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fix(frontend): implement infinite scrolling for the font selection dropdown menu #17

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fix(frontend): implement infinite scrolling for the font selection dropdown menu #17

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57 changes: 44 additions & 13 deletions frontend/src/components/text-format-toolbar.tsx
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Original file line number Diff line number Diff line change
Expand Up @@ -58,9 +58,11 @@ export default function TextFormatToolbar({
const [fontQuery, setFontQuery] = useState('')
const [fontMenuOpenUpward, setFontMenuOpenUpward] = useState(false)
const [fontListMaxHeightPx, setFontListMaxHeightPx] = useState(224)
const [displayCount, setDisplayCount] = useState(LIST_LIMIT)
const rootRef = useRef<HTMLDivElement>(null)
const fontTriggerWrapRef = useRef<HTMLDivElement>(null)
const fontMenuRef = useRef<HTMLDivElement>(null)
const sentinelRef = useRef<HTMLDivElement>(null)

useEffect(() => {
if (!fontOpen) return
Expand All @@ -82,22 +84,43 @@ export default function TextFormatToolbar({
if (!fontOpen) {
setFontMenuOpenUpward(false)
setFontListMaxHeightPx(224)
setDisplayCount(LIST_LIMIT)
}
}, [fontOpen])

const filteredFonts = useMemo(() => {
useEffect(() => {
setDisplayCount(LIST_LIMIT)
}, [fontQuery])


const allFilteredFonts = useMemo(() => {
const q = fontQuery.trim().toLowerCase()
if (!q) return GOOGLE_FONT_FAMILIES.slice(0, LIST_LIMIT)
const out: string[] = []
for (const f of GOOGLE_FONT_FAMILIES) {
if (f.toLowerCase().includes(q)) {
out.push(f)
if (out.length >= LIST_LIMIT) break
}
}
return out
if (!q) return GOOGLE_FONT_FAMILIES
return GOOGLE_FONT_FAMILIES.filter((f) => f.toLowerCase().includes(q))
}, [fontQuery])

useEffect(() => {
if (!fontOpen) return
const observer = new IntersectionObserver(
(entries) => {
if (entries[0].isIntersecting) {
setDisplayCount((prev) =>
Math.min(allFilteredFonts.length, prev + LIST_LIMIT),
)
}
},
{ rootMargin: '200px' },
)
if (sentinelRef.current) observer.observe(sentinelRef.current)
return () => observer.disconnect()
}, [fontOpen, allFilteredFonts.length])
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@cubic-dev-ai cubic-dev-ai Bot Apr 28, 2026 •
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P2: IntersectionObserver effect misses sentinel remounts because displayCount is not in dependencies, which can break continued infinite loading.

Prompt for AI agents 
Check if this issue is valid — if so, understand the root cause and fix it. At frontend/src/components/text-format-toolbar.tsx, line 116:

<comment>IntersectionObserver effect misses sentinel remounts because `displayCount` is not in dependencies, which can break continued infinite loading.</comment>

<file context>
@@ -82,22 +84,43 @@ export default function TextFormatToolbar({
+    )
+    if (sentinelRef.current) observer.observe(sentinelRef.current)
+    return () => observer.disconnect()
+  }, [fontOpen, allFilteredFonts.length])
+
+
</file context>
Suggested change
}, [fontOpen, allFilteredFonts.length])
}, [fontOpen, allFilteredFonts.length, displayCount])
Fix with Cubic




const displayedFonts = useMemo(() => {
return allFilteredFonts.slice(0, displayCount)
}, [allFilteredFonts, displayCount])

useLayoutEffect(() => {
if (!fontOpen) return
if (!fontTriggerWrapRef.current) return
Expand Down Expand Up @@ -130,7 +153,7 @@ export default function TextFormatToolbar({
window.removeEventListener('resize', syncPlacement)
window.removeEventListener('scroll', syncPlacement, true)
}
}, [fontOpen, fontQuery, filteredFonts.length])
}, [fontOpen, fontQuery, displayedFonts.length])

return (
<FloatingToolbarShell
Expand Down Expand Up @@ -176,7 +199,7 @@ export default function TextFormatToolbar({
role="listbox"
aria-label="Google Fonts"
>
{filteredFonts.map((name) => (
{displayedFonts.map((name) => (
<li key={name} role="none">
<button
type="button"
Expand All @@ -196,8 +219,16 @@ export default function TextFormatToolbar({
</button>
</li>
))}
{displayCount < allFilteredFonts.length && (
<div
ref={sentinelRef}
style={{
height: (allFilteredFonts.length - displayCount) * 32,
}}
/>
)}
</ul>
{filteredFonts.length === 0 ? (
{allFilteredFonts.length === 0 ? (
<p className="px-3 py-4 text-center text-xs text-neutral-500">
No matches
</p>
Expand Down