Daniel Imms
98e234992b
performance.now() is faster than Date.now() as there's no need to consult the system clock. The more important part of this is that performance.now() is monotonic and is guaranteed to never to backwards.
87 lines
3.2 KiB
TypeScript
87 lines
3.2 KiB
TypeScript
/**
|
|
* Copyright (c) 2018 The xterm.js authors. All rights reserved.
|
|
* @license MIT
|
|
*/
|
|
|
|
const RENDER_DEBOUNCE_THRESHOLD_MS = 1000; // 1 Second
|
|
|
|
import { IRenderDebouncer } from 'browser/Types';
|
|
|
|
/**
|
|
* Debounces calls to update screen readers to update at most once configurable interval of time.
|
|
*/
|
|
export class TimeBasedDebouncer implements IRenderDebouncer {
|
|
private _rowStart: number | undefined;
|
|
private _rowEnd: number | undefined;
|
|
private _rowCount: number | undefined;
|
|
|
|
// The last moment that the Terminal was refreshed at
|
|
private _lastRefreshMs = 0;
|
|
// Whether a trailing refresh should be triggered due to a refresh request that was throttled
|
|
private _additionalRefreshRequested = false;
|
|
|
|
private _refreshTimeoutID: number | undefined;
|
|
|
|
constructor(
|
|
private _renderCallback: (start: number, end: number) => void,
|
|
private readonly _debounceThresholdMS = RENDER_DEBOUNCE_THRESHOLD_MS
|
|
) {
|
|
}
|
|
|
|
public dispose(): void {
|
|
if (this._refreshTimeoutID) {
|
|
clearTimeout(this._refreshTimeoutID);
|
|
}
|
|
}
|
|
|
|
public refresh(rowStart: number | undefined, rowEnd: number | undefined, rowCount: number): void {
|
|
this._rowCount = rowCount;
|
|
// Get the min/max row start/end for the arg values
|
|
rowStart = rowStart !== undefined ? rowStart : 0;
|
|
rowEnd = rowEnd !== undefined ? rowEnd : this._rowCount - 1;
|
|
// Set the properties to the updated values
|
|
this._rowStart = this._rowStart !== undefined ? Math.min(this._rowStart, rowStart) : rowStart;
|
|
this._rowEnd = this._rowEnd !== undefined ? Math.max(this._rowEnd, rowEnd) : rowEnd;
|
|
|
|
// Only refresh if the time since last refresh is above a threshold, otherwise wait for
|
|
// enough time to pass before refreshing again.
|
|
const refreshRequestTime: number = performance.now();
|
|
if (refreshRequestTime - this._lastRefreshMs >= this._debounceThresholdMS) {
|
|
// Enough time has lapsed since the last refresh; refresh immediately
|
|
this._lastRefreshMs = refreshRequestTime;
|
|
this._innerRefresh();
|
|
} else if (!this._additionalRefreshRequested) {
|
|
// This is the first additional request throttled; set up trailing refresh
|
|
const elapsed = refreshRequestTime - this._lastRefreshMs;
|
|
const waitPeriodBeforeTrailingRefresh = this._debounceThresholdMS - elapsed;
|
|
this._additionalRefreshRequested = true;
|
|
|
|
this._refreshTimeoutID = window.setTimeout(() => {
|
|
this._lastRefreshMs = performance.now();
|
|
this._innerRefresh();
|
|
this._additionalRefreshRequested = false;
|
|
this._refreshTimeoutID = undefined; // No longer need to clear the timeout
|
|
}, waitPeriodBeforeTrailingRefresh);
|
|
}
|
|
}
|
|
|
|
private _innerRefresh(): void {
|
|
// Make sure values are set
|
|
if (this._rowStart === undefined || this._rowEnd === undefined || this._rowCount === undefined) {
|
|
return;
|
|
}
|
|
|
|
// Clamp values
|
|
const start = Math.max(this._rowStart, 0);
|
|
const end = Math.min(this._rowEnd, this._rowCount - 1);
|
|
|
|
// Reset debouncer (this happens before render callback as the render could trigger it again)
|
|
this._rowStart = undefined;
|
|
this._rowEnd = undefined;
|
|
|
|
// Run render callback
|
|
this._renderCallback(start, end);
|
|
}
|
|
}
|
|
|