Keep message selection active when every message is unselected

Unselecting the last message used to end the selection, closing it
without the user asking. Selection mode is now its own state: Forward
starts it and it only ends with the close button, once the messages are
forwarded, when the timeline changes or the feature is turned off. With
nothing selected the forward button stays visible but disabled.

ElementX/Sources/Screens/Timeline/TimelineModels.swift

@@ -205,17 +205,15 @@ struct TimelineViewStateBindings {
     var textToBeTranslated: String?
 }
 
-/// The state of the multi-selection of messages, active as soon as an item is selected.
+/// The state of the multi-selection of messages.
 struct TimelineMessageSelectionState: Equatable {
     static let limit = 10
     
     var isEnabled = false
+    /// Stays on when every message is unselected, it only ends when closed or once the messages are forwarded.
+    var isActive = false
     var selectedEventIDs: Set<String> = []
     
-    var isActive: Bool {
-        !selectedEventIDs.isEmpty
-    }
-    
     var count: Int {
         selectedEventIDs.count
     }
@@ -228,6 +226,11 @@ struct TimelineMessageSelectionState: Equatable {
         guard let eventID else { return false }
         return selectedEventIDs.contains(eventID)
     }
+    
+    mutating func end() {
+        isActive = false
+        selectedEventIDs.removeAll()
+    }
 }
 
 struct TimelineItemActionMenuInfo: Equatable, Identifiable {

ElementX/Sources/Screens/Timeline/TimelineViewModel.swift

@@ -1200,7 +1200,7 @@ extension TimelineViewModel {
             .sink { [weak self] isEnabled in
                 self?.state.messageSelection.isEnabled = isEnabled
                 if !isEnabled {
-                    self?.state.messageSelection.selectedEventIDs.removeAll()
+                    self?.state.messageSelection.end()
                 }
             }
             .store(in: &cancellables)
@@ -1218,6 +1218,7 @@ extension TimelineViewModel {
             return
         }
         
+        state.messageSelection.isActive = true
         state.messageSelection.selectedEventIDs.insert(eventID)
     }
     
@@ -1239,7 +1240,7 @@ extension TimelineViewModel {
         guard state.messageSelection.isActive else { return }
         
         if isSwitchingTimelines {
-            state.messageSelection.selectedEventIDs.removeAll()
+            state.messageSelection.end()
             return
         }
         
@@ -1249,7 +1250,7 @@ extension TimelineViewModel {
     
     /// Ends the selection, either from the close button or once the selected messages have been forwarded.
     func clearMessageSelection() {
-        state.messageSelection.selectedEventIDs.removeAll()
+        state.messageSelection.end()
     }
     
     /// Forwards the selection in timeline order, which is unrelated to the order the messages were selected in.

ElementX/Sources/Screens/Timeline/View/Style/TimelineItemBubbledStylerView.swift

@@ -476,6 +476,7 @@ struct TimelineItemBubbledStylerView_Previews: PreviewProvider, TestablePreview
                                           emojiProvider: EmojiProvider(userSettings: userSettings),
                                           linkMetadataProvider: LinkMetadataProvider(),
                                           timelineControllerFactory: TimelineControllerFactoryMock(.init()))
+        viewModel.state.messageSelection.isActive = true
         viewModel.state.messageSelection.selectedEventIDs = ["selected"]
         return viewModel
     }()

ElementX/Sources/Screens/Timeline/View/Supplementary/TimelineMessageSelectionActionBar.swift

@@ -19,6 +19,7 @@ struct TimelineMessageSelectionActionBar: View {
             Label(L10n.actionForwardMessages(context.viewState.messageSelection.count), icon: \.forward)
         }
         .buttonStyle(.compound(.primary))
+        .disabled(context.viewState.messageSelection.selectedEventIDs.isEmpty)
         .padding(16)
         .background(Color.compound.bgCanvasDefault.ignoresSafeArea())
     }
@@ -27,14 +28,23 @@ struct TimelineMessageSelectionActionBar: View {
 // MARK: - Previews
 
 struct TimelineMessageSelectionActionBar_Previews: PreviewProvider, TestablePreview {
-    static let viewModel: TimelineViewModel = {
-        let viewModel = TimelineViewModel.mock() // A fresh instance so the shared mock isn't left selecting.
-        viewModel.state.messageSelection.selectedEventIDs = ["$1", "$2", "$3"]
-        return viewModel
-    }()
+    static let viewModel = makeViewModel(selectedEventIDs: ["$1", "$2", "$3"])
+    static let emptyViewModel = makeViewModel(selectedEventIDs: [])
     
     static var previews: some View {
         TimelineMessageSelectionActionBar(context: viewModel.context)
             .previewLayout(.sizeThatFits)
+            .previewDisplayName("Selected")
+        
+        TimelineMessageSelectionActionBar(context: emptyViewModel.context)
+            .previewLayout(.sizeThatFits)
+            .previewDisplayName("Nothing selected")
+    }
+    
+    static func makeViewModel(selectedEventIDs: Set<String>) -> TimelineViewModel {
+        let viewModel = TimelineViewModel.mock() // A fresh instance so the shared mock isn't left selecting.
+        viewModel.state.messageSelection.isActive = true
+        viewModel.state.messageSelection.selectedEventIDs = selectedEventIDs
+        return viewModel
     }
 }