From 26c99a1a35a81d7f53689f1cc493f444a17130df Mon Sep 17 00:00:00 2001
From: Shadowfacts <me@shadowfacts.net>
Date: Sat, 25 Jan 2020 11:11:48 -0500
Subject: [PATCH] Improve scroll perform when loading new rows into table views

Instead of reloading the whole table view, only insert the rows for
statuses/notifications that were added.
---
 .../BookmarksTableViewController.swift        | 19 +++++++++------
 .../NotificationsTableViewController.swift    | 24 +++++++++++++------
 .../TimelineTableViewController.swift         | 21 ++++++++++------
 3 files changed, 43 insertions(+), 21 deletions(-)

diff --git a/Tusker/Screens/Bookmarks/BookmarksTableViewController.swift b/Tusker/Screens/Bookmarks/BookmarksTableViewController.swift
index a823ddecb2..7809209740 100644
--- a/Tusker/Screens/Bookmarks/BookmarksTableViewController.swift
+++ b/Tusker/Screens/Bookmarks/BookmarksTableViewController.swift
@@ -15,13 +15,7 @@ class BookmarksTableViewController: EnhancedTableViewController {
 
     let mastodonController: MastodonController
     
-    var statuses: [(id: String, state: StatusState)] = [] {
-        didSet {
-            DispatchQueue.main.async {
-                self.tableView.reloadData()
-            }
-        }
-    }
+    var statuses: [(id: String, state: StatusState)] = []
     
     var newer: RequestRange?
     var older: RequestRange?
@@ -55,6 +49,10 @@ class BookmarksTableViewController: EnhancedTableViewController {
             self.statuses.append(contentsOf: statuses.map { ($0.id, .unknown) })
             self.newer = pagination?.newer
             self.older = pagination?.older
+            
+            DispatchQueue.main.async {
+                self.tableView.reloadData()
+            }
         }
         
         userActivity = UserActivityManager.bookmarksActivity()
@@ -90,7 +88,14 @@ class BookmarksTableViewController: EnhancedTableViewController {
             guard case let .success(newStatuses, pagination) = response else { fatalError() }
             self.older = pagination?.older
             self.mastodonController.cache.addAll(statuses: newStatuses)
+            let newIndexPaths = (self.statuses.count..<(self.statuses.count + newStatuses.count)).map {
+                IndexPath(row: $0, section: 0)
+            }
             self.statuses.append(contentsOf: newStatuses.map { ($0.id, .unknown) })
+            
+            DispatchQueue.main.async {
+                self.tableView.insertRows(at: newIndexPaths, with: .automatic)
+            }
         }
     }
     
diff --git a/Tusker/Screens/Notifications/NotificationsTableViewController.swift b/Tusker/Screens/Notifications/NotificationsTableViewController.swift
index c76a14568b..09c22e4a95 100644
--- a/Tusker/Screens/Notifications/NotificationsTableViewController.swift
+++ b/Tusker/Screens/Notifications/NotificationsTableViewController.swift
@@ -21,13 +21,7 @@ class NotificationsTableViewController: EnhancedTableViewController {
     let excludedTypes: [Pachyderm.Notification.Kind]
     let groupTypes = [Notification.Kind.favourite, .reblog, .follow]
 
-    var groups: [NotificationGroup] = [] {
-        didSet {
-            DispatchQueue.main.async {
-                self.tableView.reloadData()
-            }
-        }
-    }
+    var groups: [NotificationGroup] = []
     
     var newer: RequestRange?
     var older: RequestRange?
@@ -73,6 +67,10 @@ class NotificationsTableViewController: EnhancedTableViewController {
             
             self.newer = pagination?.newer
             self.older = pagination?.older
+            
+            DispatchQueue.main.async {
+                self.tableView.reloadData()
+            }
         }
     }
     
@@ -133,6 +131,9 @@ class NotificationsTableViewController: EnhancedTableViewController {
                 
                 let groups = NotificationGroup.createGroups(notifications: newNotifications, only: self.groupTypes)
                 
+                let newIndexPaths = (self.groups.count..<(self.groups.count + groups.count)).map {
+                    IndexPath(row: $0, section: 0)
+                }
                 self.groups.append(contentsOf: groups)
                 
                 self.mastodonController.cache.addAll(notifications: newNotifications)
@@ -140,6 +141,10 @@ class NotificationsTableViewController: EnhancedTableViewController {
                 self.mastodonController.cache.addAll(accounts: newNotifications.map { $0.account })
 
                 self.older = pagination?.older
+                
+                DispatchQueue.main.async {
+                    self.tableView.insertRows(at: newIndexPaths, with: .automatic)
+                }
             }
         }
     }
@@ -216,6 +221,11 @@ class NotificationsTableViewController: EnhancedTableViewController {
             }
 
             DispatchQueue.main.async {
+                let newIndexPaths = (0..<groups.count).map {
+                    IndexPath(row: $0, section: 0)
+                }
+                self.tableView.insertRows(at: newIndexPaths, with: .automatic)
+                
                 self.refreshControl?.endRefreshing()
                 
                 // maintain the current position in the list (don't scroll to top)
diff --git a/Tusker/Screens/Timeline/TimelineTableViewController.swift b/Tusker/Screens/Timeline/TimelineTableViewController.swift
index 26bda5aa46..7d1267202f 100644
--- a/Tusker/Screens/Timeline/TimelineTableViewController.swift
+++ b/Tusker/Screens/Timeline/TimelineTableViewController.swift
@@ -14,13 +14,7 @@ class TimelineTableViewController: EnhancedTableViewController {
     var timeline: Timeline!
     weak var mastodonController: MastodonController!
     
-    var timelineSegments: [[(id: String, state: StatusState)]] = [] {
-        didSet {
-            DispatchQueue.main.async {
-                self.tableView.reloadData()
-            }
-        }
-    }
+    var timelineSegments: [[(id: String, state: StatusState)]] = []
     
     var newer: RequestRange?
     var older: RequestRange?
@@ -69,6 +63,9 @@ class TimelineTableViewController: EnhancedTableViewController {
             self.timelineSegments.insert(statuses.map { ($0.id, .unknown) }, at: 0)
             self.newer = pagination?.newer
             self.older = pagination?.older
+            DispatchQueue.main.async {
+                self.tableView.reloadData()
+            }
         }
     }
 
@@ -105,7 +102,12 @@ class TimelineTableViewController: EnhancedTableViewController {
                 guard case let .success(newStatuses, pagination) = response else { fatalError() }
                 self.older = pagination?.older
                 self.mastodonController.cache.addAll(statuses: newStatuses)
+                let newRows = self.timelineSegments.last!.count..<(self.timelineSegments.last!.count + newStatuses.count)
+                let newIndexPaths = newRows.map { IndexPath(row: $0, section: self.timelineSegments.count - 1) }
                 self.timelineSegments[self.timelineSegments.count - 1].append(contentsOf: newStatuses.map { ($0.id, .unknown) })
+                DispatchQueue.main.async {
+                    self.tableView.insertRows(at: newIndexPaths, with: .none)
+                }
             }
         }
     }
@@ -137,6 +139,11 @@ class TimelineTableViewController: EnhancedTableViewController {
             }
             
             DispatchQueue.main.async {
+                let newIndexPaths = (0..<newStatuses.count).map {
+                    IndexPath(row: $0, section: 0)
+                }
+                self.tableView.insertRows(at: newIndexPaths, with: .automatic)
+
                 self.refreshControl?.endRefreshing()
                 
                 // maintain the current position in the list (don't scroll to the top)