C++: Fix and test the reset function on model adapter

They were causing infinite recursion because they were calling
themselves.

Also add the missing MapModel::reset

Yet another motivation for https://github.com/slint-ui/slint/issues/3888
as the code was mixing the `reset` function on the adapter meaning
"please re-apply the adapter filter/map/sort function" with the `reset`
function on Model which means "the subclass has changed and we should
notify listeners".

Fixes #4968

api/cpp/include/slint.h

@@ -632,7 +632,7 @@ struct FilterModelInner : private_api::ModelChangeListener
     void reset() override
     {
         update_mapping();
-        target_model.reset();
+        target_model.Model<ModelData>::reset();
     }
 
     void update_mapping()
@@ -721,7 +721,7 @@ struct MapModelInner : private_api::ModelChangeListener
     {
         target_model.row_removed(index, count);
     }
-    void reset() override { target_model.reset(); }
+    void reset() override { target_model.Model<SourceModelData>::reset(); }
 
     slint::MapModel<SourceModelData, MappedModelData> &target_model;
 };
@@ -767,6 +767,10 @@ public:
     /// Returns the source model of this filter model.
     std::shared_ptr<Model<SourceModelData>> source_model() const { return model; }
 
+    /// Re-applies the model's mapping function on each row of the source model. Use this if state
+    /// external to the mapping function has changed.
+    void reset() { inner->reset(); }
+
 private:
     std::shared_ptr<private_api::MapModelInner<SourceModelData, MappedModelData>> inner;
     std::shared_ptr<slint::Model<SourceModelData>> model;
@@ -874,7 +878,7 @@ struct SortModelInner : private_api::ModelChangeListener
     void reset() override
     {
         sorted_rows_dirty = true;
-        target_model.reset();
+        target_model.Model<ModelData>::reset();
     }
 
     void ensure_sorted()
@@ -987,7 +991,7 @@ struct ReverseModelInner : private_api::ModelChangeListener
         target_model.row_removed(source_model->row_count() - first_removed_row, count);
     }
 
-    void reset() override { source_model.reset(); }
+    void reset() override { target_model.reset(); }
 
     std::shared_ptr<slint::Model<ModelData>> source_model;
     slint::ReverseModel<ModelData> &target_model;

api/cpp/tests/models.cpp

@@ -221,12 +221,47 @@ SCENARIO("Filtering Model Remove")
     REQUIRE(even_rows->row_data(1) == 4);
 }
 
+SCENARIO("Filtering Model Reset")
+{
+    auto vec_model =
+            std::make_shared<slint::VectorModel<int>>(std::vector<int> { 1, 2, 3, 4, 5, 6 });
+
+    bool even = true;
+
+    auto even_rows = std::make_shared<slint::FilterModel<int>>(
+            vec_model, [&even](auto value) { return value % 2 == !even; });
+
+    auto observer = std::make_shared<ModelObserver>();
+    even_rows->attach_peer(observer);
+
+    REQUIRE(even_rows->row_count() == 3);
+    REQUIRE(even_rows->row_data(0) == 2);
+    REQUIRE(even_rows->row_data(1) == 4);
+    REQUIRE(even_rows->row_data(2) == 6);
+
+    even = false;
+    even_rows->reset();
+
+    REQUIRE(observer->added_rows.empty());
+    REQUIRE(observer->changed_rows.empty());
+    REQUIRE(observer->removed_rows.empty());
+    REQUIRE(observer->model_reset);
+    observer->clear();
+
+    REQUIRE(even_rows->row_count() == 3);
+    REQUIRE(even_rows->row_data(0) == 1);
+    REQUIRE(even_rows->row_data(1) == 3);
+    REQUIRE(even_rows->row_data(2) == 5);
+}
+
 SCENARIO("Mapped Model")
 {
     auto vec_model = std::make_shared<slint::VectorModel<int>>(std::vector<int> { 1, 2, 3, 4 });
 
+    int to_add = 1;
+
     auto plus_one_model = std::make_shared<slint::MapModel<int, int>>(
-            vec_model, [](auto value) { return value + 1; });
+            vec_model, [&to_add](auto value) { return value + to_add; });
 
     auto observer = std::make_shared<ModelObserver>();
     plus_one_model->attach_peer(observer);
@@ -283,6 +318,21 @@ SCENARIO("Mapped Model")
     REQUIRE(plus_one_model->row_data(1) == 4);
     REQUIRE(plus_one_model->row_data(2) == 3);
     REQUIRE(plus_one_model->row_data(3) == 5);
+
+    to_add = 51;
+    plus_one_model->reset();
+
+    REQUIRE(observer->added_rows.empty());
+    REQUIRE(observer->changed_rows.empty());
+    REQUIRE(observer->removed_rows.empty());
+    REQUIRE(observer->model_reset);
+    observer->clear();
+
+    REQUIRE(plus_one_model->row_count() == 4);
+    REQUIRE(plus_one_model->row_data(0) == 151);
+    REQUIRE(plus_one_model->row_data(1) == 54);
+    REQUIRE(plus_one_model->row_data(2) == 53);
+    REQUIRE(plus_one_model->row_data(3) == 55);
 }
 
 SCENARIO("Sorted Model Insert")
@@ -400,6 +450,38 @@ SCENARIO("Sorted Model Change")
     REQUIRE(sorted_model->row_data(3) == 3);
 }
 
+SCENARIO("Sorted Model Reset")
+{
+    auto vec_model = std::make_shared<slint::VectorModel<int>>(std::vector<int> { 3, 4, 1, 2 });
+
+    bool ascending = true;
+
+    auto sorted_model =
+            std::make_shared<slint::SortModel<int>>(vec_model, [&ascending](auto lhs, auto rhs) {
+                return ascending ? lhs < rhs : rhs < lhs;
+            });
+
+    auto observer = std::make_shared<ModelObserver>();
+    sorted_model->attach_peer(observer);
+
+    REQUIRE(sorted_model->row_count() == 4);
+    REQUIRE(sorted_model->row_data(0) == 1);
+    REQUIRE(sorted_model->row_data(1) == 2);
+    REQUIRE(sorted_model->row_data(2) == 3);
+    REQUIRE(sorted_model->row_data(3) == 4);
+
+    ascending = false;
+    sorted_model->reset();
+
+    REQUIRE(sorted_model->row_count() == 4);
+    REQUIRE(sorted_model->row_data(0) == 4);
+    REQUIRE(sorted_model->row_data(1) == 3);
+    REQUIRE(sorted_model->row_data(2) == 2);
+    REQUIRE(sorted_model->row_data(3) == 1);
+
+    REQUIRE(observer->model_reset);
+}
+
 SCENARIO("Reverse Model Insert")
 {
     auto vec_model = std::make_shared<slint::VectorModel<int>>(std::vector<int> { 3, 4, 1, 2 });
@@ -493,6 +575,15 @@ SCENARIO("Reverse Model Change")
     REQUIRE(reverse_model->row_data(1) == 1);
     REQUIRE(reverse_model->row_data(2) == 10);
     REQUIRE(reverse_model->row_data(3) == 3);
+
+    vec_model->clear();
+    REQUIRE(observer->added_rows.empty());
+    REQUIRE(observer->changed_rows.empty());
+    REQUIRE(observer->removed_rows.empty());
+    REQUIRE(observer->model_reset);
+    observer->clear();
+
+    REQUIRE(reverse_model->row_count() == 0);
 }
 
 TEST_CASE("VectorModel clear and replace")