Add theme support

src/utils/CharAtlas.ts

@@ -0,0 +1,66 @@
+import { ITerminal } from '../Interfaces';
+import { IColorSet } from '../renderer/Interfaces';
+
+export function acquireCharAtlas(terminal: ITerminal, colors: IColorSet): Promise<ImageBitmap> {
+  const scaledCharWidth = terminal.charMeasure.width * window.devicePixelRatio;
+  const scaledCharHeight = terminal.charMeasure.height * window.devicePixelRatio;
+
+  // TODO: Check to see if the atlas already exists in a cache
+
+  return generator.generate(scaledCharWidth, scaledCharHeight, terminal.options.fontSize, terminal.options.fontFamily, colors.foreground, colors.ansi);
+}
+
+export function releaseCharAtlas(terminal: ITerminal): void {
+  // TODO: Release the char atlas if it's no longer needed
+}
+
+class CharAtlasGenerator {
+  private _canvas: HTMLCanvasElement;
+  private _ctx: CanvasRenderingContext2D;
+
+  constructor() {
+    this._canvas = document.createElement('canvas');
+    this._ctx = this._canvas.getContext('2d');
+    this._ctx.scale(window.devicePixelRatio, window.devicePixelRatio);
+  }
+
+  public generate(scaledCharWidth: number, scaledCharHeight: number, fontSize: number, fontFamily: string, foreground: string, ansiColors: string[]): Promise<ImageBitmap> {
+    this._canvas.width = 255 * scaledCharWidth;
+    this._canvas.height = (/*default*/1 + /*0-15*/16) * scaledCharHeight;
+
+    this._ctx.save();
+    this._ctx.fillStyle = foreground;
+    this._ctx.font = `${fontSize * window.devicePixelRatio}px ${fontFamily}`;
+    this._ctx.textBaseline = 'top';
+
+    // Default color
+    for (let i = 0; i < 256; i++) {
+      this._ctx.fillText(String.fromCharCode(i), i * scaledCharWidth, 0);
+    }
+
+    // Colors 0-15
+    for (let colorIndex = 0; colorIndex < 16; colorIndex++) {
+      // colors 8-15 are bold
+      if (colorIndex === 8) {
+        this._ctx.font = `bold ${this._ctx.font}`;
+      }
+      const y = (colorIndex + 1) * scaledCharHeight;
+      // Clear rectangle as some fonts seem to draw over the bottom boundary
+      this._ctx.clearRect(0, y, this._canvas.width, scaledCharHeight);
+      // Draw ascii characters
+      for (let i = 0; i < 256; i++) {
+        this._ctx.fillStyle = ansiColors[colorIndex];
+        this._ctx.fillText(String.fromCharCode(i), i * scaledCharWidth, y);
+      }
+    }
+    this._ctx.restore();
+
+    const charAtlasImageData = this._ctx.getImageData(0, 0, this._canvas.width, this._canvas.height);
+    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;
+  }
+}
+
+const generator = new CharAtlasGenerator();