src/vs/workbench/browser/parts/editor/sideBySideEditor.ts/SideBySideEditor/onConfigurationUpdated
class SideBySideEditor:	private onConfigurationUpdated(event: IConfigurationChangeEvent): void {
		if (event.affectsConfiguration(SideBySideEditor.SIDE_BY_SIDE_LAYOUT_SETTING)) {
			this.orientation = this.configurationService.getValue<'vertical' | 'horizontal'>(SideBySideEditor.SIDE_BY_SIDE_LAYOUT_SETTING) === 'vertical' ? Orientation.VERTICAL : Orientation.HORIZONTAL;

			// If config updated from event, re-create the split
			// editor using the new layout orientation if it was
			// already created.
			if (this.splitview) {
				this.recreateSplitview();
			}
		}
	}