Add additional options for navigation split view

- Whether it is collapsed
- Whether the content is visible if it is collapsed

Sources/Adwaita/View/NavigationSplitView.swift

@@ -14,6 +14,10 @@ public struct NavigationSplitView: Widget {
     var sidebar: () -> Body
     /// The split view's main content.
     var content: () -> Body
+    /// Whether the split view is collapsed.
+    var collapsed = false
+    /// Whether the content is visible (if the split view is collapsed).
+    var showContent: Binding<Bool>?
 
     /// The sidebar content's id.
     let sidebarID = "sidebar"
@@ -48,7 +52,14 @@ public struct NavigationSplitView: Widget {
         adw_navigation_split_view_set_content(.init(splitView), mainPage?.cast())
         content[contentID] = [mainContent]
 
-        return .init(.init(splitView), content: content)
+        let storage = ViewStorage(.init(splitView), content: content)
+        update(storage, modifiers: modifiers, updateProperties: true)
+
+        storage.notify(name: "show-content") {
+            showContent?.wrappedValue = adw_navigation_split_view_get_show_content(storage.pointer) != 0
+        }
+
+        return storage
     }
 
     /// Update the view storage of the navigation split view widget.
@@ -67,6 +78,35 @@ public struct NavigationSplitView: Widget {
                 .widget(modifiers: modifiers)
                 .update(storage, modifiers: modifiers, updateProperties: updateProperties)
         }
+        guard updateProperties else {
+            return
+        }
+        let collapsed = adw_navigation_split_view_get_collapsed(storage.pointer) != 0
+        if collapsed != self.collapsed {
+            adw_navigation_split_view_set_collapsed(storage.pointer, self.collapsed.cBool)
+        }
+        let showContent = adw_navigation_split_view_get_show_content(storage.pointer) != 0
+        if let binding = self.showContent, showContent != binding.wrappedValue {
+            adw_navigation_split_view_set_show_content(storage.pointer, binding.wrappedValue.cBool)
+        }
+    }
+
+    /// Whether the navigation split view is collapsed, meaning in its compact form.
+    /// - Parameter collapsed: Whether the view is collapsed.
+    /// - Returns: The navigation split view.
+    public func collapsed(_ collapsed: Bool) -> Self {
+        var newSelf = self
+        newSelf.collapsed = collapsed
+        return newSelf
+    }
+
+    /// Whether the content view is visible if the split view is collapsed.
+    /// - Parameter showContent: Whether the content view is visible.
+    /// - Returns: The navigation split view.
+    public func showContent(_ showContent: Binding<Bool>) -> Self {
+        var newSelf = self
+        newSelf.showContent = showContent
+        return newSelf
     }
 
 }