Fix contact search list flickering on query change.

app/src/main/java/org/thoughtcrime/securesms/contacts/ContactRepository.java

@@ -35,6 +35,7 @@ public class ContactRepository {
 
   public static final String ID_COLUMN           = "id";
   public static final String NAME_COLUMN         = "name";
+  public static final String SORT_NAME_COLUMN    = "sort_name";
          static final String NUMBER_COLUMN       = "number";
          static final String NUMBER_TYPE_COLUMN  = "number_type";
          static final String LABEL_COLUMN        = "label";
@@ -55,6 +56,11 @@ public class ContactRepository {
       return Util.getFirstNonEmpty(system, profile);
     }));
 
+    // The key the results are actually ordered by (nickname/system/profile/username, lowercased). Letter
+    // headers must derive from this rather than NAME_COLUMN, which omits nickname/username and can begin
+    // with a different letter than the row's sort position.
+    add(new Pair<>(SORT_NAME_COLUMN, cursor -> CursorUtil.requireString(cursor, RecipientTable.SORT_NAME)));
+
     add(new Pair<>(NUMBER_COLUMN, cursor -> {
       String phone = CursorUtil.requireString(cursor, RecipientTable.E164);
       String email = CursorUtil.requireString(cursor, RecipientTable.EMAIL);

app/src/main/java/org/thoughtcrime/securesms/contacts/paged/ContactSearchPagedDataSource.kt

@@ -18,7 +18,6 @@ import org.thoughtcrime.securesms.database.model.ThreadWithRecipient
 import org.thoughtcrime.securesms.keyvalue.StorySend
 import org.thoughtcrime.securesms.phonenumbers.NumberUtil
 import org.thoughtcrime.securesms.recipients.Recipient
-import org.thoughtcrime.securesms.recipients.RecipientId
 import org.thoughtcrime.securesms.search.MessageResult
 import org.thoughtcrime.securesms.search.MessageSearchResult
 import org.thoughtcrime.securesms.search.SearchRepository
@@ -240,13 +239,33 @@ class ContactSearchPagedDataSource(
     return 0
   }
 
-  private fun getNonGroupHeaderLetterMap(section: ContactSearchConfiguration.Section.Individuals, query: String?): Map<RecipientId, String> {
-    return contactSearchPagedDataSourceRepository.querySignalContactLetterHeaders(
-      query = query,
-      includeSelfMode = section.includeSelfMode,
-      includePush = true,
-      includeSms = false
-    )
+  /**
+   * Returns the letter header to display above the recipient at the cursor's current row, or null if
+   * none should be shown. A header is shown only when this row begins a new letter group, determined by
+   * comparing its letter to the immediately preceding row in display order. Peeking that single adjacent
+   * row means a letter group split across pages still yields exactly one header, anchored to the first
+   * row of the group, without re-scanning the whole contact set.
+   *
+   * The cursor is restored to its original position before returning so iteration is unaffected.
+   */
+  private fun getHeaderLetterForCurrentRow(cursor: Cursor): String? {
+    val position = cursor.position
+    val currentLetter = letterForCurrentRow(cursor) ?: return null
+
+    if (position <= 0) {
+      return currentLetter
+    }
+
+    cursor.moveToPosition(position - 1)
+    val previousLetter = letterForCurrentRow(cursor)
+    cursor.moveToPosition(position)
+
+    return if (previousLetter != currentLetter) currentLetter else null
+  }
+
+  private fun letterForCurrentRow(cursor: Cursor): String? {
+    val sortName = cursor.getString(cursor.getColumnIndexOrThrow(ContactRepository.SORT_NAME_COLUMN))
+    return sortName?.takeIf { it.isNotEmpty() }?.first()?.uppercaseChar()?.toString()
   }
 
   private fun getStoriesSearchIterator(query: String?): ContactSearchIterator<Cursor> {
@@ -379,12 +398,6 @@ class ContactSearchPagedDataSource(
   }
 
   private fun getNonGroupContactsData(section: ContactSearchConfiguration.Section.Individuals, query: String?, startIndex: Int, endIndex: Int): List<ContactSearchData> {
-    val headerMap: Map<RecipientId, String> = if (section.includeLetterHeaders) {
-      getNonGroupHeaderLetterMap(section, query)
-    } else {
-      emptyMap()
-    }
-
     return getNonGroupSearchIterator(section, query).use { records ->
       readContactData(
         records = records,
@@ -394,7 +407,8 @@ class ContactSearchPagedDataSource(
         endIndex = endIndex,
         recordMapper = {
           val recipient = contactSearchPagedDataSourceRepository.getRecipientFromSearchCursor(it)
-          ContactSearchData.KnownRecipient(section.sectionKey, recipient, headerLetter = headerMap[recipient.id])
+          val headerLetter = if (section.includeLetterHeaders) getHeaderLetterForCurrentRow(it) else null
+          ContactSearchData.KnownRecipient(section.sectionKey, recipient, headerLetter = headerLetter)
         }
       )
     }

app/src/main/java/org/thoughtcrime/securesms/contacts/paged/ContactSearchPagedDataSourceRepository.kt

@@ -43,10 +43,6 @@ open class ContactSearchPagedDataSourceRepository(
     return contactRepository.querySignalContacts(contactsSearchQuery)
   }
 
-  open fun querySignalContactLetterHeaders(query: String?, includeSelfMode: RecipientTable.IncludeSelfMode, includePush: Boolean, includeSms: Boolean): Map<RecipientId, String> {
-    return SignalDatabase.recipients.querySignalContactLetterHeaders(query ?: "", includeSelfMode, includePush, includeSms)
-  }
-
   open fun queryGroupMemberContacts(query: String?): Cursor? {
     return contactRepository.queryGroupMemberContacts(query ?: "")
   }

app/src/main/java/org/thoughtcrime/securesms/contacts/paged/ContactSearchViewModel.kt

@@ -20,7 +20,6 @@ import kotlinx.coroutines.flow.SharedFlow
 import kotlinx.coroutines.flow.SharingStarted
 import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.flow.combine
-import kotlinx.coroutines.flow.debounce
 import kotlinx.coroutines.flow.drop
 import kotlinx.coroutines.flow.flatMapLatest
 import kotlinx.coroutines.flow.flowOf
@@ -98,7 +97,7 @@ class ContactSearchViewModel(
 
   init {
     viewModelScope.launch {
-      rawQuery.drop(1).debounce(300).collect { query ->
+      rawQuery.drop(1).collect { query ->
         savedStateHandle[QUERY] = query
         internalConfigurationState.update { it.copy(query = query) }
       }
@@ -148,15 +147,17 @@ class ContactSearchViewModel(
   }
 
   suspend fun setConfiguration(contactSearchConfiguration: ContactSearchConfiguration) {
-    val pagedDataSource = ContactSearchPagedDataSource(
-      contactSearchConfiguration,
-      arbitraryRepository = arbitraryRepository,
-      searchRepository = searchRepository,
-      contactSearchPagedDataSourceRepository = contactSearchPagedDataSourceRepository
-    )
-    val size = withContext(Dispatchers.IO) { pagedDataSource.size() }
+    val (pagedDataSource, size) = withContext(Dispatchers.IO) {
+      val source = ContactSearchPagedDataSource(
+        contactSearchConfiguration,
+        arbitraryRepository = arbitraryRepository,
+        searchRepository = searchRepository,
+        contactSearchPagedDataSourceRepository = contactSearchPagedDataSourceRepository
+      )
+      source to source.size()
+    }
     internalTotalCount.value = size
-    pagedData.value = PagedData.createForStateFlow(pagedDataSource, pagingConfig)
+    pagedData.value = PagedData.createForStateFlow(pagedDataSource, pagingConfig, data.value)
   }
 
   fun setQuery(query: String?) {