From a79f5140b58a6cd36a8db8bebdb4b5107168822c Mon Sep 17 00:00:00 2001
From: CMK <cirno.mainasuk@gmail.com>
Date: Wed, 24 Feb 2021 17:23:01 +0800
Subject: [PATCH] feat: profile timeline scroll performance

---
 ...adMoreConfigurableTableViewContainer.swift |  7 ++++++
 .../HomeTimelineViewController.swift          | 22 +++++++------------
 2 files changed, 15 insertions(+), 14 deletions(-)

diff --git a/Mastodon/Protocol/LoadMoreConfigurableTableViewContainer.swift b/Mastodon/Protocol/LoadMoreConfigurableTableViewContainer.swift
index bc90ab1ed..4f32be54a 100644
--- a/Mastodon/Protocol/LoadMoreConfigurableTableViewContainer.swift
+++ b/Mastodon/Protocol/LoadMoreConfigurableTableViewContainer.swift
@@ -23,6 +23,13 @@ extension LoadMoreConfigurableTableViewContainer {
     func handleScrollViewDidScroll(_ scrollView: UIScrollView) {
         guard scrollView === loadMoreConfigurableTableView else { return }
 
+        // check if current scroll position is the bottom of table
+        let contentOffsetY = loadMoreConfigurableTableView.contentOffset.y
+        let bottomVisiblePageContentOffsetY = loadMoreConfigurableTableView.contentSize.height - (1.5 * loadMoreConfigurableTableView.visibleSize.height)
+        guard contentOffsetY > bottomVisiblePageContentOffsetY else {
+            return
+        }
+        
         let cells = loadMoreConfigurableTableView.visibleCells.compactMap { $0 as? BottomLoaderTableViewCell }
         guard let loaderTableViewCell = cells.first else { return }
         
diff --git a/Mastodon/Scene/HomeTimeline/HomeTimelineViewController.swift b/Mastodon/Scene/HomeTimeline/HomeTimelineViewController.swift
index 153f46130..906708fac 100644
--- a/Mastodon/Scene/HomeTimeline/HomeTimelineViewController.swift
+++ b/Mastodon/Scene/HomeTimeline/HomeTimelineViewController.swift
@@ -175,23 +175,17 @@ extension HomeTimelineViewController {
 // MARK: - UIScrollViewDelegate
 extension HomeTimelineViewController {
     func scrollViewDidScroll(_ scrollView: UIScrollView) {
-        guard scrollView === tableView else { return }
-        let cells = tableView.visibleCells.compactMap { $0 as? TimelineBottomLoaderTableViewCell }
-        guard let loaderTableViewCell = cells.first else { return }
-        
-        if let tabBar = tabBarController?.tabBar, let window = view.window {
-            let loaderTableViewCellFrameInWindow = tableView.convert(loaderTableViewCell.frame, to: nil)
-            let windowHeight = window.frame.height
-            let loaderAppear = (loaderTableViewCellFrameInWindow.origin.y + 0.8 * loaderTableViewCell.frame.height) < (windowHeight - tabBar.frame.height)
-            if loaderAppear {
-                viewModel.loadoldestStateMachine.enter(HomeTimelineViewModel.LoadOldestState.Loading.self)
-            }
-        } else {
-            viewModel.loadoldestStateMachine.enter(HomeTimelineViewModel.LoadOldestState.Loading.self)
-        }
+        handleScrollViewDidScroll(scrollView)
     }
 }
 
+extension HomeTimelineViewController: LoadMoreConfigurableTableViewContainer {
+    typealias BottomLoaderTableViewCell = TimelineBottomLoaderTableViewCell
+    typealias LoadingState = HomeTimelineViewModel.LoadOldestState.Loading
+    var loadMoreConfigurableTableView: UITableView { return tableView }
+    var loadMoreConfigurableStateMachine: GKStateMachine { return viewModel.loadoldestStateMachine }
+}
+
 // MARK: - UITableViewDelegate
 extension HomeTimelineViewController: UITableViewDelegate {