apple2js/js/ui/printer.ts

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import { byte } from '../types';
/**
* Printer UI. The "paper" is bound to the element selected by the input.
*
* Every line that is output to the printer is added as a <div> to the paper.
* The high bit of all characters is stripped and only visible characters are
* added to the output. The following characters receive special treatment:
*
* * `EOT` (ASCII 4): deletes last character
* * `HT` (ASCII 9): replaced with 8 spaces
* * `LF` (ASCII 10): silently removed
* * `CR` (ASCII 13): a newline and carriage return
*/
export default class Printer {
private paper: HTMLElement;
private _lineBuffer = '';
private _line: HTMLElement;
private _rawLen = 0;
private _raw = new Uint8Array(1024);
/**
* Creates a new printer bound to the given element.
* @param {string} el The selector of the element on which to bind the "paper".
*/
constructor(el: string) {
this.paper = document.querySelector(el)!;
this.newLine();
}
private newLine() {
this._line = document.createElement('div');
this._line.classList.add('line');
this._line.innerText = this._lineBuffer;
this.paper.append(this._line);
this._lineBuffer = '';
}
putChar(val: byte) {
const ascii = val & 0x7f;
const visible = val >= 0x20;
const c = String.fromCharCode(ascii);
if (c === '\r') {
this.newLine();
} else if (c === '\n') {
// eat for now
} else if (c === '\t') {
// possibly not right due to tab stops
this._lineBuffer += ' ';
} else if (ascii === 0x04) {
this._lineBuffer = this._lineBuffer.slice(0, -1);
} else if (visible) {
this._lineBuffer += c;
}
this._line.innerText = this._lineBuffer;
this._raw[this._rawLen] = val;
this._rawLen++;
if (this._rawLen > this._raw.length) {
const newRaw = new Uint8Array(this._raw.length * 2);
newRaw.set(this._raw);
this._raw = newRaw;
}
}
clear() {
this._lineBuffer = '';
this.paper.innerHTML = '';
this.newLine();
this._raw = new Uint8Array(1024);
this._rawLen = 0;
}
hasPrintout() {
return this.paper.innerText.length > 0;
}
getRawOutput() {
return this._raw.slice(0, this._rawLen);
}
}