diff --git a/packages/next/src/client/components/layout-router.tsx b/packages/next/src/client/components/layout-router.tsx index d0aad92191..6878fd53f9 100644 --- a/packages/next/src/client/components/layout-router.tsx +++ b/packages/next/src/client/components/layout-router.tsx @@ -108,11 +108,45 @@ const enum ScrollTargetState { } /** - * Check where the top corner of the HTMLElement is relative to the viewport. + * Resolve the root scroll padding used by the viewport check. + * + * Computed lengths serialize as pixels, but percentages remain relative to + * the scrollport. Preserve the existing behavior for values that still + * contain unresolved CSS math. + */ +function getScrollPaddingTopInPixels( + htmlElement: HTMLElement, + viewportHeight: number +): number { + const scrollPaddingTop = getComputedStyle(htmlElement).scrollPaddingTop + const value = Number.parseFloat(scrollPaddingTop) + + if (!Number.isFinite(value) || value < 0) { + return 0 + } + + if (scrollPaddingTop.endsWith('px')) { + return value + } + + if (scrollPaddingTop.endsWith('%')) { + return (value / 100) * viewportHeight + } + + return 0 +} + +/** + * Check where the top corner of the HTMLElement is relative to the usable + * viewport. + * + * Scroll padding is resolved lazily so an empty Fragment does not trigger a + * computed style read. The caller caches the value for the second check. */ function getScrollTargetState( instance: HTMLElement | FragmentInstance, - viewportHeight: number + viewportHeight: number, + getScrollPaddingTop: () => number ): ScrollTargetState { const rects = instance.getClientRects() if (rects.length === 0) { @@ -125,7 +159,7 @@ function getScrollTargetState( elementTop = rect.top } } - return elementTop >= 0 && elementTop <= viewportHeight + return elementTop >= getScrollPaddingTop() && elementTop <= viewportHeight ? ScrollTargetState.InViewport : ScrollTargetState.OutOfViewport } @@ -226,10 +260,21 @@ class InnerScrollAndFocusHandlerOld extends React.Component { + if (scrollPaddingTop === null) { + // Reuse the style and layout update from the geometry read above. + scrollPaddingTop = getScrollPaddingTopInPixels( + htmlElement, + viewportHeight + ) + } + return scrollPaddingTop + } // If the element's top edge is already in the viewport, exit early. if ( - getScrollTargetState(domNode, viewportHeight) === + getScrollTargetState(domNode, viewportHeight, getScrollPaddingTop) === ScrollTargetState.InViewport ) { return @@ -243,7 +288,7 @@ class InnerScrollAndFocusHandlerOld extends React.Component { + if (scrollPaddingTop === null) { + // Reuse the style and layout update from the geometry read. + scrollPaddingTop = getScrollPaddingTopInPixels( + htmlElement, + viewportHeight! + ) + } + return scrollPaddingTop + } if (!hashFragment) { // Store the current viewport height because reading `clientHeight` causes a reflow, // and it won't change during this function. viewportHeight = htmlElement.clientHeight - initialTargetState = getScrollTargetState(instance, viewportHeight) + initialTargetState = getScrollTargetState( + instance, + viewportHeight, + getScrollPaddingTop + ) // An empty Fragment is not a scroll target. In particular, avoid // React's sibling fallback and leave the scroll signal available @@ -366,8 +426,11 @@ function InnerScrollHandlerNew(props: ScrollAndMaybeFocusHandlerProps) { // Scroll to domNode if domNode is not in viewport when scrolled to top of document if ( - getScrollTargetState(instance, viewportHeight!) === - ScrollTargetState.OutOfViewport + getScrollTargetState( + instance, + viewportHeight!, + getScrollPaddingTop + ) === ScrollTargetState.OutOfViewport ) { // Scroll into view doesn't scroll horizontally by default when not needed instance.scrollIntoView()