Add theme key for selection (#26093)

* Add theme key for selection

Fixes #25966

* 💄

src/vs/platform/theme/common/colorRegistry.ts

@@ -134,6 +134,8 @@ export const focusBorder = registerColor('focusBorder', { dark: Color.fromHex('#
 export const contrastBorder = registerColor('contrastBorder', { light: null, dark: null, hc: '#6FC3DF' }, nls.localize('contrastBorder', "An extra border around elements to separate them from others for greater contrast."));
 export const activeContrastBorder = registerColor('contrastActiveBorder', { light: null, dark: null, hc: focusBorder }, nls.localize('activeContrastBorder', "An extra border around active elements to separate them from others for greater contrast."));
 
+export const selectionBackground = registerColor('selection.background', { light: null, dark: null, hc: null }, nls.localize('selectionBackground', "The background color of text selections in the workbench (e.g. for input fields or text areas). Note that this does not apply to selections within the editor and the terminal."));
+
 // ----- widgets
 export const widgetShadow = registerColor('widget.shadow', { dark: '#000000', light: '#A8A8A8', hc: null }, nls.localize('widgetShadow', 'Shadow color of widgets such as find/replace inside the editor.'));
 

src/vs/workbench/electron-browser/shell.ts

@@ -103,7 +103,7 @@ import 'vs/platform/opener/browser/opener.contribution';
 import { IWorkbenchThemeService } from 'vs/workbench/services/themes/common/workbenchThemeService';
 import { WorkbenchThemeService } from 'vs/workbench/services/themes/electron-browser/workbenchThemeService';
 import { registerThemingParticipant, ITheme, ICssStyleCollector } from 'vs/platform/theme/common/themeService';
-import { foreground, focusBorder, scrollbarShadow, scrollbarSliderActiveBackground, scrollbarSliderBackground, scrollbarSliderHoverBackground, listHighlightForeground } from 'vs/platform/theme/common/colorRegistry';
+import { foreground, selectionBackground, focusBorder, scrollbarShadow, scrollbarSliderActiveBackground, scrollbarSliderBackground, scrollbarSliderHoverBackground, listHighlightForeground } from 'vs/platform/theme/common/colorRegistry';
 
 /**
  * Services that we require for the Shell
@@ -529,6 +529,12 @@ registerThemingParticipant((theme: ITheme, collector: ICssStyleCollector) => {
 		collector.addRule(`.monaco-shell { color: ${windowForeground}; }`);
 	}
 
+	// Selection
+	const windowSelectionBackground = theme.getColor(selectionBackground);
+	if (windowSelectionBackground) {
+		collector.addRule(`.monaco-shell ::selection { background-color: ${windowSelectionBackground}; }`);
+	}
+
 	// List highlight
 	const listHighlightForegroundColor = theme.getColor(listHighlightForeground);
 	if (listHighlightForegroundColor) {