Use css variables for editor scrollbar (microsoft#165464)

Co-authored-by: gcb4 <gcb4@sfu.ca>

Author: GauravB159

src/vs/base/browser/ui/scrollbar/media/scrollbars.css

@@ -36,18 +36,33 @@
 	left: 3px;
 	height: 3px;
 	width: 100%;
+	box-shadow: var(--vscode-scrollbar-shadow) 0 6px 6px -6px inset;
 }
 .monaco-scrollable-element > .shadow.left {
 	display: block;
 	top: 3px;
 	left: 0;
 	height: 100%;
 	width: 3px;
+	box-shadow: var(--vscode-scrollbar-shadow) 6px 0 6px -6px inset;
 }
 .monaco-scrollable-element > .shadow.top-left-corner {
 	display: block;
 	top: 0;
 	left: 0;
 	height: 3px;
 	width: 3px;
+	box-shadow: var(--vscode-scrollbar-shadow) 6px 0 6px -6px inset;
+}
+
+.monaco-scrollable-element > .scrollbar > .slider {
+	background: var(--vscode-scrollbarSlider-background);
+}
+
+.monaco-scrollable-element > .scrollbar > .slider:hover {
+	background: var(--vscode-scrollbarSlider-hoverBackground);
+}
+
+.monaco-scrollable-element > .scrollbar > .slider.active {
+	background: var(--vscode-scrollbarSlider-activeBackground);
 }

src/vs/editor/browser/viewParts/editorScrollbar/editorScrollbar.ts

@@ -12,10 +12,8 @@ import { INewScrollPosition, ScrollType } from 'vs/editor/common/editorCommon';
 import { RenderingContext, RestrictedRenderingContext } from 'vs/editor/browser/view/renderingContext';
 import { ViewContext } from 'vs/editor/common/viewModel/viewContext';
 import * as viewEvents from 'vs/editor/common/viewEvents';
-import { registerThemingParticipant, getThemeTypeSelector } from 'vs/platform/theme/common/themeService';
+import { getThemeTypeSelector } from 'vs/platform/theme/common/themeService';
 import { EditorOption } from 'vs/editor/common/config/editorOptions';
-import { scrollbarShadow, scrollbarSliderActiveBackground, scrollbarSliderBackground, scrollbarSliderHoverBackground } from 'vs/platform/theme/common/colorRegistry';
-
 export class EditorScrollbar extends ViewPart {
 
 	private readonly scrollbar: SmoothScrollableElement;
@@ -180,51 +178,3 @@ export class EditorScrollbar extends ViewPart {
 		this.scrollbar.renderNow();
 	}
 }
-
-registerThemingParticipant((theme, collector) => {
-
-	// Scrollbars
-	const scrollbarShadowColor = theme.getColor(scrollbarShadow);
-	if (scrollbarShadowColor) {
-		collector.addRule(`
-			.monaco-scrollable-element > .shadow.top {
-				box-shadow: ${scrollbarShadowColor} 0 6px 6px -6px inset;
-			}
-
-			.monaco-scrollable-element > .shadow.left {
-				box-shadow: ${scrollbarShadowColor} 6px 0 6px -6px inset;
-			}
-
-			.monaco-scrollable-element > .shadow.top.left {
-				box-shadow: ${scrollbarShadowColor} 6px 6px 6px -6px inset;
-			}
-		`);
-	}
-
-	const scrollbarSliderBackgroundColor = theme.getColor(scrollbarSliderBackground);
-	if (scrollbarSliderBackgroundColor) {
-		collector.addRule(`
-			.monaco-scrollable-element > .scrollbar > .slider {
-				background: ${scrollbarSliderBackgroundColor};
-			}
-		`);
-	}
-
-	const scrollbarSliderHoverBackgroundColor = theme.getColor(scrollbarSliderHoverBackground);
-	if (scrollbarSliderHoverBackgroundColor) {
-		collector.addRule(`
-			.monaco-scrollable-element > .scrollbar > .slider:hover {
-				background: ${scrollbarSliderHoverBackgroundColor};
-			}
-		`);
-	}
-
-	const scrollbarSliderActiveBackgroundColor = theme.getColor(scrollbarSliderActiveBackground);
-	if (scrollbarSliderActiveBackgroundColor) {
-		collector.addRule(`
-			.monaco-scrollable-element > .scrollbar > .slider.active {
-				background: ${scrollbarSliderActiveBackgroundColor};
-			}
-		`);
-	}
-});