeElementOnMove(fromIdx, toIdx) {
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// If element comes from the bottom, remove element at bottom and vice versa
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const child = toIdx < fromIdx ? this._childInstances.pop() : this._childInstances.shift();
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this._removeChild(child);
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}
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onMove(fromIdx, toIdx, value) {
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const fromInRange = this._renderRange.containsIndex(fromIdx);
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const toInRange = this._renderRange.containsIndex(toIdx);
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const normalizedFromIdx = this._renderRange.normalize(fromIdx);
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const normalizedToIdx = this._renderRange.normalize(toIdx);
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if (fromInRange && toInRange) {
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super.onMove(normalizedFromIdx, normalizedToIdx, value);
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}
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else if (fromInRange && !toInRange) {
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this.onBeforeListChanged();
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const [child] = this._childInstances.splice(normalizedFromIdx, 1);
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this._removeChild(child);
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this._renderExtraOnMove(fromIdx, toIdx);
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this.onListChanged();
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}
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else if (!fromInRange && toInRange) {
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this.onBeforeListChanged();
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const child = this._childCreator(value);
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this._removeElementOnMove(fromIdx, toIdx);
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this._childInstances.splice(normalizedToIdx, 0, child);
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insertAt(this._root, normalizedToIdx, mountView(child, this._mountArgs));
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this.onListChanged();
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}
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}
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}
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