Merge pull request #3206 from wgqqqqq/wgq/fix-short-conversation-alignment

Fix short mobile conversations aligning to bottom

Author: wgqqqqq

src/apps/mobile/android/app/src/main/kotlin/com/openbitfun/mobile/app/ui/chat/ConversationTimelineView.kt

@@ -194,7 +194,7 @@ internal fun ConversationTimelineView(
                 top = topInset,
                 bottom = if (bottomInset > 0.dp) bottomInset else 12.dp,
             ),
-            verticalArrangement = Arrangement.spacedBy(12.dp, Alignment.Bottom),
+            verticalArrangement = Arrangement.spacedBy(12.dp),
         ) {
             if (hasLeadingItem) {
                 item(key = "load-older-messages") {

src/apps/mobile/harmonyos/entry/src/main/ets/pages/components/ChatTimeline.ets

@@ -121,6 +121,13 @@ export struct ChatTimeline {
   private followedActiveTurnKey: string = '';
   private userScrollActive: boolean = false;
   private historyTouchActive: boolean = false;
+  private firstVisibleIndex: number = 0;
+  private historyRestoreKey: string = '';
+  private historyRestoreTop: number = 0;
+  private lastVisibleIndex: number = 0;
+  private historyRestoreTimer: number = 0;
+  private historyRestoreAttempts: number = 0;
+  private historyStableFrames: number = 0;
   // Whether new content should pull the viewport down with it. True until the
   // user scrolls up to read back through the transcript: at that point taking
   // the viewport away from them would be worse than letting the reply grow off
@@ -172,13 +179,15 @@ export struct ChatTimeline {
   aboutToDisappear(): void {
     RemoteLogger.info(`chat timeline disposed items=${this.timelineItems.length}`);
     this.clearFollowTimer();
+    this.cancelHistoryAnchor();
   }
 
   // A new turn means the user has just sent a message and expects to follow its
   // answer even if opening the keyboard changed the List viewport. Subsequent
   // revisions keep following only until the user deliberately scrolls away.
-  @Monitor('timelineRevision')
+  @Monitor('timelineRevision', 'historyLoading')
   onTimelineChanged(): void {
+    this.restoreHistoryAnchorIfNeeded();
     this.logTimelineProjection('revision');
     const activeTurnKey = this.activeTurnKey();
     if (activeTurnKey.length > 0 && activeTurnKey !== this.followedActiveTurnKey) {
@@ -207,6 +216,7 @@ export struct ChatTimeline {
                 if (!this.historyLoading) {
                   this.historyArrival.cancelArrival();
                   this.stickToBottom = false;
+                  this.captureHistoryAnchor();
                   this.onLoadOlder();
                 }
               })
@@ -339,19 +349,20 @@ export struct ChatTimeline {
       // contentPadding and SwiftUI's safeAreaInset.
       .contentStartOffset(this.topInset)
       .contentEndOffset(this.bottomInset)
-      // A streaming reply grows in place rather than arriving as a new item, so
-      // the bottom of the list has to be the anchor — otherwise the text the
-      // agent is writing right now renders below the fold and never comes back.
-      .stackFromEnd(true)
+      // Keep short transcripts at the content start. Active turns and explicit
+      // follow-to-bottom calls still place streaming content at the tail.
+      .stackFromEnd(false)
       // Keeps the read position when older messages are prepended above.
-      .maintainVisibleContentPosition(true)
+      .maintainVisibleContentPosition(false)
       .edgeEffect(EdgeEffect.Spring, { alwaysEnabled: true })
       .scrollBar(BarState.Off)
       .cachedCount(4)
       .onTouch((event: TouchEvent) => {
         if (event.type === TouchType.Down) {
+          if (!this.historyLoading) this.cancelHistoryAnchor();
           this.historyTouchActive = true;
           this.historyArrival.beginGesture();
+          RemoteLogger.info(`history gesture begin loading=${this.historyLoading} offset=${this.listScroller.currentOffset().yOffset}`);
         } else if (event.type === TouchType.Up || event.type === TouchType.Cancel) {
           this.historyTouchActive = false;
         }
@@ -361,6 +372,10 @@ export struct ChatTimeline {
           this.userScrollActive = true;
         }
       })
+      .onScrollIndex((start: number, end: number, _center: number) => {
+        this.firstVisibleIndex = start;
+        this.lastVisibleIndex = end;
+      })
       .onDidScroll((_scrollOffset: number, scrollState: ScrollState) => {
         if (this.listScroller.isAtEnd()) {
           this.stickToBottom = true;
@@ -465,19 +480,101 @@ export struct ChatTimeline {
   private evaluateHistoryStart(): void {
     const atStart: boolean = this.listScroller.currentOffset().yOffset <= 0;
     const readerOwnsPosition: boolean = this.historyTouchActive && this.userScrollActive;
+    if (atStart && this.historyTouchActive) {
+      RemoteLogger.info(`history start check owns=${readerOwnsPosition} loading=${this.historyLoading} hasMore=${this.hasMoreMessages} failed=${this.historyFailed}`);
+    }
     if (!this.historyArrival.arrived(atStart && readerOwnsPosition)) {
       return;
     }
     if (this.hasMoreMessages && !this.historyLoading && !this.historyFailed) {
       this.stickToBottom = false;
+      this.captureHistoryAnchor();
       this.onLoadOlder();
       return;
     }
     // A drag made while busy is consumed, not queued for after completion.
   }
 
+  private cancelHistoryAnchor(): void {
+    if (this.historyRestoreTimer !== 0) clearTimeout(this.historyRestoreTimer);
+    this.historyRestoreTimer = 0;
+    this.historyRestoreKey = '';
+    this.historyRestoreAttempts = 0;
+    this.historyStableFrames = 0;
+  }
+
+  private captureHistoryAnchor(): void {
+    const history = this.historyTimelineItems();
+    const header = this.hasMoreMessages ? 1 : 0;
+    // A page can extend the first assistant row upwards without adding rows.
+    // Preserve the lower visible row's trailing edge, not that row's changing head.
+    const index = Math.min(history.length - 1, Math.max(0, this.lastVisibleIndex - header));
+    const item = history[index];
+    if (!item) return;
+    try {
+      const rect = this.listScroller.getItemRect(index + header);
+      if (rect.height <= 0) return;
+      this.historyRestoreKey = ChatTimelineRevisionTracker.itemKey(item);
+      this.historyRestoreTop = rect.y + rect.height;
+      this.historyRestoreAttempts = 0;
+      this.historyStableFrames = 0;
+      this.clearFollowTimer();
+      this.stickToBottom = false;
+      RemoteLogger.info(
+        `history viewport capture key=${this.historyRestoreKey} index=${index} bottom=${this.historyRestoreTop} rows=${history.length}`
+      );
+    } catch (_) {
+      RemoteLogger.warn('History viewport capture unavailable');
+    }
+  }
+
+  private restoreHistoryAnchorIfNeeded(): void {
+    if (!this.historyRestoreKey || this.historyLoading || this.historyRestoreTimer !== 0) return;
+    this.historyRestoreTimer = setTimeout(() => {
+      this.historyRestoreTimer = 0;
+      const key = this.historyRestoreKey;
+      const history = this.historyTimelineItems();
+      const index = history.findIndex((item: ObservableChatTimelineItem) =>
+        ChatTimelineRevisionTracker.itemKey(item) === key);
+      if (index < 0 || this.historyFailed) {
+        this.cancelHistoryAnchor();
+        return;
+      }
+      this.historyRestoreAttempts++;
+      try {
+        const listIndex = index + (this.hasMoreMessages ? 1 : 0);
+        const rect = this.listScroller.getItemRect(listIndex);
+        if (rect.height <= 0) {
+          // Mount the identity's new virtual position before measuring it.
+          this.listScroller.scrollToIndex(listIndex, false, ScrollAlign.END);
+          this.historyStableFrames = 0;
+        } else {
+          const actual = rect.y + rect.height;
+          const delta = actual - this.historyRestoreTop;
+          RemoteLogger.info(
+            `history viewport measure key=${key} rows=${history.length} actual=${actual} expected=${this.historyRestoreTop} delta=${delta} attempt=${this.historyRestoreAttempts}`
+          );
+          if (Math.abs(delta) > 0.5) {
+            this.historyStableFrames = 0;
+            this.listScroller.scrollBy(0, delta);
+          } else {
+            this.historyStableFrames++;
+          }
+        }
+      } catch (_) {
+        this.listScroller.scrollToIndex(index + (this.hasMoreMessages ? 1 : 0), false, ScrollAlign.END);
+      }
+      if (this.historyStableFrames >= 3 || this.historyRestoreAttempts >= 30) {
+        RemoteLogger.info(`history viewport settle stable=${this.historyStableFrames} attempts=${this.historyRestoreAttempts}`);
+        this.cancelHistoryAnchor();
+      } else {
+        this.restoreHistoryAnchorIfNeeded();
+      }
+    }, 16);
+  }
+
   private requestFollowToBottom(reason: string): void {
-    if (!this.stickToBottom || this.followTimerId !== 0) {
+    if (this.historyRestoreKey || this.historyLoading || !this.stickToBottom || this.followTimerId !== 0) {
       return;
     }
     this.followTimerId = setTimeout(() => {
@@ -508,6 +605,11 @@ export struct ChatTimeline {
       source === ScrollSource.EDGE_EFFECT || source === ScrollSource.OTHER_USER_INPUT;
   }
 
+  private areaPosition(position: Object): number {
+    const value = (position as Record<string, Object>)?.y;
+    return this.areaLength(value === undefined ? 0 : value);
+  }
+
   private areaLength(value: Object): number {
     const parsed = Number.parseFloat(`${value}`);
     return Number.isNaN(parsed) ? 0 : parsed;

src/apps/mobile/harmonyos/entry/src/main/ets/pages/components/ConversationLoadingState.ets

@@ -3,6 +3,7 @@ import { LINE, SOFT } from './Theme';
 @ComponentV2
 export struct ConversationLoadingState {
   @Param maxContentWidth: number = 0;
+  @Param topInset: number = 0;
 
   build() {
     Row() {
@@ -13,7 +14,7 @@ export struct ConversationLoadingState {
       }
       .width('100%')
       .constraintSize({ maxWidth: this.maxContentWidth > 0 ? this.maxContentWidth : '100%' })
-      .padding({ left: 22, right: 22, top: 28, bottom: 28 })
+      .padding({ left: 22, right: 22, top: this.topInset + 28, bottom: 28 })
     }
     .width('100%')
     .height('100%')

src/apps/mobile/harmonyos/entry/src/main/ets/pages/components/ConversationView.ets

@@ -243,7 +243,8 @@ export struct ConversationView {
         .height('100%')
         if (this.isLoadingTranscript) {
           ConversationLoadingState({
-            maxContentWidth: this.composerPresentation === ComposerPresentation.Floating ? 760 : 0
+            maxContentWidth: this.composerPresentation === ComposerPresentation.Floating ? 760 : 0,
+            topInset: this.hoverOperateMode ? 0 : this.topInset
           })
             .width('100%')
             .height('100%')

src/apps/mobile/harmonyos/entry/src/main/ets/services/HostSessionStream.ets

@@ -1,3 +1,4 @@
+import { RemoteLogger } from './RemoteLogger';
 import { CommandStatusResponse } from '../model/RemoteModels';
 
 /** Stream id of the host's workspace/session catalog. */
@@ -257,7 +258,10 @@ export class HostSessionStream {
     let pages = 0;
     try {
       while (this.hasOlder && pages < MAX_HISTORY_PAGES_PER_REQUEST && !this.stopped) {
-        const page = await this.read({ before: this.oldest, epoch: this.epoch });
+        const before = this.oldest;
+        RemoteLogger.info(`history page request stream=${this.streamId} before=${before} epoch=${this.epoch}`);
+        const page = await this.read({ before: before, epoch: this.epoch });
+        RemoteLogger.info(`history page received stream=${this.streamId} before=${before} events=${page.events.length} first=${page.events[0]?.seq} hasMore=${page.has_more} epoch=${page.epoch}`);
         if (this.stopped) return;
         if (page.epoch !== this.epoch) {
           await this.gap();

src/crates/assembly/core/src/agentic/persistence/manager.rs

@@ -6570,11 +6570,30 @@ mod tests {
             .await
             .expect("staged revert should save");
 
+        assert!(manager
+            .load_visible_session_turn(workspace.path(), &session_id, "turn-1")
+            .await
+            .expect("hidden lookup")
+            .is_none());
         std::fs::write(
             manager.turn_path(workspace.path(), &session_id, 1),
             "invalid json",
         )
         .unwrap();
+        assert_eq!(
+            manager
+                .load_visible_session_turn(workspace.path(), &session_id, "turn-0")
+                .await
+                .expect("indexed lookup")
+                .expect("visible turn")
+                .turn_id,
+            "turn-0"
+        );
+        assert!(manager
+            .load_visible_session_turn(workspace.path(), &session_id, "unknown")
+            .await
+            .expect("missing lookup")
+            .is_none());
         let (page, next) = manager
             .load_visible_history_turn(workspace.path(), &session_id, None)
             .await