fix(chat): use `scrollTo` mechanism for `firstUnseenMessage`

- it ensures enough messages are loaded when `firstUnseenMessage` is not
  within the range of initially loaded messages

fixes: #10197

src/app/modules/main/chat_section/chat_content/messages/io_interface.nim

@@ -153,6 +153,9 @@ method resendChatMessage*(self: AccessInterface, messageId: string): string =
 method resetNewMessagesMarker*(self: AccessInterface) =
   raise newException(ValueError, "No implementation available")
 
+method resetAndScrollToNewMessagesMarker*(self: AccessInterface) =
+  raise newException(ValueError, "No implementation available")
+
 method markAllMessagesRead*(self: AccessInterface) =
   raise newException(ValueError, "No implementation available")
 

src/app/modules/main/chat_section/chat_content/messages/module.nim

@@ -32,6 +32,7 @@ type
     viewVariant: QVariant
     controller: Controller
     moduleLoaded: bool
+    scrollToFirstUnseenMessageWhenLoaded: bool
 
 proc newModule*(delegate: delegate_interface.AccessInterface, events: EventEmitter, sectionId: string, chatId: string,
   belongsToCommunity: bool, contactService: contact_service.Service, communityService: community_service.Service,
@@ -44,6 +45,7 @@ proc newModule*(delegate: delegate_interface.AccessInterface, events: EventEmitt
   result.controller = controller.newController(result, events, sectionId, chatId, belongsToCommunity, contactService,
   communityService, chatService, messageService, mailserversService)
   result.moduleLoaded = false
+  result.scrollToFirstUnseenMessageWhenLoaded = true
 
 # Forward declaration
 proc createChatIdentifierItem(self: Module): Item
@@ -682,6 +684,12 @@ method resendChatMessage*(self: Module, messageId: string): string =
   return self.controller.resendChatMessage(messageId)
 
 method resetNewMessagesMarker*(self: Module) =
+  self.scrollToFirstUnseenMessageWhenLoaded = false
+  self.view.setFirstUnseenMessageLoaded(false)
+  self.controller.getAsyncFirstUnseenMessageId()
+
+method resetAndScrollToNewMessagesMarker*(self: Module) =
+  self.scrollToFirstUnseenMessageWhenLoaded = true
   self.view.setFirstUnseenMessageLoaded(false)
   self.controller.getAsyncFirstUnseenMessageId()
 
@@ -723,7 +731,6 @@ proc updateItemsByAlbum(self: Module, items: var seq[Item], message: MessageDto)
 method onFirstUnseenMessageLoaded*(self: Module, messageId: string) =
   self.view.model().setFirstUnseenMessageId(messageId)
   self.view.model().resetNewMessagesMarker()
-  let index = self.view.model().findIndexForMessageId(messageId)
-  if (index != -1):
-    self.view.emitScrollToFirstUnreadMessageSignal(index)
+  if self.scrollToFirstUnseenMessageWhenLoaded:
+    self.scrollToMessage(messageId)
   self.view.setFirstUnseenMessageLoaded(true)

src/app/modules/main/chat_section/chat_content/messages/view.nim

@@ -246,7 +246,3 @@ QtObject:
   QtProperty[bool] firstUnseenMessageLoaded:
     read = getFirstUnseenMessageLoaded
     notify = firstUnseenMessageLoadedChanged
-
-  proc scrollToFirstUnreadMessage(self: View, messageIndex: int) {.signal.}
-  proc emitScrollToFirstUnreadMessageSignal*(self: View, messageIndex: int) =
-    self.scrollToFirstUnreadMessage(messageIndex)

src/app/modules/main/chat_section/chat_content/module.nim

@@ -387,7 +387,7 @@ method contactTrustStatusChanged*(self: Module, publicKey: string, isUntrustwort
   self.view.updateTrustStatus(isUntrustworthy)
 
 method onMadeActive*(self: Module) =
-  self.messagesModule.resetNewMessagesMarker()
+  self.messagesModule.resetAndScrollToNewMessagesMarker()
   self.view.setActive()
 
 method onMadeInactive*(self: Module) =

ui/app/AppLayouts/Chat/views/ChatMessagesView.qml

@@ -87,12 +87,6 @@ Item {
         function onScrollToMessage(messageIndex) {
             d.goToMessage(messageIndex)
         }
-
-        function onScrollToFirstUnreadMessage(messageIndex) {
-            if (d.isMostRecentMessageInViewport) {
-                d.goToMessage(messageIndex)
-            }
-        }
     }
 
     Connections {