Fix very bad performance when laying out Compose reply view

Using a non-scrolling UITextView wrapped in SwiftUI combined with the
old hack of fixing its layout by passing the view controller's width
down to the wrapped view caused very slow layouts, resulting in
significant lag when typing into the main text view of the compose
screen.

Tusker/Screens/Compose/ComposeContainerView.swift

@@ -11,24 +11,18 @@ import Combine
 
 struct ComposeContainerView: View {
     let mastodonController: MastodonController
-    let vcWidthSubject: PassthroughSubject<CGFloat, Never>
     @ObservedObject var uiState: ComposeUIState
     
     init(
         mastodonController: MastodonController,
-        vcWidthSubject: PassthroughSubject<CGFloat, Never>,
         uiState: ComposeUIState
     ) {
         self.mastodonController = mastodonController
-        self.vcWidthSubject = vcWidthSubject
         self.uiState = uiState
     }
     
     var body: some View {
-        ComposeView(
-            draft: uiState.draft,
-            vcWidthSubject: vcWidthSubject
-        )
+        ComposeView(draft: uiState.draft)
         .environmentObject(mastodonController)
         .environmentObject(uiState)
     }

Tusker/Screens/Compose/ComposeHostingController.swift

@@ -16,9 +16,6 @@ class ComposeHostingController: UIHostingController<ComposeContainerView> {
     let mastodonController: MastodonController
     
     let uiState: ComposeUIState
-    // storing the width in the UI state and having SwiftUI listen to it via @ObservedObject doesn't work
-    // it ends up spinning forever
-    let widthSubject = PassthroughSubject<CGFloat, Never>()
     
     var draft: Draft { uiState.draft }
     
@@ -42,7 +39,6 @@ class ComposeHostingController: UIHostingController<ComposeContainerView> {
         // to use as the UIHostingController type parameter
         let container = ComposeContainerView(
             mastodonController: mastodonController,
-            vcWidthSubject: widthSubject,
             uiState: uiState
         )
         super.init(rootView: container)
@@ -82,12 +78,6 @@ class ComposeHostingController: UIHostingController<ComposeContainerView> {
         fatalError("init(coder:) has not been implemented")
     }
     
-    override func viewDidLayoutSubviews() {
-        super.viewDidLayoutSubviews()
-        
-        widthSubject.send(view.bounds.width)
-    }
-    
     override func viewWillAppear(_ animated: Bool) {
         super.viewWillAppear(animated)
         

Tusker/Screens/Compose/ComposeReplyContentView.swift

@@ -12,37 +12,33 @@ struct ComposeReplyContentView: UIViewRepresentable {
     typealias UIViewType = ComposeReplyContentTextView
     
     let status: StatusMO
-    let maxWidth: CGFloat
     
     @EnvironmentObject var mastodonController: MastodonController
     
+    let heightChanged: (CGFloat) -> Void
+    
     func makeUIView(context: Context) -> ComposeReplyContentTextView {
         let view = ComposeReplyContentTextView()
         view.overrideMastodonController = mastodonController
         view.setTextFrom(status: status)
-        view.isScrollEnabled = false
         view.isUserInteractionEnabled = false
         view.backgroundColor = .clear
-        view.maxWidth = maxWidth
+        
         return view
     }
     
     func updateUIView(_ uiView: ComposeReplyContentTextView, context: Context) {
-        uiView.constraint.constant = maxWidth
+        uiView.heightChanged = heightChanged
     }
 }
 
 class ComposeReplyContentTextView: StatusContentTextView {
+    var heightChanged: ((CGFloat) -> Void)?
     
-    var maxWidth: CGFloat!
-    var constraint: NSLayoutConstraint!
+    override func layoutSubviews() {
+        super.layoutSubviews()
         
-    override func didMoveToSuperview() {
-        super.didMoveToSuperview()
-        
-        translatesAutoresizingMaskIntoConstraints = false
-        constraint = widthAnchor.constraint(lessThanOrEqualToConstant: maxWidth)
-        constraint.isActive = true
+        heightChanged?(contentSize.height)
     }
     
 }

Tusker/Screens/Compose/ComposeReplyView.swift

@@ -10,9 +10,10 @@ import SwiftUI
 
 struct ComposeReplyView: View {
     let status: StatusMO
-    let maxWidth: CGFloat
     let stackPadding: CGFloat
     
+    @State private var contentHeight: CGFloat?
+    
     private let horizSpacing: CGFloat = 8
     
     var body: some View {
@@ -35,7 +36,10 @@ struct ComposeReplyView: View {
                     Spacer()
                 }
                 
-                ComposeReplyContentView(status: status, maxWidth: maxWidth - 50 - horizSpacing + 4)
+                ComposeReplyContentView(status: status) { (newHeight) in
+                    self.contentHeight = newHeight
+                }
+                    .frame(height: contentHeight)
                     .offset(x: -4, y: -8)
                     .padding(.bottom, -8)
             }

Tusker/Screens/Compose/ComposeView.swift

@@ -12,10 +12,8 @@ import Combine
 
 struct ComposeView: View {
     @ObservedObject var draft: Draft
-    let vcWidthSubject: PassthroughSubject<CGFloat, Never>
     
     @EnvironmentObject var mastodonController: MastodonController
-    @State var viewControllerWidth: CGFloat = 0
     @EnvironmentObject var uiState: ComposeUIState
     @State var isPosting = false
     @State var postProgress: Double = 0
@@ -25,12 +23,8 @@ struct ComposeView: View {
     
     private let stackPadding: CGFloat = 8
     
-    init(
-        draft: Draft,
-        vcWidthSubject: PassthroughSubject<CGFloat, Never>
-    ) {
+    init(draft: Draft) {
         self.draft = draft
-        self.vcWidthSubject = vcWidthSubject
     }
     
     var charactersRemaining: Int {
@@ -73,7 +67,6 @@ struct ComposeView: View {
         .coordinateSpace(name: "outer")
         .onAppear(perform: self.didAppear)
         .navigationBarTitle("Compose")
-        .onReceive(vcWidthSubject) { self.viewControllerWidth = $0 }
         .actionSheet(isPresented: $uiState.isShowingSaveDraftSheet, content: self.saveAndCloseSheet)
         .alert(isPresented: $isShowingPostErrorAlert) {
             Alert(
@@ -90,7 +83,6 @@ struct ComposeView: View {
                let status = mastodonController.persistentContainer.status(for: id) {
                 ComposeReplyView(
                     status: status,
-                    maxWidth: viewControllerWidth - (2 * stackPadding),
                     stackPadding: stackPadding
                 )
             }