Eliminate popping when scrolling

This commit makes a few changes:

- Link preview views are no longer cached, only the metadata. This fixes
  a memory leak when preview videos. It will keep playing the video
  forever eventually leading to a crash. This is fixed!

- Cache the intrinsic height of previews, when loading notes it looks
  for the cached height so that things don't pop-in after the fact

- Note artifacts and previews are set in the constructor instead of
  onAppear, this prevents the size from changing and popping after it
  has been loaded into the lazyvstack

Changelog-Fixed: Fix memory leak with inline videos
Changelog-Fixed: Eliminate popping when scrolling

damus.xcodeproj/project.pbxproj

@@ -1649,7 +1649,7 @@
 				CLANG_ENABLE_MODULES = YES;
 				CODE_SIGN_ENTITLEMENTS = damus/damus.entitlements;
 				CODE_SIGN_STYLE = Automatic;
-				CURRENT_PROJECT_VERSION = 3;
+				CURRENT_PROJECT_VERSION = 7;
 				DEVELOPMENT_ASSET_PATHS = "\"damus/Preview Content\"";
 				DEVELOPMENT_TEAM = XK7H4JAB3D;
 				ENABLE_PREVIEWS = YES;
@@ -1691,7 +1691,7 @@
 				CLANG_ENABLE_MODULES = YES;
 				CODE_SIGN_ENTITLEMENTS = damus/damus.entitlements;
 				CODE_SIGN_STYLE = Automatic;
-				CURRENT_PROJECT_VERSION = 3;
+				CURRENT_PROJECT_VERSION = 7;
 				DEVELOPMENT_ASSET_PATHS = "\"damus/Preview Content\"";
 				DEVELOPMENT_TEAM = XK7H4JAB3D;
 				ENABLE_PREVIEWS = YES;

damus/Util/LinkView.swift

@@ -10,10 +10,11 @@ import LinkPresentation
 
 class CustomLinkView: LPLinkView {
     override var intrinsicContentSize: CGSize { CGSize(width: 0, height: super.intrinsicContentSize.height) }
+    
 }
 
 enum Metadata {
-    case linkmeta(LPLinkMetadata)
+    case linkmeta(CachedMetadata)
     case url(URL)
 }
 
@@ -26,12 +27,19 @@ struct LinkViewRepresentable: UIViewRepresentable {
     func makeUIView(context: Context) -> CustomLinkView {
         switch meta {
         case .linkmeta(let linkmeta):
-            return CustomLinkView(metadata: linkmeta)
+            return CustomLinkView(metadata: linkmeta.meta)
         case .url(let url):
             return CustomLinkView(url: url)
         }
     }
  
     func updateUIView(_ uiView: CustomLinkView, context: Context) {
+        switch meta {
+        case .linkmeta(let cached):
+            cached.intrinsic_height = uiView.intrinsicContentSize.height
+        case .url:
+            return
+        }
+        
     }
 }

damus/Util/PreviewCache.swift

@@ -8,8 +8,18 @@
 import Foundation
 import LinkPresentation
 
+class CachedMetadata {
+    let meta: LPLinkMetadata
+    var intrinsic_height: CGFloat?
+    
+    init(meta: LPLinkMetadata) {
+        self.meta = meta
+        self.intrinsic_height = nil
+    }
+}
+
 enum Preview {
-    case value(LinkViewRepresentable)
+    case value(CachedMetadata)
     case failed
 }
 
@@ -20,12 +30,12 @@ class PreviewCache {
         return previews[evid]
     }
     
-    func store(evid: String, preview: LinkViewRepresentable?)  {
+    func store(evid: String, preview: LPLinkMetadata?)  {
         switch preview {
         case .none:
             previews[evid] = .failed
         case .some(let meta):
-            previews[evid] = .value(meta)
+            previews[evid] = .value(CachedMetadata(meta: meta))
         }
     }
     

damus/Views/NoteContentView.swift

@@ -27,9 +27,21 @@ struct NoteContentView: View {
     let event: NostrEvent
     let show_images: Bool
     let size: EventViewKind
+    let preview_height: CGFloat?
 
     @State var artifacts: NoteArtifacts
-    @State var preview: LinkViewRepresentable? = nil
+    @State var preview: LinkViewRepresentable?
+    
+    init(damus_state: DamusState, event: NostrEvent, show_images: Bool, size: EventViewKind, artifacts: NoteArtifacts) {
+        self.damus_state = damus_state
+        self.event = event
+        self.show_images = show_images
+        self.size = size
+        self._artifacts = State(initialValue: artifacts)
+        self.preview_height = lookup_cached_preview_size(previews: damus_state.previews, evid: event.id)
+        self._preview = State(initialValue: load_cached_preview(previews: damus_state.previews, evid: event.id))
+        self._artifacts = State(initialValue: render_note_content(ev: event, profiles: damus_state.profiles, privkey: damus_state.keypair.privkey))
+    }
     
     func MainContent() -> some View {
         return VStack(alignment: .leading) {
@@ -58,23 +70,21 @@ struct NoteContentView: View {
             }
             
             if let preview = self.preview, show_images {
-                preview
+                if let preview_height {
-            } else {
+                    preview
-                ForEach(artifacts.links, id:\.self) { link in
+                        .frame(height: preview_height)
-                    if let url = link {
+                } else {
-                        LinkViewRepresentable(meta: .url(url))
+                    preview
-                            .frame(height: 50)
-                    }
                 }
+            } else if let link = artifacts.links.first {
+                LinkViewRepresentable(meta: .url(link))
+                    .frame(height: 50)
             }
         }
     }
     
     var body: some View {
         MainContent()
-            .onAppear() {
-                self.artifacts = render_note_content(ev: event, profiles: damus_state.profiles, privkey: damus_state.keypair.privkey)
-            }
             .onReceive(handle_notify(.profile_updated)) { notif in
                 let profile = notif.object as! ProfileUpdate
                 let blocks = event.blocks(damus_state.keypair.privkey)
@@ -92,21 +102,19 @@ struct NoteContentView: View {
                 }
             }
             .task {
-                if let preview = damus_state.previews.lookup(self.event.id) {
+                guard self.preview == nil else {
-                    switch preview {
+                    return
-                    case .value(let view):
-                        self.preview = view
-                    case .failed:
-                        // don't try to refetch meta if we've failed
-                        return
-                    }
                 }
                 
                 if show_images, artifacts.links.count == 1 {
                     let meta = await getMetaData(for: artifacts.links.first!)
                     
-                    let view = meta.map { LinkViewRepresentable(meta: .linkmeta($0)) }
+                    damus_state.previews.store(evid: self.event.id, preview: meta)
-                    damus_state.previews.store(evid: self.event.id, preview: view)
+                    guard case .value(let cached) = damus_state.previews.lookup(self.event.id) else {
+                        return
+                    }
+                    let view = LinkViewRepresentable(meta: .linkmeta(cached))
+                    
                     self.preview = view
                 }
 
@@ -233,3 +241,23 @@ func is_image_url(_ url: URL) -> Bool {
     return str.hasSuffix("png") || str.hasSuffix("jpg") || str.hasSuffix("jpeg") || str.hasSuffix("gif")
 }
 
+func lookup_cached_preview_size(previews: PreviewCache, evid: String) -> CGFloat? {
+    guard case .value(let cached) = previews.lookup(evid) else {
+        return nil
+    }
+    
+    guard let height = cached.intrinsic_height else {
+        return nil
+    }
+    
+    return height
+}
+    
+
+func load_cached_preview(previews: PreviewCache, evid: String) -> LinkViewRepresentable? {
+    guard case .value(let meta) = previews.lookup(evid) else {
+        return nil
+    }
+    
+    return LinkViewRepresentable(meta: .linkmeta(meta))
+}