src/vs/workbench/contrib/notebook/browser/diff/notebookDiffOverviewRuler.ts/NotebookDiffOverviewRuler/_computeOverviewViewport
class NotebookDiffOverviewRuler:	private _computeOverviewViewport(): { height: number; top: number } | null {
		const layoutInfo = this.notebookEditor.getLayoutInfo();
		if (!layoutInfo) {
			return null;
		}

		const scrollTop = this.notebookEditor.getScrollTop();
		const scrollHeight = this.notebookEditor.getScrollHeight();

		const computedAvailableSize = Math.max(0, layoutInfo.height);
		const computedRepresentableSize = Math.max(0, computedAvailableSize - 2 * 0);
		const computedRatio = scrollHeight > 0 ? (computedRepresentableSize / scrollHeight) : 0;

		const computedSliderSize = Math.max(0, Math.floor(layoutInfo.height * computedRatio));
		const computedSliderPosition = Math.floor(scrollTop * computedRatio);

		return {
			height: computedSliderSize,
			top: computedSliderPosition
		};
	}