src/vs/workbench/browser/parts/editor/sideBySideEditor.ts/SideBySideEditor/computeEditorViewState
class SideBySideEditor:	protected computeEditorViewState(resource: URI): ISideBySideEditorViewState | undefined {
		if (!this.input || !isEqual(resource, this.toEditorViewStateResource(this.input))) {
			return; // unexpected state
		}

		const primarViewState = this.primaryEditorPane?.getViewState();
		const secondaryViewState = this.secondaryEditorPane?.getViewState();

		if (!primarViewState || !secondaryViewState) {
			return; // we actually need view states
		}

		return {
			primary: primarViewState,
			secondary: secondaryViewState,
			focus: this.lastFocusedSide,
			ratio: this.getSplitViewRatio()
		};
	}