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Fix: Improve scroll lock behavior while maintaining memory efficiency #6763

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hannesrudolph wants to merge 3 commits into from
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Fix: Improve scroll lock behavior while maintaining memory efficiency #6763

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93db129
fix: improve scroll lock behavior while maintaining memory efficiency
hannesrudolph Aug 6, 2025
b38df3f
refactor: address PR review feedback
hannesrudolph Aug 6, 2025
d368697
refactor: simplify comments per review feedback
hannesrudolph Aug 6, 2025
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25 changes: 24 additions & 1 deletion webview-ui/src/components/chat/ChatView.tsx
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Original file line number Diff line number Diff line change
Expand Up @@ -70,6 +70,11 @@ export interface ChatViewRef {

export const MAX_IMAGES_PER_MESSAGE = 20 // Anthropic limits to 20 images

// Viewport buffer constants
const VIEWPORT_BUFFER_AT_BOTTOM = 10_000 // Maintains scroll lock when at bottom
const VIEWPORT_BUFFER_SCROLLED_UP = 1_000 // Reduces memory usage when scrolled up
const VIEWPORT_BUFFER_TOP = 3_000

const isMac = navigator.platform.toUpperCase().indexOf("MAC") >= 0

const ChatViewComponent: React.ForwardRefRenderFunction<ChatViewRef, ChatViewProps> = (
Expand Down Expand Up @@ -174,6 +179,8 @@ const ChatViewComponent: React.ForwardRefRenderFunction<ChatViewRef, ChatViewPro
const disableAutoScrollRef = useRef(false)
const [showScrollToBottom, setShowScrollToBottom] = useState(false)
const [isAtBottom, setIsAtBottom] = useState(false)
// Debounced version of isAtBottom to prevent rapid viewport buffer changes
const [debouncedIsAtBottom, setDebouncedIsAtBottom] = useState(false)
const lastTtsRef = useRef<string>("")
const [wasStreaming, setWasStreaming] = useState<boolean>(false)
const [showCheckpointWarning, setShowCheckpointWarning] = useState<boolean>(false)
Expand Down Expand Up @@ -1430,6 +1437,15 @@ const ChatViewComponent: React.ForwardRefRenderFunction<ChatViewRef, ChatViewPro

useEvent("wheel", handleWheel, window, { passive: true }) // passive improves scrolling performance

// Debounce isAtBottom to prevent rapid viewport buffer changes
useEffect(() => {
const timer = setTimeout(() => {
setDebouncedIsAtBottom(isAtBottom)
}, 300)

return () => clearTimeout(timer)
}, [isAtBottom])

// Effect to handle showing the checkpoint warning after a delay
useEffect(() => {
// Only show the warning when there's a task but no visible messages yet
Expand Down Expand Up @@ -1887,7 +1903,12 @@ const ChatViewComponent: React.ForwardRefRenderFunction<ChatViewRef, ChatViewPro
ref={virtuosoRef}
key={task.ts}
className="scrollable grow overflow-y-scroll mb-1"
increaseViewportBy={{ top: 3_000, bottom: 1000 }}
increaseViewportBy={{
top: VIEWPORT_BUFFER_TOP,
// Dynamic bottom buffer: larger when at bottom for scroll lock,
// smaller when scrolled up for memory efficiency
bottom: debouncedIsAtBottom ? VIEWPORT_BUFFER_AT_BOTTOM : VIEWPORT_BUFFER_SCROLLED_UP,
}}
data={groupedMessages}
itemContent={itemContent}
atBottomStateChange={(isAtBottom: boolean) => {
Expand All @@ -1899,6 +1920,8 @@ const ChatViewComponent: React.ForwardRefRenderFunction<ChatViewRef, ChatViewPro
}}
atBottomThreshold={10}
initialTopMostItemIndex={groupedMessages.length - 1}
// Smooth scrolling when new content arrives
followOutput="smooth"
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@roomote roomote bot Aug 6, 2025

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Good addition! The smooth scrolling should improve UX. Could you add a comment explaining how this relates to the scroll lock fix? This would help future maintainers understand the complete solution.

/>
</div>
<div className={`flex-initial min-h-0 ${!areButtonsVisible ? "mb-1" : ""}`}>
Expand Down
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