Create basic theme service

Part of #4184

src/browser/services/Services.ts

@@ -5,10 +5,11 @@
 
 import { IEvent } from 'common/EventEmitter';
 import { IRenderDimensions, IRenderer } from 'browser/renderer/shared/Types';
-import { IColorSet } from 'browser/Types';
+import { IColorSet, ReadonlyColorSet } from 'browser/Types';
 import { ISelectionRedrawRequestEvent as ISelectionRequestRedrawEvent, ISelectionRequestScrollLinesEvent } from 'browser/selection/Types';
 import { createDecorator } from 'common/services/ServiceRegistry';
-import { IDisposable } from 'common/Types';
+import { ColorIndex, IDisposable } from 'common/Types';
+import { ITheme } from 'common/services/Services';
 
 export const ICharSizeService = createDecorator<ICharSizeService>('CharSizeService');
 export interface ICharSizeService {
@@ -73,7 +74,7 @@ export interface IRenderService extends IDisposable {
   resize(cols: number, rows: number): void;
   hasRenderer(): boolean;
   setRenderer(renderer: IRenderer): void;
-  setColors(colors: IColorSet): void;
+  setColors(colors: ReadonlyColorSet): void;
   handleDevicePixelRatioChange(): void;
   handleResize(cols: number, rows: number): void;
   handleCharSizeChanged(): void;
@@ -121,3 +122,17 @@ export interface ICharacterJoinerService {
   deregister(joinerId: number): boolean;
   getJoinedCharacters(row: number): [number, number][];
 }
+
+export const IThemeService = createDecorator<IThemeService>('ThemeService');
+export interface IThemeService {
+  serviceBrand: undefined;
+
+  readonly colors: ReadonlyColorSet;
+  setTheme(theme?: ITheme): void;
+  restoreColor(slot?: ColorIndex): void;
+  /**
+   * Allows external modifying of colors in the theme, this is used instead of {@link colors} to
+   * prevent accidental writes.
+   */
+  modifyColors(callback: (colors: IColorSet) => void): void;
+}