Feature: change font family of inline completions

src/vs/base/browser/dom.ts

@@ -927,6 +927,38 @@ export function isGlobalStylesheet(node: Node): boolean {
 	return globalStylesheets.has(node as HTMLStyleElement);
 }
 
+/**
+ * A version of createStyleSheet which has a unified API to initialize/set the style content.
+ */
+export function createStyleSheet2(): WrappedStyleElement {
+	return new WrappedStyleElement();
+}
+
+class WrappedStyleElement {
+	private _currentCssStyle = '';
+	private _styleSheet: HTMLStyleElement | undefined = undefined;
+
+	public setStyle(cssStyle: string): void {
+		if (cssStyle !== this._currentCssStyle) {
+			return;
+		}
+		this._currentCssStyle = cssStyle;
+
+		if (!this._styleSheet) {
+			this._styleSheet = createStyleSheet(mainWindow.document.head, (s) => s.innerText = cssStyle);
+		} else {
+			this._styleSheet.innerText = cssStyle;
+		}
+	}
+
+	public dispose(): void {
+		if (this._styleSheet) {
+			clearNode(this._styleSheet);
+			this._styleSheet = undefined;
+		}
+	}
+}
+
 export function createStyleSheet(container: HTMLElement = mainWindow.document.head, beforeAppend?: (style: HTMLStyleElement) => void, disposableStore?: DisposableStore): HTMLStyleElement {
 	const style = document.createElement('style');
 	style.type = 'text/css';

src/vs/editor/common/config/editorOptions.ts

@@ -3993,6 +3993,11 @@ export interface IInlineSuggestOptions {
 	 * Does not clear active inline suggestions when the editor loses focus.
 	 */
 	keepOnBlur?: boolean;
+
+	/**
+	 * Font family for inline suggestions.
+	 */
+	fontFamily?: string | 'default';
 }
 
 /**
@@ -4011,6 +4016,7 @@ class InlineEditorSuggest extends BaseEditorOption<EditorOption.inlineSuggest, I
 			showToolbar: 'onHover',
 			suppressSuggestions: false,
 			keepOnBlur: false,
+			fontFamily: 'default'
 		};
 
 		super(
@@ -4037,6 +4043,11 @@ class InlineEditorSuggest extends BaseEditorOption<EditorOption.inlineSuggest, I
 					default: defaults.suppressSuggestions,
 					description: nls.localize('inlineSuggest.suppressSuggestions', "Controls how inline suggestions interact with the suggest widget. If enabled, the suggest widget is not shown automatically when inline suggestions are available.")
 				},
+				'editor.inlineSuggest.fontFamily': {
+					type: 'string',
+					default: defaults.fontFamily,
+					description: nls.localize('inlineSuggest.fontFamily', "Controls the font family of the inline suggestions.")
+				},
 			}
 		);
 	}
@@ -4052,6 +4063,7 @@ class InlineEditorSuggest extends BaseEditorOption<EditorOption.inlineSuggest, I
 			showToolbar: stringSet(input.showToolbar, this.defaultValue.showToolbar, ['always', 'onHover', 'never']),
 			suppressSuggestions: boolean(input.suppressSuggestions, this.defaultValue.suppressSuggestions),
 			keepOnBlur: boolean(input.keepOnBlur, this.defaultValue.keepOnBlur),
+			fontFamily: EditorStringOption.string(input.fontFamily, this.defaultValue.fontFamily)
 		};
 	}
 }

src/vs/editor/contrib/inlineCompletions/browser/inlineCompletionsController.ts

@@ -3,6 +3,7 @@
  *  Licensed under the MIT License. See License.txt in the project root for license information.
  *--------------------------------------------------------------------------------------------*/
 
+import { createStyleSheet2 } from 'vs/base/browser/dom';
 import { alert } from 'vs/base/browser/ui/aria/aria';
 import { Disposable, toDisposable } from 'vs/base/common/lifecycle';
 import { ITransaction, autorun, autorunHandleChanges, constObservable, derived, disposableObservableValue, observableFromEvent, observableSignal, observableValue, transaction } from 'vs/base/common/observable';
@@ -52,6 +53,7 @@ export class InlineCompletionsController extends Disposable {
 		}
 	));
 	private readonly _enabled = observableFromEvent(this.editor.onDidChangeConfiguration, () => this.editor.getOption(EditorOption.inlineSuggest).enabled);
+	private readonly _fontFamily = observableFromEvent(this.editor.onDidChangeConfiguration, () => this.editor.getOption(EditorOption.inlineSuggest).fontFamily);
 
 	private _ghostTextWidget = this._register(this._instantiationService.createInstance(GhostTextWidget, this.editor, {
 		ghostText: this.model.map((v, reader) => /** ghostText */ v?.ghostText.read(reader)),
@@ -112,6 +114,17 @@ export class InlineCompletionsController extends Disposable {
 			});
 		}));
 
+		const styleElement = this._register(createStyleSheet2());
+		this._register(autorun(reader => {
+			const fontFamily = this._fontFamily.read(reader);
+			styleElement.setStyle(fontFamily === '' || fontFamily === 'default' ? `` : `
+.monaco-editor .ghost-text-decoration,
+.monaco-editor .ghost-text-decoration-preview,
+.monaco-editor .ghost-text {
+	font-family: ${fontFamily};
+}`);
+		}));
+
 		const getReason = (e: IModelContentChangedEvent): VersionIdChangeReason => {
 			if (e.isUndoing) { return VersionIdChangeReason.Undo; }
 			if (e.isRedoing) { return VersionIdChangeReason.Redo; }

src/vs/monaco.d.ts

@@ -4502,6 +4502,10 @@ declare namespace monaco.editor {
 		 * Does not clear active inline suggestions when the editor loses focus.
 		 */
 		keepOnBlur?: boolean;
+		/**
+		 * Font family for inline suggestions.
+		 */
+		fontFamily?: string | 'default';
 	}
 
 	export interface IBracketPairColorizationOptions {