src/vs/editor/browser/viewParts/scrollDecoration/scrollDecoration.ts/ScrollDecorationViewPart/_updateWidth
class ScrollDecorationViewPart:	private _updateWidth(): void {
		const options = this._context.configuration.options;
		const layoutInfo = options.get(EditorOption.layoutInfo);

		if (layoutInfo.minimap.renderMinimap === 0 || (layoutInfo.minimap.minimapWidth > 0 && layoutInfo.minimap.minimapLeft === 0)) {
			this._width = layoutInfo.width;
		} else {
			this._width = layoutInfo.width - layoutInfo.minimap.minimapWidth - layoutInfo.verticalScrollbarWidth;
		}
	}