From 8889261b6bf665a41aa605df77f61948a8d4b4d7 Mon Sep 17 00:00:00 2001
From: Shadowfacts <me@shadowfacts.net>
Date: Wed, 9 Jun 2021 11:01:11 -0400
Subject: [PATCH] Fix compose reply avatar scroll effect not working on iOS 15

---
 Tusker/Screens/Compose/ComposeReplyView.swift | 25 +++++++++++++------
 1 file changed, 18 insertions(+), 7 deletions(-)

diff --git a/Tusker/Screens/Compose/ComposeReplyView.swift b/Tusker/Screens/Compose/ComposeReplyView.swift
index 92ac9d70..8c984ef5 100644
--- a/Tusker/Screens/Compose/ComposeReplyView.swift
+++ b/Tusker/Screens/Compose/ComposeReplyView.swift
@@ -23,21 +23,21 @@ struct ComposeReplyView: View {
         HStack(alignment: .top, spacing: horizSpacing) {
             GeometryReader(content: self.replyAvatarImage)
                 .frame(width: 50)
-            
+
             VStack(alignment: .leading, spacing: 0) {
                 HStack {
                     AccountDisplayNameLabel(account: status.account, fontSize: 17)
                         .lineLimit(1)
                         .layoutPriority(1)
-                    
+
                     Text(verbatim: "@\(status.account.acct)")
                         .font(.system(size: 17, weight: .light))
                         .foregroundColor(.secondary)
                         .lineLimit(1)
-                    
+
                     Spacer()
                 }
-                
+
                 ComposeReplyContentView(status: status) { (newHeight) in
                     self.contentHeight = newHeight
                 }
@@ -52,9 +52,20 @@ struct ComposeReplyView: View {
     private func replyAvatarImage(geometry: GeometryProxy) -> some View {
         // using named coordinate spaces produces an incorrect scroll offset on iOS 13,
         // so simply compare the geometry inside and outside the scroll view in the global coordinate space
-        var scrollOffset = outerMinY - geometry.frame(in: .global).minY
-        scrollOffset += stackPadding
-        let offset = min(max(scrollOffset, 0), geometry.size.height - 50 - stackPadding)
+        let scrollOffset = outerMinY - geometry.frame(in: .global).minY
+        
+        // add stackPadding so that the image is always at least stackPadding away from the top
+        var offset = scrollOffset + stackPadding
+        
+        // offset can never be less than 0 (i.e., above the top of the in-reply-to content)
+        offset = max(offset, 0)
+        
+        // subtract 50, because we care about where the bottom of the view is but the offset is relative to the top of the view
+        let maxOffset = (contentHeight ?? 0) - 50
+        
+        // once you scroll past the in-reply-to-content, the bottom of the avatar should be pinned to the bottom of the content
+        offset = min(offset, maxOffset)
+        
         return ComposeAvatarImageView(url: status.account.avatar)
             .frame(width: 50, height: 50)
             .cornerRadius(preferences.avatarStyle.cornerRadiusFraction * 50)