Refactor char atlas to enable generation with worker

README.md

@@ -166,6 +166,10 @@ Xterm.js is maintained by [SourceLair](https://www.sourcelair.com/) and a few ex
 
 To contribute either code, documentation or issues to xterm.js please read the [Contributing document](CONTRIBUTING.md) beforehand. The development of xterm.js does not require any special tool. All you need is an editor that supports JavaScript/TypeScript and a browser. You will need Node.js installed locally to get all the features working in the demo.
 
+### Code structure
+
+`src/` is roughly split up into areas of functionality such as `renderer/` that handles all rendering and `utils/` which provides general utility functions. The `shared/` folder contains code that can be used from either the main thread or a web worker thread, all code inside a `shared/` folder should only ever import other code from a `shared/` folder to minimize the amount of code run what launching a web worker.
+
 ## License Agreement
 
 If you contribute code to this project, you are implicitly allowing your code to be distributed under the MIT license. You are also implicitly verifying that all code is your original work.

src/Interfaces.ts

@@ -4,9 +4,10 @@
  */
 
 import { ICharset, ILinkMatcherOptions } from './Interfaces';
-import { LinkMatcherHandler, LinkMatcherValidationCallback, LineData, FontWeight } from './Types';
+import { LinkMatcherHandler, LinkMatcherValidationCallback, LineData } from './Types';
 import { IColorSet, IRenderer } from './renderer/Interfaces';
 import { IMouseZoneManager } from './input/Interfaces';
+import { FontWeight } from './shared/Types';
 
 export interface IBrowser {
   isNode: boolean;

src/SelectionManager.ts

@@ -4,7 +4,7 @@
  */
 
 import { MouseHelper } from './utils/MouseHelper';
-import * as Browser from './utils/Browser';
+import * as Browser from './shared/utils/Browser';
 import { CharMeasure } from './utils/CharMeasure';
 import { CircularList } from './utils/CircularList';
 import { EventEmitter } from './EventEmitter';

src/Terminal.ts

@@ -35,7 +35,7 @@ import { Renderer } from './renderer/Renderer';
 import { Linkifier } from './Linkifier';
 import { SelectionManager } from './SelectionManager';
 import { CharMeasure } from './utils/CharMeasure';
-import * as Browser from './utils/Browser';
+import * as Browser from './shared/utils/Browser';
 import { MouseHelper } from './utils/MouseHelper';
 import { CHARSETS } from './Charsets';
 import { CustomKeyEventHandler, LinkMatcherHandler, LinkMatcherValidationCallback, CharData, LineData } from './Types';
@@ -44,7 +44,6 @@ import { BELL_SOUND } from './utils/Sounds';
 import { DEFAULT_ANSI_COLORS } from './renderer/ColorManager';
 import { IMouseZoneManager } from './input/Interfaces';
 import { MouseZoneManager } from './input/MouseZoneManager';
-import { initialize as initializeCharAtlas } from './renderer/CharAtlas';
 import { IRenderer } from './renderer/Interfaces';
 
 // Let it work inside Node.js for automated testing purposes.
@@ -591,8 +590,6 @@ export class Terminal extends EventEmitter implements ITerminal, IInputHandlingT
     this.document = this.parent.ownerDocument;
     this.body = <HTMLBodyElement>this.document.body;
 
-    initializeCharAtlas(this.document);
-
     // Create main element container
     this.element = this.document.createElement('div');
     this.element.classList.add('terminal');

src/Types.ts

@@ -16,5 +16,3 @@ export enum LinkHoverEventTypes {
   TOOLTIP = 'linktooltip',
   LEAVE = 'linkleave'
 }
-
-export type FontWeight = 'normal' | 'bold' | '100' | '200' | '300' | '400' | '500' | '600' | '700' | '800' | '900';

src/renderer/CharAtlas.ts

@@ -5,7 +5,8 @@
 
 import { ITerminal, ITheme } from '../Interfaces';
 import { IColorSet } from '../renderer/Interfaces';
-import { isFirefox } from '../utils/Browser';
+import { isFirefox } from '../shared/utils/Browser';
+import { generateCharAtlas, ICharAtlasRequest } from '../shared/CharAtlasGenerator';
 
 export const CHAR_ATLAS_CELL_SPACING = 1;
 
@@ -65,8 +66,28 @@ export function acquireCharAtlas(terminal: ITerminal, colors: IColorSet, scaledC
     }
   }
 
+  const canvasFactory = (width: number, height: number) => {
+    const canvas = document.createElement('canvas');
+    canvas.width = width;
+    canvas.height = height;
+    return canvas;
+  };
+
+  const charAtlasConfig: ICharAtlasRequest = {
+    scaledCharWidth,
+    scaledCharHeight,
+    fontSize: terminal.options.fontSize,
+    fontFamily: terminal.options.fontFamily,
+    fontWeight: terminal.options.fontWeight,
+    fontWeightBold: terminal.options.fontWeightBold,
+    background: colors.background,
+    foreground: colors.foreground,
+    ansiColors: colors.ansi,
+    devicePixelRatio: window.devicePixelRatio
+  };
+
   const newEntry: ICharAtlasCacheEntry = {
-    bitmap: generator.generate(scaledCharWidth, scaledCharHeight, terminal.options.fontSize, terminal.options.fontFamily, terminal.options.fontWeight, terminal.options.fontWeightBold, colors.background, colors.foreground, colors.ansi),
+    bitmap: generateCharAtlas(window, canvasFactory, charAtlasConfig),
     config: newConfig,
     ownedBy: [terminal]
   };
@@ -109,124 +130,3 @@ function configEquals(a: ICharAtlasConfig, b: ICharAtlasConfig): boolean {
       a.colors.foreground === b.colors.foreground &&
       a.colors.background === b.colors.background;
 }
-
-let generator: CharAtlasGenerator;
-
-/**
- * Initializes the char atlas generator.
- * @param document The document.
- */
-export function initialize(document: Document): void {
-  if (!generator) {
-    generator = new CharAtlasGenerator(document);
-  }
-}
-
-class CharAtlasGenerator {
-  private _canvas: HTMLCanvasElement;
-  private _ctx: CanvasRenderingContext2D;
-
-  constructor(private _document: Document) {
-    this._canvas = this._document.createElement('canvas');
-    this._ctx = this._canvas.getContext('2d', {alpha: false});
-    this._ctx.scale(window.devicePixelRatio, window.devicePixelRatio);
-  }
-
-  public generate(scaledCharWidth: number, scaledCharHeight: number, fontSize: number, fontFamily: string, fontWeight: string, fontWeightBold: string, background: string, foreground: string, ansiColors: string[]): HTMLCanvasElement | Promise<ImageBitmap> {
-    const cellWidth = scaledCharWidth + CHAR_ATLAS_CELL_SPACING;
-    const cellHeight = scaledCharHeight + CHAR_ATLAS_CELL_SPACING;
-    this._canvas.width = 255 * cellWidth;
-    this._canvas.height = (/*default+default bold*/2 + /*0-15*/16) * cellHeight;
-
-    this._ctx.fillStyle = background;
-    this._ctx.fillRect(0, 0, this._canvas.width, this._canvas.height);
-
-    this._ctx.save();
-    this._ctx.fillStyle = foreground;
-    this._ctx.font = this._getFont(fontWeight, fontSize, fontFamily);
-    this._ctx.textBaseline = 'top';
-
-    // Default color
-    for (let i = 0; i < 256; i++) {
-      this._ctx.save();
-      this._ctx.beginPath();
-      this._ctx.rect(i * cellWidth, 0, cellWidth, cellHeight);
-      this._ctx.clip();
-      this._ctx.fillText(String.fromCharCode(i), i * cellWidth, 0);
-      this._ctx.restore();
-    }
-    // Default color bold
-    this._ctx.save();
-    this._ctx.font = this._getFont(fontWeightBold, fontSize, fontFamily);
-    for (let i = 0; i < 256; i++) {
-      this._ctx.save();
-      this._ctx.beginPath();
-      this._ctx.rect(i * cellWidth, cellHeight, cellWidth, cellHeight);
-      this._ctx.clip();
-      this._ctx.fillText(String.fromCharCode(i), i * cellWidth, cellHeight);
-      this._ctx.restore();
-    }
-    this._ctx.restore();
-
-    // Colors 0-15
-    this._ctx.font = this._getFont(fontWeight, fontSize, fontFamily);
-    for (let colorIndex = 0; colorIndex < 16; colorIndex++) {
-      // colors 8-15 are bold
-      if (colorIndex === 8) {
-        this._ctx.font = this._getFont(fontWeightBold, fontSize, fontFamily);
-      }
-      const y = (colorIndex + 2) * cellHeight;
-      // Draw ascii characters
-      for (let i = 0; i < 256; i++) {
-        this._ctx.save();
-        this._ctx.beginPath();
-        this._ctx.rect(i * cellWidth, y, cellWidth, cellHeight);
-        this._ctx.clip();
-        this._ctx.fillStyle = ansiColors[colorIndex];
-        this._ctx.fillText(String.fromCharCode(i), i * cellWidth, y);
-        this._ctx.restore();
-      }
-    }
-    this._ctx.restore();
-
-    // Support is patchy for createImageBitmap at the moment, pass a canvas back
-    // if support is lacking as drawImage works there too. Firefox is also
-    // included here as ImageBitmap appears both buggy and has horrible
-    // performance (tested on v55).
-    if (!('createImageBitmap' in window) || isFirefox) {
-      // Regenerate canvas and context as they are now owned by the char atlas
-      const result = this._canvas;
-      this._canvas = this._document.createElement('canvas');
-      this._ctx = this._canvas.getContext('2d');
-      this._ctx.scale(window.devicePixelRatio, window.devicePixelRatio);
-      return result;
-    }
-
-    const charAtlasImageData = this._ctx.getImageData(0, 0, this._canvas.width, this._canvas.height);
-
-    // Remove the background color from the image so characters may overlap
-    const r = parseInt(background.substr(1, 2), 16);
-    const g = parseInt(background.substr(3, 2), 16);
-    const b = parseInt(background.substr(5, 2), 16);
-    this._clearColor(charAtlasImageData, r, g, b);
-
-    const promise = window.createImageBitmap(charAtlasImageData);
-    // Clear the rect while the promise is in progress
-    this._ctx.clearRect(0, 0, this._canvas.width, this._canvas.height);
-    return promise;
-  }
-
-  private _clearColor(imageData: ImageData, r: number, g: number, b: number): void {
-    for (let offset = 0; offset < imageData.data.length; offset += 4) {
-      if (imageData.data[offset] === r &&
-          imageData.data[offset + 1] === g &&
-          imageData.data[offset + 2] === b) {
-        imageData.data[offset + 3] = 0;
-      }
-    }
-  }
-
-  private _getFont(fontWeight: string, fontSize: number, fontFamily: string): string {
-    return `${fontWeight} ${fontSize * window.devicePixelRatio}px ${fontFamily}`;
-  }
-}

src/shared/CharAtlasGenerator.ts

@@ -0,0 +1,140 @@
+/**
+ * Copyright (c) 2018 The xterm.js authors. All rights reserved.
+ * @license MIT
+ */
+
+import { isFirefox } from './utils/Browser';
+import { FontWeight } from './Types';
+
+declare const Promise: any;
+
+export interface IOffscreenCanvas {
+  width: number;
+  height: number;
+  getContext(type: '2d', config?: Canvas2DContextAttributes): CanvasRenderingContext2D;
+  transferToImageBitmap(): ImageBitmap;
+}
+
+export interface ICharAtlasRequest {
+  scaledCharWidth: number;
+  scaledCharHeight: number;
+  fontSize: number;
+  fontFamily: string;
+  fontWeight: FontWeight;
+  fontWeightBold: FontWeight;
+  background: string;
+  foreground: string;
+  ansiColors: string[];
+  devicePixelRatio: number;
+}
+
+export const CHAR_ATLAS_CELL_SPACING = 1;
+
+/**
+ * Generates a char atlas.
+ * @param context The window or worker context.
+ * @param canvasFactory A function to generate a canvas with a width or height.
+ * @param request The config for the new char atlas.
+ */
+export function generateCharAtlas(context: Window, canvasFactory: (width: number, height: number) => HTMLCanvasElement | IOffscreenCanvas, request: ICharAtlasRequest): HTMLCanvasElement | Promise<ImageBitmap> {
+  const cellWidth = request.scaledCharWidth + CHAR_ATLAS_CELL_SPACING;
+  const cellHeight = request.scaledCharHeight + CHAR_ATLAS_CELL_SPACING;
+  const canvas = canvasFactory(
+    /*255 ascii chars*/255 * cellWidth,
+    (/*default+default bold*/2 + /*0-15*/16) * cellHeight
+  );
+  const ctx = canvas.getContext('2d', {alpha: false});
+
+  ctx.fillStyle = request.background;
+  ctx.fillRect(0, 0, canvas.width, canvas.height);
+
+  ctx.save();
+  ctx.fillStyle = request.foreground;
+  ctx.font = getFont(request.fontWeight, request);
+  ctx.textBaseline = 'top';
+
+  // Default color
+  for (let i = 0; i < 256; i++) {
+    ctx.save();
+    ctx.beginPath();
+    ctx.rect(i * cellWidth, 0, cellWidth, cellHeight);
+    ctx.clip();
+    ctx.fillText(String.fromCharCode(i), i * cellWidth, 0);
+    ctx.restore();
+  }
+  // Default color bold
+  ctx.save();
+  ctx.font = getFont(request.fontWeightBold, request);
+  for (let i = 0; i < 256; i++) {
+    ctx.save();
+    ctx.beginPath();
+    ctx.rect(i * cellWidth, cellHeight, cellWidth, cellHeight);
+    ctx.clip();
+    ctx.fillText(String.fromCharCode(i), i * cellWidth, cellHeight);
+    ctx.restore();
+  }
+  ctx.restore();
+
+  // Colors 0-15
+  ctx.font = getFont(request.fontWeight, request);
+  for (let colorIndex = 0; colorIndex < 16; colorIndex++) {
+    // colors 8-15 are bold
+    if (colorIndex === 8) {
+      ctx.font = getFont(request.fontWeightBold, request);
+    }
+    const y = (colorIndex + 2) * cellHeight;
+    // Draw ascii characters
+    for (let i = 0; i < 256; i++) {
+      ctx.save();
+      ctx.beginPath();
+      ctx.rect(i * cellWidth, y, cellWidth, cellHeight);
+      ctx.clip();
+      ctx.fillStyle = request.ansiColors[colorIndex];
+      ctx.fillText(String.fromCharCode(i), i * cellWidth, y);
+      ctx.restore();
+    }
+  }
+  ctx.restore();
+
+  // Support is patchy for createImageBitmap at the moment, pass a canvas back
+  // if support is lacking as drawImage works there too. Firefox is also
+  // included here as ImageBitmap appears both buggy and has horrible
+  // performance (tested on v55).
+  if (!('createImageBitmap' in context) || isFirefox) {
+    // Don't attempt to clear background colors if createImageBitmap is not supported
+    if (canvas instanceof HTMLCanvasElement) {
+      // Just return the HTMLCanvas if it's a HTMLCanvasElement
+      return canvas;
+    } else {
+      // Transfer to an ImageBitmap is this is an OffscreenCanvas
+      return new Promise(r => r(canvas.transferToImageBitmap()));
+    }
+  }
+
+  const charAtlasImageData = ctx.getImageData(0, 0, canvas.width, canvas.height);
+
+  // Remove the background color from the image so characters may overlap
+  const r = parseInt(request.background.substr(1, 2), 16);
+  const g = parseInt(request.background.substr(3, 2), 16);
+  const b = parseInt(request.background.substr(5, 2), 16);
+  clearColor(charAtlasImageData, r, g, b);
+
+  return context.createImageBitmap(charAtlasImageData);
+}
+
+/**
+ * Makes a partiicular rgb color in an ImageData completely transparent.
+ */
+function clearColor(imageData: ImageData, r: number, g: number, b: number): void {
+  for (let offset = 0; offset < imageData.data.length; offset += 4) {
+    if (imageData.data[offset] === r &&
+        imageData.data[offset + 1] === g &&
+        imageData.data[offset + 2] === b) {
+      imageData.data[offset + 3] = 0;
+    }
+  }
+}
+
+function getFont(fontWeight: FontWeight, request: ICharAtlasRequest): string {
+  return `${fontWeight} ${request.fontSize * request.devicePixelRatio}px ${request.fontFamily}`;
+}

src/shared/Types.ts

@@ -0,0 +1,6 @@
+/**
+ * Copyright (c) 2018 The xterm.js authors. All rights reserved.
+ * @license MIT
+ */
+
+ export type FontWeight = 'normal' | 'bold' | '100' | '200' | '300' | '400' | '500' | '600' | '700' | '800' | '900';

src/utils/Browser.ts → src/shared/utils/Browser.ts

@@ -3,8 +3,6 @@
  * @license MIT
  */
 
-import { contains } from './Generic';
-
 const isNode = (typeof navigator === 'undefined') ? true : false;
 const userAgent = (isNode) ? 'node' : navigator.userAgent;
 const platform = (isNode) ? 'node' : navigator.platform;
@@ -20,3 +18,12 @@ export const isIpad = platform === 'iPad';
 export const isIphone = platform === 'iPhone';
 export const isMSWindows = contains(['Windows', 'Win16', 'Win32', 'WinCE'], platform);
 export const isLinux = platform.indexOf('Linux') >= 0;
+
+/**
+ * Return if the given array contains the given element
+ * @param {Array} array The array to search for the given element.
+ * @param {Object} el The element to look for into the array
+ */
+export function contains(arr: any[], el: any): boolean {
+  return arr.indexOf(el) >= 0;
+};