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93 lines
3.5 KiB
TypeScript
93 lines
3.5 KiB
TypeScript
import shim from '@joplin/lib/shim';
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// SyncScrollMap is used for synchronous scrolling between Markdown Editor and Viewer.
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// It has the mapping information between the line numbers of a Markdown text and
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// the scroll positions (percents) of the elements in the HTML document transformed
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// from the Markdown text.
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// To see the detail of synchronous scrolling, refer the following design document.
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// https://github.com/laurent22/joplin/pull/5512#issuecomment-931277022
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export interface SyncScrollMap {
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line: number[];
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percent: number[];
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viewHeight: number;
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}
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// Map creation utility class
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export class SyncScrollMapper {
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private map_: SyncScrollMap = null;
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private refreshTimeoutId_: any = null;
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private refreshTime_ = 0;
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// Invalidates an outdated SyncScrollMap.
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// For a performance reason, too frequent refresh requests are
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// skippend and delayed. If forced is true, refreshing is immediately performed.
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public refresh(forced: boolean) {
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const elapsed = this.refreshTime_ ? Date.now() - this.refreshTime_ : 10 * 1000;
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if (!forced && (elapsed < 200 || this.refreshTimeoutId_)) {
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// to avoid too frequent recreations of a sync-scroll map.
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if (this.refreshTimeoutId_) {
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shim.clearTimeout(this.refreshTimeoutId_);
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this.refreshTimeoutId_ = null;
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}
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this.refreshTimeoutId_ = shim.setTimeout(() => {
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this.refreshTimeoutId_ = null;
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this.map_ = null;
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this.refreshTime_ = Date.now();
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}, 200);
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} else {
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this.map_ = null;
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this.refreshTime_ = Date.now();
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}
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}
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// Creates a new SyncScrollMap or reuses an existing one.
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public get(doc: Document): SyncScrollMap {
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// Returns a cached translation map between editor's scroll percenet
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// and viewer's scroll percent. Both attributes (line and percent) of
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// the returned map are sorted respectively.
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// Since creating this map is costly for each scroll event, it is cached.
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// When some update events which outdate it such as switching a note or
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// editing a note, it has to be invalidated (using refresh()),
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// and a new map will be created at a next scroll event.
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if (!doc) return null;
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const contentElement = doc.getElementById('joplin-container-content');
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if (!contentElement) return null;
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const height = Math.max(1, contentElement.scrollHeight - contentElement.clientHeight);
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if (this.map_) {
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// check whether map_ is obsolete
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if (this.map_.viewHeight === height) return this.map_;
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this.map_ = null;
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}
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// Since getBoundingClientRect() returns a relative position,
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// the offset of the origin is needed to get its aboslute position.
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const offset = doc.getElementById('rendered-md')?.getBoundingClientRect().top;
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if (!offset) return null;
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// Mapping information between editor's lines and viewer's elements is
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// embedded into elements by the renderer.
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// See also renderer/MdToHtml/rules/source_map.ts.
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const elems = doc.getElementsByClassName('maps-to-line');
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const map: SyncScrollMap = { line: [0], percent: [0], viewHeight: height };
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// Each map entry is total-ordered.
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let last = 0;
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for (let i = 0; i < elems.length; i++) {
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const top = elems[i].getBoundingClientRect().top - offset;
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const line = Number(elems[i].getAttribute('source-line'));
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const percent = Math.max(0, Math.min(1, top / height));
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if (map.line[last] < line && map.percent[last] < percent) {
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map.line.push(line);
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map.percent.push(percent);
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last += 1;
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}
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}
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if (map.percent[last] < 1) {
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map.line.push(1e10);
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map.percent.push(1);
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} else {
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map.line[last] = 1e10;
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}
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this.map_ = map;
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return map;
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}
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}
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