2 files changed, 58 insertions, 1 deletions
diff --git a/include/cru/ui/model/IListChangeNotify.h b/include/cru/ui/model/IListChangeNotify.h
new file mode 100644
index 00000000..a9fcd65b
--- /dev/null
+++ b/include/cru/ui/model/IListChangeNotify.h
@@ -0,0 +1,47 @@
+#pragma once
+#include "../Base.h"
+#include "cru/common/Base.h"
+#include "cru/common/Event.h"
+
+namespace cru::ui::model {
+enum ListChangeType {
+  kItemAdd,
+  kItemRemove,
+  kItemSet,
+  kItemMove,
+  kClear,
+};
+
+struct CRU_UI_API ListChange {
+  ListChangeType type;
+  union {
+    Index position;
+  };
+  union {
+    Index count;
+    Index new_position;
+  };
+
+  constexpr static ListChange ItemAdd(Index index, Index count = 1) {
+    return {ListChangeType::kItemAdd, index, count};
+  }
+
+  constexpr static ListChange ItemRemove(Index index, Index count = 1) {
+    return {ListChangeType::kItemRemove, index, count};
+  }
+
+  constexpr static ListChange ItemSet(Index index, Index count = 1) {
+    return {ListChangeType::kItemSet, index, count};
+  }
+
+  constexpr static ListChange ItemMove(Index position, Index new_position) {
+    return {ListChangeType::kItemMove, position, new_position};
+  }
+
+  constexpr static ListChange Clear() { return {ListChangeType::kClear}; }
+};
+
+struct CRU_UI_API IListChangeNotify : virtual Interface {
+  virtual IEvent<ListChange>* ListChangeEvent() = 0;
+};
+}  // namespace cru::ui::model
diff --git a/include/cru/ui/style/StyleRuleSet.h b/include/cru/ui/style/StyleRuleSet.h
index 8bf9c9ff..8f3495bc 100644
--- a/include/cru/ui/style/StyleRuleSet.h
+++ b/include/cru/ui/style/StyleRuleSet.h
@@ -2,6 +2,7 @@
 #include "StyleRule.h"
 #include "cru/common/Base.h"
 #include "cru/common/Event.h"
+#include "cru/ui/model/IListChangeNotify.h"
 
 #include <cstddef>
 
@@ -12,7 +13,7 @@ namespace cru::ui::style {
  * mutable and has reference semantics. Change of it will be notified by
  * StyleRuleSet::ChangeEvent.
  */
-class CRU_UI_API StyleRuleSet : public Object {
+class CRU_UI_API StyleRuleSet : public Object, public model::IListChangeNotify {
  public:
   StyleRuleSet() = default;
   explicit StyleRuleSet(std::shared_ptr<StyleRuleSet> parent);
@@ -50,11 +51,20 @@ class CRU_UI_API StyleRuleSet : public Object {
   // change ...). Subscribe to this and update style change listeners and style.
   IEvent<std::nullptr_t>* ChangeEvent() { return &change_event_; }
 
+  IEvent<model::ListChange>* ListChangeEvent() override {
+    return &list_change_event_;
+  }
+
  private:
   void RaiseChangeEvent() { change_event_.Raise(nullptr); }
+  void RaiseChangeEvent(model::ListChange list_change) {
+    list_change_event_.Raise(list_change);
+    change_event_.Raise(nullptr);
+  }
 
  private:
   Event<std::nullptr_t> change_event_;
+  Event<model::ListChange> list_change_event_;
 
   std::shared_ptr<StyleRuleSet> parent_ = nullptr;
   EventRevokerGuard parent_change_event_guard_;