Created attachment 467346 [details] Scrolling freezes after scrolling horizontally inside the top bordered container on iOS/iPadOS Setup: 1. An element has a shadowRoot with a <slot> in it. 2. The element is scrollable. 3. A child element is appended and slotted to the <slot> *while* the element is scrolling. Expected: * The element continues to scroll after the child is appended. Actual: * The element immediately stops scrolling after the child is appended. Reproduction: * Scroll horizontally inside each bordered container. * Note, this issue occurs only on iOS/iPadOS. The attached reproduction shows the *incorrect* behavior when a child is appended and slotted, and it also shows the *expected* behavior when a child is appended to the shadowRoot itself rather than slotted. The reproduction is also available at https://lit.dev/playground/#gist=05deaacf5ba04c069cc41b9d523b636b&view-mode=preview.
Does this happen with equivalent DOM mutations that don't involve slots?
No, when the mutation does not involve slotting, scrolling works as expected. See the explanation of the repro at the end of the initial report.
<rdar://problem/114523840>