Create basic theme service

Part of #4184

src/browser/services/ThemeService.ts

@@ -0,0 +1,46 @@
+/**
+ * Copyright (c) 2022 The xterm.js authors. All rights reserved.
+ * @license MIT
+ */
+
+import { ColorManager } from 'browser/ColorManager';
+import { IThemeService } from 'browser/services/Services';
+import { IColorSet, ReadonlyColorSet } from 'browser/Types';
+import { Disposable } from 'common/Lifecycle';
+import { IOptionsService, ITheme } from 'common/services/Services';
+import { ColorIndex } from 'common/Types';
+
+export class ThemeService extends Disposable implements IThemeService {
+  public serviceBrand: undefined;
+
+  // TODO: Merge color manager into theme service
+  private _colorManager = new ColorManager();
+
+  public get colors(): ReadonlyColorSet { return this._colorManager.colors; }
+
+  constructor(
+    @IOptionsService private readonly _optionsService: IOptionsService
+  ) {
+    super();
+    this.register(this._optionsService.onOptionChange(key => {
+      if (key === 'theme') {
+        this.setTheme(this._optionsService.rawOptions.theme);
+      }
+      this._colorManager.handleOptionsChange(key, this._optionsService.rawOptions[key]);
+    }));
+    this._colorManager.setTheme(this._optionsService.rawOptions.theme);
+  }
+
+  public setTheme(theme: ITheme = {}): void {
+    this._colorManager.setTheme(theme);
+  }
+
+  public restoreColor(slot?: ColorIndex): void {
+    this._colorManager.restoreColor(slot);
+  }
+
+  public modifyColors(callback: (colors: IColorSet) => void): void {
+    callback(this._colorManager.colors);
+    // TODO: Fire event
+  }
+}