chore(file-viewer): trim verbose comments to match codebase style

Author: waleedlatif1

apps/sim/app/workspace/[workspaceId]/home/hooks/use-file-preview-sessions.ts

@@ -93,8 +93,6 @@ export function reduceFilePreviewSessions(
       const successor = pickActiveSessionId(nextSessions, state.activeSessionId)
       return {
         sessions: nextSessions,
-        // Preserve linger: if the active session is a completed (lingered) one
-        // and no non-complete successor exists, keep it rather than going null.
         activeSessionId: successor ?? state.activeSessionId,
       }
     }
@@ -114,10 +112,7 @@ export function reduceFilePreviewSessions(
         const successor = pickActiveSessionId(nextSessions, state.activeSessionId)
         nextActiveSessionId = successor ?? state.activeSessionId
       } else {
-        // Don't steal active from a session that already has renderable content
-        // just because a new empty/pending session arrived. Wait until the new
-        // session has actual content before switching, so the file viewer stays
-        // mounted and the user's scroll position is preserved between tool calls.
+        // Don't switch to a new session until it has renderable content — keeps the viewer mounted.
         const currentActive = state.activeSessionId ? nextSessions[state.activeSessionId] : null
         const currentHasContent = currentActive
           ? hasRenderableFilePreviewContent(currentActive)
@@ -147,11 +142,8 @@ export function reduceFilePreviewSessions(
       const successor = pickActiveSessionId(nextSessions, null)
       return {
         sessions: nextSessions,
-        // Linger on the completed session when no non-complete successor exists.
-        // This prevents a streamingContent → undefined flicker that would collapse
-        // the file viewer to shorter fetched content, clip scrollTop, and jump the
-        // user's reading position. The linger ends when a new non-complete session
-        // upserts (switching activeSessionId) or reset fires.
+        // Linger on this session until a successor upserts. Without it, streamingContent
+        // becomes undefined between tool calls, collapsing the viewer and clipping scrollTop.
         activeSessionId: successor ?? action.session.id,
       }
     }

apps/sim/hooks/use-scroll-anchor.ts

@@ -3,15 +3,8 @@ import { useCallback, useLayoutEffect, useRef } from 'react'
 const NEAR_BOTTOM_THRESHOLD = 30
 
 /**
- * Computes how much extra height the scroll-anchor spacer needs to maintain
- * the user's intended scroll position when replace-mode streaming temporarily
- * produces content shorter than that position.
- *
- * @param targetScrollTop - the scroll position the user intends to hold
- * @param clientHeight - visible height of the scroll container
- * @param scrollHeight - total scrollable height (including current spacer)
- * @param prevSpacerHeight - current spacer height (subtracted to get natural content height)
- * @returns the new `minHeight` value to apply to the spacer element, or 0 if none needed
+ * Returns the `minHeight` the spacer needs so `scrollTop` can safely reach
+ * `targetScrollTop` when replace-mode streaming produces temporarily shorter content.
  */
 export function computeSpacerShortage(
   targetScrollTop: number,
@@ -25,35 +18,22 @@ export function computeSpacerShortage(
 }
 
 /**
- * Manages scroll for a streaming content container.
- *
- * Two modes based on whether the user has ever manually scrolled:
- *
- * **Never scrolled** — auto-follows new content to the bottom while
- * streaming (MutationObserver keeps it pinned). The user can scroll up to
- * detach; scrolling back to the bottom re-engages.
+ * Manages scroll for a streaming file-preview container.
  *
- * **Has scrolled** — position is locked. The hook injects a spacer element
- * at the end of the container's content that inflates `scrollHeight` to at
- * least `intendedScrollTop + clientHeight` on every content update. This
- * prevents the browser from clamping `scrollTop` when replace-mode streaming
- * temporarily produces a chunk shorter than the previous content (which would
- * otherwise jump the viewport to the top before the content regrows).
- *
- * The "has scrolled" flag resets on unmount so each new chat / file gets a
- * clean slate (parent remounts on key change).
+ * Never-scrolled: auto-follows new content to the bottom (MutationObserver
+ * keeps it pinned). Has-scrolled: position is locked via a spacer element
+ * that inflates `scrollHeight` to prevent the browser from clamping `scrollTop`
+ * when replace-mode streaming temporarily produces a shorter chunk.
  *
  * @param isStreaming - whether the container is currently receiving streaming content
- * @param content - the current text content; drives the spacer recalculation
+ * @param content - drives spacer recalculation; pass the current text value
  */
 export function useScrollAnchor(isStreaming: boolean, content?: string) {
   const containerRef = useRef<HTMLDivElement | null>(null)
   const spacerRef = useRef<HTMLDivElement | null>(null)
   const hasUserScrolledRef = useRef(false)
   const stickyRef = useRef(false)
-
-  // The scroll position the user most recently settled on — updated only from
-  // genuine user scroll events, never from programmatic ones.
+  // Tracks the user's last intentional position; updated only on genuine user events, never programmatic ones.
   const intendedScrollTopRef = useRef(0)
 
   const scrollToBottom = useCallback(() => {
@@ -62,11 +42,9 @@ export function useScrollAnchor(isStreaming: boolean, content?: string) {
     el.scrollTop = el.scrollHeight
   }, [])
 
-  // ── event listeners ─────────────────────────────────────────────────────
-
   const onWheel = useCallback((e: WheelEvent) => {
     if (e.deltaY >= 0 || hasUserScrolledRef.current) return
-    // User scrolled up before any scroll event fired — detach immediately.
+    // Upward wheel before any scroll event fires — mark detached immediately.
     hasUserScrolledRef.current = true
     stickyRef.current = false
     const el = containerRef.current
@@ -78,25 +56,20 @@ export function useScrollAnchor(isStreaming: boolean, content?: string) {
     if (!el) return
 
     if (hasUserScrolledRef.current) {
-      // Track their position so we can restore it after a content-shrink event.
       intendedScrollTopRef.current = el.scrollTop
       return
     }
 
     const distanceFromBottom = el.scrollHeight - el.scrollTop - el.clientHeight
     if (distanceFromBottom > NEAR_BOTTOM_THRESHOLD) {
-      // User scrolled away from the bottom.
       hasUserScrolledRef.current = true
       stickyRef.current = false
       intendedScrollTopRef.current = el.scrollTop
     } else {
-      // Re-engaged (scrolled back to bottom).
       stickyRef.current = true
     }
   }, [])
 
-  // ── container ref callback ───────────────────────────────────────────────
-
   const callbackRef = useCallback(
     (el: HTMLDivElement | null) => {
       const prev = containerRef.current
@@ -113,26 +86,16 @@ export function useScrollAnchor(isStreaming: boolean, content?: string) {
     [onScroll, onWheel]
   )
 
-  // ── stream-start: decide initial pin state ───────────────────────────────
-
   useLayoutEffect(() => {
     if (!isStreaming) return
     const el = containerRef.current
     if (!el) return
-
-    if (hasUserScrolledRef.current) {
-      // User has already scrolled — never override their position.
-      return
-    }
-
-    // Fresh stream or user is at the bottom — engage sticky follow.
+    if (hasUserScrolledRef.current) return
     const distanceFromBottom = el.scrollHeight - el.scrollTop - el.clientHeight
     stickyRef.current = distanceFromBottom <= NEAR_BOTTOM_THRESHOLD
     if (stickyRef.current) scrollToBottom()
   }, [isStreaming, scrollToBottom])
 
-  // ── sticky follow: MutationObserver while streaming ──────────────────────
-
   useLayoutEffect(() => {
     if (!isStreaming) return
     const el = containerRef.current
@@ -157,39 +120,20 @@ export function useScrollAnchor(isStreaming: boolean, content?: string) {
     }
   }, [isStreaming, scrollToBottom])
 
-  // ── scroll-clip prevention via spacer ───────────────────────────────────
-  //
-  // On every content update, if the user has scrolled:
-  //   1. Compute naturalScrollHeight (container height minus spacer contribution).
-  //   2. Compute the minimum scrollHeight needed to keep intendedScrollTop valid.
-  //   3. Set spacer.minHeight to fill any gap — this inflates scrollHeight before
-  //      we read scrollTop, so the browser never clamps it to 0.
-  //   4. Restore scrollTop if it was already clipped (e.g. by prior content).
-  //
-  // When the user has NOT scrolled: clear the spacer so it doesn't interfere
-  // with auto-scroll bottom detection.
-
   useLayoutEffect(() => {
     const el = containerRef.current
     const spacer = spacerRef.current
     if (!el) return
 
-    // Clear the spacer when the user hasn't scrolled (auto-follow mode) or when
-    // streaming has ended (content is stable; no more clip-prevention needed).
     if (!hasUserScrolledRef.current || !isStreaming) {
       if (spacer) spacer.style.minHeight = '0'
       return
     }
 
-    // Capture the target BEFORE any layout read. Reading layout properties
-    // (clientHeight, scrollHeight, offsetHeight) forces a browser reflow. If
-    // scrollHeight is already smaller than scrollTop + clientHeight, the browser
-    // clamps scrollTop to 0 during that reflow and dispatches a 'scroll' event
-    // synchronously. Our onScroll handler would then overwrite intendedScrollTopRef
-    // with 0, corrupting the restore. Saving to a local variable here avoids that.
+    // Capture before any layout read: reading scrollHeight forces a reflow which can
+    // synchronously fire 'scroll' and overwrite intendedScrollTopRef with the clamped value.
     const targetScrollTop = intendedScrollTopRef.current
 
-    // Read spacer and scroll heights BEFORE mutating the spacer.
     const prevSpacerHeight = spacer ? spacer.offsetHeight : 0
     const shortage = computeSpacerShortage(
       targetScrollTop,
@@ -198,13 +142,8 @@ export function useScrollAnchor(isStreaming: boolean, content?: string) {
       prevSpacerHeight
     )
 
-    // Inflate spacer so scrollHeight >= needed, preventing scrollTop clamping.
     if (spacer) spacer.style.minHeight = `${shortage}px`
-
-    // Restore scroll position (now valid because spacer ensures enough height).
-    if (el.scrollTop < targetScrollTop) {
-      el.scrollTop = targetScrollTop
-    }
+    if (el.scrollTop < targetScrollTop) el.scrollTop = targetScrollTop
   }, [content, isStreaming])
 
   return {