src/vs/editor/contrib/find/browser/findController.ts/FindController/_start
class FindController:	protected override async _start(opts: IFindStartOptions, newState?: INewFindReplaceState): Promise<void> {
		if (!this._widget) {
			this._createFindWidget();
		}

		const selection = this._editor.getSelection();
		let updateSearchScope = false;

		switch (this._editor.getOption(EditorOption.find).autoFindInSelection) {
			case 'always':
				updateSearchScope = true;
				break;
			case 'never':
				updateSearchScope = false;
				break;
			case 'multiline': {
				const isSelectionMultipleLine = !!selection && selection.startLineNumber !== selection.endLineNumber;
				updateSearchScope = isSelectionMultipleLine;
				break;
			}
			default:
				break;
		}

		opts.updateSearchScope = opts.updateSearchScope || updateSearchScope;

		await super._start(opts, newState);

		if (this._widget) {
			if (opts.shouldFocus === FindStartFocusAction.FocusReplaceInput) {
				this._widget.focusReplaceInput();
			} else if (opts.shouldFocus === FindStartFocusAction.FocusFindInput) {
				this._widget.focusFindInput();
			}
		}
	}