Color of buttons on welcome page (fixes #19454)

src/vs/workbench/parts/welcome/page/electron-browser/welcomePage.css

@@ -228,11 +228,19 @@
 
 .vs-dark .monaco-workbench > .part.editor > .content .welcomePage .commands li button {
 	color: #828282;
-	background: #191919;
+	background: rgba(0, 0, 0, .2);
 }
 
 .vs-dark .monaco-workbench > .part.editor > .content .welcomePage .commands li button:hover {
-	background: #2a2d2e;
+	background: rgba(200, 235, 255, .072);
+}
+
+.vs-dark .monaco-workbench > .part.editor > .content .welcomePage.extra-dark .commands li button {
+	background: rgba(200, 235, 255, .042);
+}
+
+.vs-dark .monaco-workbench > .part.editor > .content .welcomePage.extra-dark .commands li button:hover {
+	background: rgba(200, 235, 255, .072);
 }
 
 .vs .monaco-workbench > .part.editor > .content .welcomePage .commands li button:focus {

src/vs/workbench/parts/welcome/page/electron-browser/welcomePage.ts

@@ -33,6 +33,9 @@ import { used } from 'vs/workbench/parts/welcome/page/electron-browser/vs_code_w
 import { ILifecycleService } from 'vs/platform/lifecycle/common/lifecycle';
 import { IDisposable, dispose } from 'vs/base/common/lifecycle';
 import { tildify } from "vs/base/common/labels";
+import { editorBackground } from 'vs/platform/theme/common/colorRegistry';
+import { Themable } from 'vs/workbench/common/theme';
+import { IThemeService, ITheme } from 'vs/platform/theme/common/themeService';
 
 used();
 
@@ -97,6 +100,28 @@ const reorderedQuickLinks = [
 	'showInteractivePlayground',
 ];
 
+class WelcomeTheming extends Themable {
+
+	constructor(
+		themeService: IThemeService,
+		private container: HTMLElement
+	) {
+		super(themeService);
+		this.update(themeService.getTheme());
+	}
+
+	protected onThemeChange(theme: ITheme): void {
+		super.onThemeChange(theme);
+		this.update(theme);
+	}
+
+	private update(theme: ITheme): void {
+		const background = theme.getColor(editorBackground);
+		const page = this.container.querySelector('.welcomePage') as HTMLElement;
+		page.classList.toggle('extra-dark', background.getLuminosity() < 0.004);
+	}
+}
+
 class WelcomePage {
 
 	private disposables: IDisposable[] = [];
@@ -115,6 +140,7 @@ class WelcomePage {
 		@IExtensionGalleryService private extensionGalleryService: IExtensionGalleryService,
 		@IExtensionManagementService private extensionManagementService: IExtensionManagementService,
 		@ILifecycleService lifecycleService: ILifecycleService,
+		@IThemeService private themeService: IThemeService,
 		@ITelemetryService private telemetryService: ITelemetryService
 	) {
 		this.disposables.push(lifecycleService.onShutdown(() => this.dispose()));
@@ -224,6 +250,8 @@ class WelcomePage {
 				}
 			};
 		}));
+
+		this.disposables.push(new WelcomeTheming(this.themeService, container));
 	}
 
 	private installKeymap(keymapName: string, keymapIdentifier: string): void {