Add id modifier #74

Sources/Adwaita/AnyView+.swift

@@ -390,4 +390,11 @@ extension AnyView {
         BreakpointBin(condition: .naturalHeight(padding: padding), matches: matches) { self }
     }
 
+    /// Build the UI from scratch once the identifier changes.
+    /// - Parameter id: The identifier.
+    public func id(_ id: CustomStringConvertible) -> AnyView {
+        ViewStack(id: id) { _ in self }
+            .limitChildren()
+    }
+
 }

Sources/Adwaita/View/ViewStack.swift

@@ -16,6 +16,8 @@ public struct ViewStack: AdwaitaWidget {
     var id: CustomStringConvertible
     /// Whether the view stack allocates the same height and width for all children.
     var homogeneous: Bool?
+    /// Whether to limit the stack to one child (always redraw the UI when the id changes).
+    var limitChildren: Bool?
 
     /// Initialize the stack.
     /// - Parameters:
@@ -87,14 +89,30 @@ public struct ViewStack: AdwaitaWidget {
             gtk_stack_set_vhomogeneous(storage.opaquePointer, homogeneous.cBool)
             gtk_stack_set_hhomogeneous(storage.opaquePointer, homogeneous.cBool)
         }
+        if let limitChildren, limitChildren {
+            for element in storage.content where element.key != id.description {
+                guard let first = element.value.first else {
+                    continue
+                }
+                gtk_stack_remove(storage.opaquePointer, first.opaquePointer?.cast())
+                storage.content.removeValue(forKey: element.key)
+            }
+        }
         storage.previousState = self
     }
 
     /// Whether the view stack allocates the same height and width for all children.
     /// - Parameter homogeneous: Whether this is enabled.
     /// - Returns: The stack.
-    public func homogeneous(_ homogeneous: Bool? = nil) -> Self {
+    public func homogeneous(_ homogeneous: Bool? = true) -> Self {
         modify { $0.homogeneous = homogeneous }
     }
 
+    /// Whether to limit the stack to one child (always redraw the UI when the id changes).
+    /// - Parameter limit: Whether to limit the stack to one child.
+    /// - Returns: The stack.
+    public func limitChildren(_ limitChildren: Bool? = true) -> Self {
+        modify { $0.limitChildren = limitChildren }
+    }
+
 }