56 lines
1.8 KiB
TypeScript
56 lines
1.8 KiB
TypeScript
/**
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* Copyright (c) 2016 The xterm.js authors. All rights reserved.
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* @license MIT
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*/
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import { ICharMeasure, ITerminalOptions } from '../Types';
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import { EventEmitter } from '../common/EventEmitter';
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/**
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* Utility class that measures the size of a character. Measurements are done in
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* the DOM rather than with a canvas context because support for extracting the
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* height of characters is patchy across browsers.
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*/
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export class CharMeasure extends EventEmitter implements ICharMeasure {
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private _document: Document;
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private _parentElement: HTMLElement;
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private _measureElement: HTMLElement;
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private _width: number;
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private _height: number;
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constructor(document: Document, parentElement: HTMLElement) {
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super();
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this._document = document;
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this._parentElement = parentElement;
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this._measureElement = this._document.createElement('span');
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this._measureElement.classList.add('xterm-char-measure-element');
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this._measureElement.textContent = 'W';
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this._measureElement.setAttribute('aria-hidden', 'true');
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this._parentElement.appendChild(this._measureElement);
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}
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public get width(): number {
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return this._width;
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}
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public get height(): number {
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return this._height;
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}
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public measure(options: ITerminalOptions): void {
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this._measureElement.style.fontFamily = options.fontFamily;
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this._measureElement.style.fontSize = `${options.fontSize}px`;
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const geometry = this._measureElement.getBoundingClientRect();
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// The element is likely currently display:none, we should retain the
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// previous value.
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if (geometry.width === 0 || geometry.height === 0) {
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return;
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}
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if (this._width !== geometry.width || this._height !== geometry.height) {
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this._width = geometry.width;
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this._height = Math.ceil(geometry.height);
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this.emit('charsizechanged');
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}
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}
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}
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