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/**
* Copyright (c) 2017 The xterm.js authors. All rights reserved.
* @license MIT
*/
import { Disposable } from 'common/Lifecycle';
export type ScreenDprListener = (newDevicePixelRatio?: number, oldDevicePixelRatio?: number) => void;
/**
* The screen device pixel ratio monitor allows listening for when the
* window.devicePixelRatio value changes. This is done not with polling but with
* the use of window.matchMedia to watch media queries. When the event fires,
* the listener will be reattached using a different media query to ensure that
* any further changes will register.
*
* The listener should fire on both window zoom changes and switching to a
* monitor with a different DPI.
*/
export class ScreenDprMonitor extends Disposable {
private _currentDevicePixelRatio: number = window.devicePixelRatio;
private _outerListener: ((this: MediaQueryList, ev: MediaQueryListEvent) => any) | undefined;
private _listener: ScreenDprListener | undefined;
private _resolutionMediaMatchList: MediaQueryList | undefined;
public setListener(listener: ScreenDprListener): void {
if (this._listener) {
this.clearListener();
}
this._listener = listener;
this._outerListener = () => {
if (!this._listener) {
return;
}
this._listener(window.devicePixelRatio, this._currentDevicePixelRatio);
this._updateDpr();
};
this._updateDpr();
}
public dispose(): void {
super.dispose();
this.clearListener();
}
private _updateDpr(): void {
if (!this._outerListener) {
return;
}
// Clear listeners for old DPR
this._resolutionMediaMatchList?.removeListener(this._outerListener);
// Add listeners for new DPR
this._currentDevicePixelRatio = window.devicePixelRatio;
this._resolutionMediaMatchList = window.matchMedia(`screen and (resolution: ${window.devicePixelRatio}dppx)`);
this._resolutionMediaMatchList.addListener(this._outerListener);
}
public clearListener(): void {
if (!this._resolutionMediaMatchList || !this._listener || !this._outerListener) {
return;
}
this._resolutionMediaMatchList.removeListener(this._outerListener);
this._resolutionMediaMatchList = undefined;
this._listener = undefined;
this._outerListener = undefined;
}
}
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