implemented a11y for galleries

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

@@ -21,6 +21,24 @@ private struct TimelineItemAccessibilityModifier: ViewModifier {
                         action()
                     }
                 }
+        // A gallery is a container so that each of its attachments can be focussed on its own.
+        // Everything that isn't an attachment is announced when entering it, as the caption and
+        // the send info are hidden where they're shown to avoid being read twice.
+        case let timelineItem as GalleryRoomTimelineItem:
+            content
+                .accessibilityElement(children: .contain)
+                .accessibilityLabel { _ in
+                    Text(timelineItem.sender.displayName ?? timelineItem.sender.id)
+                    if let caption = timelineItem.content.caption, !caption.isBlank {
+                        Text(caption)
+                    }
+                    Text(timelineItem.localizedSendInfo)
+                }
+                .accessibilityActions {
+                    Button(L10n.commonMessageActions) {
+                        action()
+                    }
+                }
         case let timelineItem as EventBasedTimelineItemProtocol:
             content
                 .accessibilityRepresentation {

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

@@ -18,6 +18,8 @@ extension View {
         modifier(TimelineItemSendInfoModifier(sendInfo: .init(timelineItem: timelineItem,
                                                               adjustedDeliveryStatus: adjustedDeliveryStatus,
                                                               hasContentScanningFailure: hasContentScanningFailure),
+                                              // A gallery announces this when entering it instead.
+                                              isAccessibilityHidden: timelineItem is GalleryRoomTimelineItem,
                                               context: context))
     }
 }
@@ -25,6 +27,7 @@ extension View {
 /// Adds the send info to a view with the correct layout.
 private struct TimelineItemSendInfoModifier: ViewModifier {
     let sendInfo: TimelineItemSendInfo
+    let isAccessibilityHidden: Bool
     let context: TimelineViewModel.Context
     
     var layout: AnyLayout {
@@ -43,6 +46,7 @@ private struct TimelineItemSendInfoModifier: ViewModifier {
             content
             
             TimelineItemSendInfoLabel(sendInfo: sendInfo)
+                .accessibilityHidden(isAccessibilityHidden)
                 .contentShape(.rect)
                 // Tap gesture to avoid the message being detected as a button by VoiceOver
                 // (and the action shows a description that is already read to the user).