Add a "load more" button instead of always inserting events in timelines

Changelog-Added: Add a "load more" button instead of always inserting events in timelines

damus/Views/TimelineView.swift

@@ -12,50 +12,12 @@ enum TimelineAction {
     case navigating
 }
 
-struct InnerTimelineView: View {
-    @Binding var events: [NostrEvent]
-    let damus: DamusState
-    let show_friend_icon: Bool
-    let filter: (NostrEvent) -> Bool
-    @State var nav_target: NostrEvent? = nil
-    @State var navigating: Bool = false
-    
-    var MaybeBuildThreadView: some View {
-        Group {
-            if let ev = nav_target {
-                BuildThreadV2View(damus: damus, event_id: (ev.inner_event ?? ev).id)
-            } else {
-                EmptyView()
-            }
-        }
-    }
-    
-    var body: some View {
-        NavigationLink(destination: MaybeBuildThreadView, isActive: $navigating) {
-            EmptyView()
-        }
-        LazyVStack(spacing: 0) {
-            if events.isEmpty {
-                EmptyTimelineView()
-            } else {
-                ForEach(events.filter(filter), id: \.id) { (ev: NostrEvent) in
-                    EventView(damus: damus, event: ev, has_action_bar: true)
-                        .onTapGesture {
-                            nav_target = ev
-                            navigating = true
-                        }
-                        .padding(.top, 10)
-                }
-            }
-        }
-        .padding(.horizontal)
-    }
-}
-
 struct TimelineView: View {
-    
-    @Binding var events: [NostrEvent]
+    @ObservedObject var events: EventHolder
     @Binding var loading: Bool
+    @State var offset = CGFloat.zero
+    
+    @Environment(\.colorScheme) var colorScheme
 
     let damus: DamusState
     let show_friend_icon: Bool
@@ -65,37 +27,66 @@ struct TimelineView: View {
         MainContent
     }
     
+    func handle_scroll(_ proxy: GeometryProxy) {
+        let offset = -proxy.frame(in: .named("scroll")).origin.y
+        guard offset != -0.0 else {
+            return
+        }
+        self.events.should_queue = offset > 0
+    }
+    
+    var realtime_bar_opacity: Double {
+        colorScheme == .dark ? 0.2 : 0.1
+    }
+    
     var MainContent: some View {
         ScrollViewReader { scroller in
-            ScrollView {
-                InnerTimelineView(events: loading ? .constant(Constants.EXAMPLE_EVENTS) : $events, damus: damus, show_friend_icon: show_friend_icon, filter: loading ? { _ in true } : filter)
-                    .redacted(reason: loading ? .placeholder : [])
-                    .shimmer(loading)
-                    .disabled(loading)
-            }
-            .onReceive(NotificationCenter.default.publisher(for: .scroll_to_top)) { _ in
-                guard let event = events.filter(self.filter).first else {
-                    return
+            ZStack {
+                VStack {
+                    LoadMoreButton(events: events, scroller: scroller)
+                        .padding([.top], 10)
+                    Spacer()
+                }
+                .zIndex(10.0)
+        
+                ScrollView {
+                    InnerTimelineView(events: events, damus: damus, show_friend_icon: show_friend_icon, filter: loading ? { _ in true } : filter)
+                        .redacted(reason: loading ? .placeholder : [])
+                        .shimmer(loading)
+                        .disabled(loading)
+                        .background(GeometryReader { proxy -> Color in
+                            DispatchQueue.main.async {
+                                handle_scroll(proxy)
+                            }
+                            return Color.clear
+                        })
+                }
+                .overlay(
+                    Rectangle()
+                        .fill(RECTANGLE_GRADIENT.opacity(realtime_bar_opacity))
+                        .offset(y: -1)
+                        .frame(height: events.should_queue ? 0 : 8)
+                        ,
+                    alignment: .top
+                )
+                .buttonStyle(BorderlessButtonStyle())
+                .coordinateSpace(name: "scroll")
+                .onReceive(NotificationCenter.default.publisher(for: .scroll_to_top)) { _ in
+                    guard let event = events.events.filter(self.filter).first else {
+                        return
+                    }
+                    scroll_to_event(scroller: scroller, id: event.id, delay: 0.0, animate: true, anchor: .top)
                 }
-                scroll_to_event(scroller: scroller, id: event.id, delay: 0.0, animate: true, anchor: .top)
             }
         }
     }
 }
 
 struct TimelineView_Previews: PreviewProvider {
+    @StateObject static var events = test_event_holder
     static var previews: some View {
-        TimelineView(events: .constant(Constants.EXAMPLE_EVENTS), loading: .constant(true), damus: Constants.EXAMPLE_DEMOS, show_friend_icon: true, filter: { _ in true })
+        TimelineView(events: events, loading: .constant(true), damus: Constants.EXAMPLE_DEMOS, show_friend_icon: true, filter: { _ in true })
     }
 }
 
 
-struct NavigationLazyView<Content: View>: View {
-    let build: () -> Content
-    init(_ build: @autoclosure @escaping () -> Content) {
-        self.build = build
-    }
-    var body: Content {
-        build()
-    }
-}