131 lines
4.3 KiB
JavaScript
131 lines
4.3 KiB
JavaScript
/*
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Copyright 2020 Bruno Windels <bruno@windels.cloud>
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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 {ListView} from "../../general/ListView.js";
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import {GapView} from "./timeline/GapView.js";
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import {TextMessageView} from "./timeline/TextMessageView.js";
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import {ImageView} from "./timeline/ImageView.js";
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import {AnnouncementView} from "./timeline/AnnouncementView.js";
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export class TimelineList extends ListView {
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constructor(viewModel) {
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const options = {
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className: "Timeline",
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list: viewModel.tiles,
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}
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super(options, entry => {
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switch (entry.shape) {
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case "gap": return new GapView(entry);
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case "announcement": return new AnnouncementView(entry);
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case "message":
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case "message-status":
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return new TextMessageView(entry);
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case "image": return new ImageView(entry);
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}
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});
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this._atBottom = false;
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this._onScroll = this._onScroll.bind(this);
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this._topLoadingPromise = null;
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this._viewModel = viewModel;
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}
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async _loadAtTopWhile(predicate) {
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if (this._topLoadingPromise) {
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return;
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}
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try {
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while (predicate()) {
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// fill, not enough content to fill timeline
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this._topLoadingPromise = this._viewModel.loadAtTop();
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const shouldStop = await this._topLoadingPromise;
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if (shouldStop) {
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break;
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}
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}
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}
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catch (err) {
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//ignore error, as it is handled in the VM
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}
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finally {
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this._topLoadingPromise = null;
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}
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}
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async _onScroll() {
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const PAGINATE_OFFSET = 100;
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const root = this.root();
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if (root.scrollTop < PAGINATE_OFFSET && !this._topLoadingPromise && this._viewModel) {
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// to calculate total amountGrown to check when we stop loading
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let beforeContentHeight = root.scrollHeight;
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// to adjust scrollTop every time
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let lastContentHeight = beforeContentHeight;
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// load until pagination offset is reached again
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this._loadAtTopWhile(() => {
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const contentHeight = root.scrollHeight;
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const amountGrown = contentHeight - beforeContentHeight;
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root.scrollTop = root.scrollTop + (contentHeight - lastContentHeight);
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lastContentHeight = contentHeight;
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return amountGrown < PAGINATE_OFFSET;
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});
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}
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}
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mount() {
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const root = super.mount();
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root.addEventListener("scroll", this._onScroll);
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return root;
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}
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unmount() {
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this.root().removeEventListener("scroll", this._onScroll);
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super.unmount();
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}
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async loadList() {
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super.loadList();
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const root = this.root();
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// yield so the browser can render the list
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// and we can measure the content below
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await Promise.resolve();
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const {scrollHeight, clientHeight} = root;
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if (scrollHeight > clientHeight) {
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root.scrollTop = root.scrollHeight;
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}
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// load while viewport is not filled
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this._loadAtTopWhile(() => {
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const {scrollHeight, clientHeight} = root;
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return scrollHeight <= clientHeight;
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});
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}
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onBeforeListChanged() {
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const fromBottom = this._distanceFromBottom();
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this._atBottom = fromBottom < 1;
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}
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_distanceFromBottom() {
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const root = this.root();
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return root.scrollHeight - root.scrollTop - root.clientHeight;
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}
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onListChanged() {
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const root = this.root();
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if (this._atBottom) {
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root.scrollTop = root.scrollHeight;
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}
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}
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}
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