@stringsync/vexml
Version:
MusicXML to Vexflow
46 lines (45 loc) • 1.87 kB
JavaScript
import * as util from '../util';
import { Duration } from './duration';
export class TimestampLocator {
systems;
constructor(systems) {
this.systems = systems;
}
static create(score, paths) {
const systems = score.getSystems().map((system) => {
const yRange = new util.NumberRange(system.rect().top(), system.rect().bottom());
const frames = new Array();
for (const path of paths) {
frames.push(...path
.getFrames()
.filter((frame) => frame.getActiveElements().some((element) => element.getSystemIndex() === system.getIndex())));
}
return { yRange, frames };
});
return new TimestampLocator(systems);
}
/**
* Locates the timestamp at the given point in the score. If a given point is passed multiple times within a playback
* (e.g. repeats), only the first occurrence will be returned.
*/
locate(point) {
// Let S be the number of systems and E be the number of entries in a system. The time complexity is O(S*E), but
// this is ok because we expect S and E to be small and have an upper bound of O(100).
for (const system of this.systems) {
if (!system.yRange.includes(point.y)) {
continue;
}
for (const frame of system.frames) {
if (!frame.xRange.includes(point.x)) {
continue;
}
const startMs = frame.tRange.start.ms;
const stopMs = frame.tRange.end.ms;
const alpha = (point.x - frame.xRange.start) / frame.xRange.getSize();
const timestampMs = util.lerp(startMs, stopMs, alpha);
return Duration.ms(timestampMs);
}
}
return null;
}
}