From f2fe81d9b55fc39e10d3c5d3aace88f0b593cd60 Mon Sep 17 00:00:00 2001
From: Alex Hart <alex@signal.org>
Date: Fri, 12 Jun 2020 17:23:40 -0300
Subject: [PATCH] Fix conversation jumping when loading at last scroll
 position.

---
 .../conversation/ConversationFragment.java    |  8 +++--
 .../conversation/ConversationViewModel.java   | 33 +++++++++++++++++--
 .../securesms/util/SnapToTopDataObserver.java |  2 --
 3 files changed, 37 insertions(+), 6 deletions(-)

diff --git a/app/src/main/java/org/thoughtcrime/securesms/conversation/ConversationFragment.java b/app/src/main/java/org/thoughtcrime/securesms/conversation/ConversationFragment.java
index 16e21c5f2f..d5a1ba1d59 100644
--- a/app/src/main/java/org/thoughtcrime/securesms/conversation/ConversationFragment.java
+++ b/app/src/main/java/org/thoughtcrime/securesms/conversation/ConversationFragment.java
@@ -424,7 +424,6 @@ public class ConversationFragment extends Fragment {
     this.threadId          = this.getActivity().getIntent().getLongExtra(ConversationActivity.THREAD_ID_EXTRA, -1);
     this.unknownSenderView = new UnknownSenderView(getActivity(), recipient.get(), threadId, () -> clearHeaderIfNotTyping(getListAdapter()));
 
-    snapToTopDataObserver.requestScrollPosition(startingPosition);
     conversationViewModel.onConversationDataAvailable(threadId, startingPosition);
 
     OnScrollListener scrollListener = new ConversationScrollListener(getActivity());
@@ -966,7 +965,12 @@ public class ConversationFragment extends Fragment {
   private void moveToMessagePosition(int position, @Nullable Runnable onMessageNotFound) {
     conversationViewModel.onConversationDataAvailable(threadId, position);
     snapToTopDataObserver.buildScrollPosition(position)
-                         .withOnScrollRequestComplete(() -> getListAdapter().pulseHighlightItem(position))
+                         .withOnPerformScroll(((layoutManager, p) ->
+                           list.post(() -> {
+                             layoutManager.scrollToPosition(p);
+                             getListAdapter().pulseHighlightItem(position);
+                           })
+                         ))
                          .withOnInvalidPosition(() -> {
                            if (onMessageNotFound != null) {
                              onMessageNotFound.run();
diff --git a/app/src/main/java/org/thoughtcrime/securesms/conversation/ConversationViewModel.java b/app/src/main/java/org/thoughtcrime/securesms/conversation/ConversationViewModel.java
index 727f0c0140..5a6cc400c0 100644
--- a/app/src/main/java/org/thoughtcrime/securesms/conversation/ConversationViewModel.java
+++ b/app/src/main/java/org/thoughtcrime/securesms/conversation/ConversationViewModel.java
@@ -17,10 +17,12 @@ import org.thoughtcrime.securesms.dependencies.ApplicationDependencies;
 import org.thoughtcrime.securesms.logging.Log;
 import org.thoughtcrime.securesms.mediasend.Media;
 import org.thoughtcrime.securesms.mediasend.MediaRepository;
+import org.thoughtcrime.securesms.util.livedata.LiveDataUtil;
 import org.thoughtcrime.securesms.util.paging.Invalidator;
 import org.whispersystems.libsignal.util.Pair;
 
 import java.util.List;
+import java.util.Objects;
 
 class ConversationViewModel extends ViewModel {
 
@@ -81,9 +83,11 @@ class ConversationViewModel extends ViewModel {
 
     this.messages = Transformations.map(messagesForThreadId, Pair::second);
 
-    LiveData<Long> distinctThread = Transformations.distinctUntilChanged(Transformations.map(messagesForThreadId, Pair::first));
+    LiveData<DistinctConversationDataByThreadId> distinctData = LiveDataUtil.combineLatest(messagesForThreadId,
+                                                                                           metadata,
+                                                                                           (m, data) -> new DistinctConversationDataByThreadId(data));
 
-    conversationMetadata = Transformations.switchMap(distinctThread, thread -> metadata);
+    conversationMetadata = Transformations.map(Transformations.distinctUntilChanged(distinctData), DistinctConversationDataByThreadId::getConversationData);
   }
 
   void onAttachmentKeyboardOpen() {
@@ -130,4 +134,29 @@ class ConversationViewModel extends ViewModel {
       return modelClass.cast(new ConversationViewModel());
     }
   }
+
+  private static class DistinctConversationDataByThreadId {
+    private final ConversationData conversationData;
+
+    private DistinctConversationDataByThreadId(@NonNull ConversationData conversationData) {
+      this.conversationData = conversationData;
+    }
+
+    public @NonNull ConversationData getConversationData() {
+      return conversationData;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+      if (this == o) return true;
+      if (o == null || getClass() != o.getClass()) return false;
+      DistinctConversationDataByThreadId that = (DistinctConversationDataByThreadId) o;
+      return Objects.equals(conversationData.getThreadId(), that.conversationData.getThreadId());
+    }
+
+    @Override
+    public int hashCode() {
+      return Objects.hash(conversationData.getThreadId());
+    }
+  }
 }
diff --git a/app/src/main/java/org/thoughtcrime/securesms/util/SnapToTopDataObserver.java b/app/src/main/java/org/thoughtcrime/securesms/util/SnapToTopDataObserver.java
index da3dd98b86..7b8039b959 100644
--- a/app/src/main/java/org/thoughtcrime/securesms/util/SnapToTopDataObserver.java
+++ b/app/src/main/java/org/thoughtcrime/securesms/util/SnapToTopDataObserver.java
@@ -77,10 +77,8 @@ public class SnapToTopDataObserver extends RecyclerView.AdapterDataObserver {
     if (!scrollRequestValidator.isPositionStillValid(position)) {
       onInvalidPosition.run();
     } else if (scrollRequestValidator.isItemAtPositionLoaded(position)) {
-      recyclerView.post(() -> {
         onPerformScroll.onPerformScroll(layoutManager, position);
         onScrollRequestComplete.run();
-      });
     } else {
       deferred.setDeferred(true);
       deferred.defer(() -> requestScrollPositionInternal(position, onPerformScroll, onScrollRequestComplete, onInvalidPosition));