src/vs/editor/contrib/folding/foldingDecorations.ts/FoldingDecorationProvider/getDecorationOption
class FoldingDecorationProvider:	getDecorationOption(isCollapsed: boolean, isHidden: boolean): ModelDecorationOptions {
		if (isHidden) {
			return FoldingDecorationProvider.HIDDEN_RANGE_DECORATION;
		}
		if (isCollapsed) {
			return this.showFoldingHighlights ? FoldingDecorationProvider.COLLAPSED_HIGHLIGHTED_VISUAL_DECORATION : FoldingDecorationProvider.COLLAPSED_VISUAL_DECORATION;
		} else if (this.autoHideFoldingControls) {
			return FoldingDecorationProvider.EXPANDED_AUTO_HIDE_VISUAL_DECORATION;
		} else {
			return FoldingDecorationProvider.EXPANDED_VISUAL_DECORATION;
		}
	}