Component: Add information to stich together ItemTrees

Add accessors to the information necessary to stitch together the
Component-wide ItemTrees (which include DynamicNodes) into one logical
tree of Items.

api/cpp/include/slint.h

@@ -42,10 +42,12 @@ namespace slint {
 namespace private_api {
 using cbindgen_private::ComponentVTable;
 using cbindgen_private::ItemVTable;
+using ComponentRc = vtable::VRc<private_api::ComponentVTable>;
 using ComponentRef = vtable::VRef<private_api::ComponentVTable>;
+using IndexRange = cbindgen_private::IndexRange;
 using ItemRef = vtable::VRef<private_api::ItemVTable>;
 using ItemVisitorRefMut = vtable::VRefMut<cbindgen_private::ItemVisitorVTable>;
-using cbindgen_private::ComponentRc;
+using cbindgen_private::ComponentWeak;
 using cbindgen_private::ItemWeak;
 using cbindgen_private::TraversalOrder;
 }
@@ -846,6 +848,16 @@ public:
         return { &C::static_vtable, const_cast<C *>(&(**x.ptr)) };
     }
 
+    void component_at(int i, vtable::VWeak<private_api::ComponentVTable> *result) const
+    {
+        const auto &x = inner->data.at(i);
+        *result = vtable::VWeak<private_api::ComponentVTable>{x.ptr->into_dyn()};
+    }
+
+    private_api::IndexRange index_range() const {
+        return private_api::IndexRange { 0, inner->data.size() };
+    }
+
     float compute_layout_listview(const private_api::Property<float> *viewport_width,
                                   float listview_width) const
     {

api/rs/slint/lib.rs

@@ -1,6 +1,8 @@
 // Copyright © SixtyFPS GmbH <info@slint-ui.com>
 // SPDX-License-Identifier: GPL-3.0-only OR LicenseRef-Slint-commercial
 
+// cSpell: ignore buildrs
+
 /*!
 # Slint
 
@@ -283,7 +285,7 @@ pub mod re_exports {
     pub use i_slint_core::callbacks::Callback;
     pub use i_slint_core::component::{
         free_component_item_graphics_resources, init_component_items, Component, ComponentRefPin,
-        ComponentVTable,
+        ComponentVTable, ComponentWeak, IndexRange,
     };
     pub use i_slint_core::graphics::*;
     pub use i_slint_core::input::{

internal/compiler/generator/cpp.rs

@@ -848,15 +848,25 @@ fn generate_item_tree(
     let mut visit_children_statements = vec![
         "static const auto dyn_visit = [] (const uint8_t *base,  [[maybe_unused]] slint::private_api::TraversalOrder order, [[maybe_unused]] slint::private_api::ItemVisitorRefMut visitor, [[maybe_unused]] uintptr_t dyn_index) -> uint64_t {".to_owned(),
         format!("    [[maybe_unused]] auto self = reinterpret_cast<const {}*>(base);", item_tree_class_name)];
+    let mut subtree_range_statement = vec!["    std::abort();".into()];
+    let mut subtree_component_statement = vec!["    std::abort();".into()];
 
     if target_struct.members.iter().any(|(_, declaration)| {
         matches!(&declaration, Declaration::Function(func @ Function { .. }) if func.name == "visit_dynamic_children")
     }) {
         visit_children_statements
             .push("    return self->visit_dynamic_children(dyn_index, order, visitor);".into());
+        subtree_range_statement = vec![
+                format!("auto self = reinterpret_cast<const {}*>(component.instance);", item_tree_class_name),
+                "return self->subtree_range(dyn_index);".to_owned(),
+        ];
+        subtree_component_statement = vec![
+                format!("auto self = reinterpret_cast<const {}*>(component.instance);", item_tree_class_name),
+                "self->subtree_component(dyn_index, subtree_index, result);".to_owned(),
+        ];
     } else {
         visit_children_statements.push("    std::abort();".into());
-    }
+     }
 
     visit_children_statements.extend([
         "};".into(),
@@ -888,6 +898,28 @@ fn generate_item_tree(
         }),
     ));
 
+    target_struct.members.push((
+        Access::Private,
+        Declaration::Function(Function {
+            name: "get_subtree_range".into(),
+            signature: "([[maybe_unused]] slint::private_api::ComponentRef component, [[maybe_unused]] uintptr_t dyn_index) -> slint::private_api::IndexRange".into(),
+            is_static: true,
+            statements: Some(subtree_range_statement),
+            ..Default::default()
+        }),
+    ));
+
+    target_struct.members.push((
+        Access::Private,
+        Declaration::Function(Function {
+            name: "get_subtree_component".into(),
+            signature: "([[maybe_unused]] slint::private_api::ComponentRef component, [[maybe_unused]] uintptr_t dyn_index, [[maybe_unused]] uintptr_t subtree_index, [[maybe_unused]] slint::private_api::ComponentWeak *result) -> void".into(),
+            is_static: true,
+            statements: Some(subtree_component_statement),
+            ..Default::default()
+        }),
+    ));
+
     target_struct.members.push((
         Access::Private,
         Declaration::Function(Function {
@@ -910,7 +942,7 @@ fn generate_item_tree(
         format!(
             // that does not work when the parent is not a component with a ComponentVTable
             //"   *result = slint::private_api::parent_item(self->parent->self_weak.into_dyn(), self->parent->get_item_tree(), {});",
-            "self->parent->self_weak.vtable()->parent_item(self->parent->self_weak.lock()->borrow(), {}, result);",
+            "*result = {{ self->parent->self_weak, {} }};",
             parent_index,
         )
     } else {
@@ -934,6 +966,17 @@ fn generate_item_tree(
         }),
     ));
 
+    target_struct.members.push((
+        Access::Private,
+        Declaration::Function(Function {
+            name: "subtree_index".into(),
+            signature: "(slint::private_api::ComponentRef /* component */) -> uintptr_t".into(),
+            is_static: true,
+            statements: Some(vec!["/* unimplemented! */".to_owned(), "return 0;".into()]),
+            ..Default::default()
+        }),
+    ));
+
     target_struct.members.push((
         Access::Private,
         Declaration::Function(Function {
@@ -995,7 +1038,7 @@ fn generate_item_tree(
         ty: "const slint::private_api::ComponentVTable".to_owned(),
         name: format!("{}::static_vtable", item_tree_class_name),
         init: Some(format!(
-            "{{ visit_children, get_item_ref, get_item_tree, parent_item,  layout_info, slint::private_api::drop_in_place<{}>, slint::private_api::dealloc }}",
+            "{{ visit_children, get_item_ref, get_subtree_range, get_subtree_component, get_item_tree, parent_item, subtree_index, layout_info, slint::private_api::drop_in_place<{}>, slint::private_api::dealloc }}",
             item_tree_class_name)
         ),
         ..Default::default()
@@ -1181,6 +1224,8 @@ fn generate_sub_component(
     }
 
     let mut children_visitor_cases = Vec::new();
+    let mut subtrees_ranges_cases = Vec::new();
+    let mut subtrees_components_cases = Vec::new();
 
     let mut subcomponent_init_code = Vec::new();
     for sub in &component.sub_components {
@@ -1223,6 +1268,23 @@ fn generate_sub_component(
                 id = field_name,
                 base = repeater_offset,
             ));
+            subtrees_ranges_cases.push(format!(
+                "\n        {case_code} {{
+                        return self->{id}.subtree_range(dyn_index - {base});
+                    }}",
+                case_code = case_code,
+                id = field_name,
+                base = repeater_offset,
+            ));
+            subtrees_components_cases.push(format!(
+                "\n        {case_code} {{
+                        self->{id}.subtree_component(dyn_index - {base}, subtree_index, result);
+                        return;
+                    }}",
+                case_code = case_code,
+                id = field_name,
+                base = repeater_offset,
+            ));
         }
 
         target_struct.members.push((
@@ -1321,6 +1383,25 @@ fn generate_sub_component(
             i = idx,
             e_u = ensure_updated,
         ));
+        subtrees_ranges_cases.push(format!(
+            "\n        case {i}: {{
+                {e_u}
+                return self->{id}.index_range();
+            }}",
+            i = idx,
+            e_u = ensure_updated,
+            id = repeater_id,
+        ));
+        subtrees_components_cases.push(format!(
+            "\n        case {i}: {{
+                {e_u}
+                self->{id}.component_at(subtree_index, result);
+                return;
+            }}",
+            i = idx,
+            e_u = ensure_updated,
+            id = repeater_id,
+        ));
 
         target_struct.members.push((
             Access::Private,
@@ -1382,6 +1463,32 @@ fn generate_sub_component(
                 ..Default::default()
             }),
         ));
+        target_struct.members.push((
+            field_access,
+            Declaration::Function(Function {
+                name: "subtree_range".into(),
+                signature: "(uintptr_t dyn_index) const -> slint::private_api::IndexRange".into(),
+                statements: Some(vec![
+                    "[[maybe_unused]] auto self = this;".to_owned(),
+                    format!("    switch(dyn_index) {{ {} }};", subtrees_ranges_cases.join("")),
+                    "    std::abort();".to_owned(),
+                ]),
+                ..Default::default()
+            }),
+        ));
+        target_struct.members.push((
+            field_access,
+            Declaration::Function(Function {
+                name: "subtree_component".into(),
+                signature: "(uintptr_t dyn_index, [[maybe_unused]] uintptr_t subtree_index, [[maybe_unused]] slint::private_api::ComponentWeak *result) const -> void".into(),
+                statements: Some(vec![
+                    "[[maybe_unused]] auto self = this;".to_owned(),
+                    format!("    switch(dyn_index) {{ {} }};", subtrees_components_cases.join("")),
+                    "    std::abort();".to_owned(),
+                ]),
+                ..Default::default()
+            }),
+        ));
     }
 }
 

internal/compiler/generator/rust.rs

@@ -1,6 +1,8 @@
 // Copyright © SixtyFPS GmbH <info@slint-ui.com>
 // SPDX-License-Identifier: GPL-3.0-only OR LicenseRef-Slint-commercial
 
+// cSpell: ignore conv powf punct
+
 /*! module for the Rust code generator
 
 Some convention used in the generated code:
@@ -117,7 +119,7 @@ pub fn generate(doc: &Document) -> TokenStream {
     let sub_compos = llr
         .sub_components
         .iter()
-        .map(|sub_compo| generate_sub_component(sub_compo, &llr, None, quote!()))
+        .map(|sub_compo| generate_sub_component(sub_compo, &llr, None, quote!(), None))
         .collect::<Vec<_>>();
 
     let compo = generate_public_component(&llr);
@@ -243,7 +245,7 @@ fn generate_public_component(llr: &llr::PublicComponent) -> TokenStream {
     let global_container_id = format_ident!("Globals_{}", public_component_id);
 
     let component =
-        generate_item_tree(&llr.item_tree, llr, None, quote!(globals: #global_container_id));
+        generate_item_tree(&llr.item_tree, llr, None, quote!(globals: #global_container_id), None);
 
     let ctx = EvaluationContext {
         public_component: llr,
@@ -515,6 +517,7 @@ fn generate_sub_component(
     root: &llr::PublicComponent,
     parent_ctx: Option<ParentCtx>,
     extra_fields: TokenStream,
+    index_property: Option<llr::PropertyIndex>,
 ) -> TokenStream {
     let inner_component_id = inner_component_id(component);
 
@@ -527,7 +530,9 @@ fn generate_sub_component(
     let mut extra_components = component
         .popup_windows
         .iter()
-        .map(|c| generate_item_tree(c, root, Some(ParentCtx::new(&ctx, None)), quote!()))
+        .map(|c| {
+            generate_item_tree(c, root, Some(ParentCtx::new(&ctx, None)), quote!(), index_property)
+        })
         .collect::<Vec<_>>();
 
     let mut declared_property_vars = vec![];
@@ -592,6 +597,8 @@ fn generate_sub_component(
     let mut repeated_element_names: Vec<Ident> = vec![];
     let mut repeated_visit_branch: Vec<TokenStream> = vec![];
     let mut repeated_element_components: Vec<Ident> = vec![];
+    let mut repeated_subtree_ranges: Vec<TokenStream> = vec![];
+    let mut repeated_subtree_components: Vec<TokenStream> = vec![];
 
     for (idx, repeated) in component.repeated.iter().enumerate() {
         extra_components.push(generate_repeated_component(
@@ -643,6 +650,19 @@ fn generate_sub_component(
                 _self.#repeater_id.visit(order, visitor)
             }
         ));
+        repeated_subtree_ranges.push(quote!(
+            #idx => {
+                #ensure_updated
+                let (start, end) = _self.#repeater_id.range();
+                slint::re_exports::IndexRange { start, end }
+            }
+        ));
+        repeated_subtree_components.push(quote!(
+            #idx => {
+                #ensure_updated
+                *result = vtable::VRc::downgrade(&vtable::VRc::into_dyn(_self.#repeater_id.component_at(subtree_index).unwrap()))
+            }
+        ));
         repeated_element_names.push(repeater_id);
         repeated_element_components.push(rep_inner_component_id);
     }
@@ -687,6 +707,16 @@ fn generate_sub_component(
                     #sub_compo_field.apply_pin(_self).visit_dynamic_children(dyn_index - #repeater_offset, order, visitor)
                 }
             ));
+            repeated_subtree_ranges.push(quote!(
+                #repeater_offset..=#last_repeater => {
+                    #sub_compo_field.apply_pin(_self).subtree_range(dyn_index - #repeater_offset)
+                }
+            ));
+            repeated_subtree_components.push(quote!(
+                #repeater_offset..=#last_repeater => {
+                    #sub_compo_field.apply_pin(_self).subtree_component(dyn_index - #repeater_offset, subtree_index, result)
+                }
+            ));
         }
 
         sub_component_names.push(field_name);
@@ -736,6 +766,18 @@ fn generate_sub_component(
     let visibility =
         core::ptr::eq(&root.item_tree.root as *const _, component as *const _).then(|| quote!(pub));
 
+    let access_prop = |&property_index| {
+        access_member(
+            &llr::PropertyReference::Local { sub_component_path: vec![], property_index },
+            &ctx,
+        )
+    };
+    let prop = index_property.iter().map(access_prop);
+    let mut subtree_index_function = quote!(#(#prop.get() as usize)*);
+    if subtree_index_function.is_empty() {
+        subtree_index_function = quote!(core::usize::MAX);
+    }
+
     quote!(
         #[derive(slint::re_exports::FieldOffsets, Default)]
         #[const_field_offset(slint::re_exports::const_field_offset)]
@@ -796,6 +838,33 @@ fn generate_sub_component(
                     slint::re_exports::Orientation::Vertical => #layout_info_v,
                 }
             }
+
+            fn subtree_range(self: ::core::pin::Pin<&Self>, dyn_index: usize) -> slint::re_exports::IndexRange {
+                #![allow(unused)]
+                use slint::re_exports::*;
+                let _self = self;
+                match dyn_index {
+                    #(#repeated_subtree_ranges)*
+                    _ => panic!("invalid dyn_index {}", dyn_index),
+                }
+            }
+
+            fn subtree_component(self: ::core::pin::Pin<&Self>, dyn_index: usize, subtree_index: usize, result: &mut slint::re_exports::ComponentWeak) {
+                #![allow(unused)]
+                use slint::re_exports::*;
+                let _self = self;
+                match dyn_index {
+                    #(#repeated_subtree_components)*
+                    _ => panic!("invalid dyn_index {}", dyn_index),
+                };
+            }
+
+            fn index_property(self: ::core::pin::Pin<&Self>) -> usize {
+                #![allow(unused)]
+                use slint::re_exports::*;
+                let _self = self;
+                #subtree_index_function
+            }
         }
 
         #(#extra_components)*
@@ -923,8 +992,15 @@ fn generate_item_tree(
     root: &llr::PublicComponent,
     parent_ctx: Option<ParentCtx>,
     extra_fields: TokenStream,
+    index_property: Option<llr::PropertyIndex>,
 ) -> TokenStream {
-    let sub_comp = generate_sub_component(&sub_tree.root, root, parent_ctx.clone(), extra_fields);
+    let sub_comp = generate_sub_component(
+        &sub_tree.root,
+        root,
+        parent_ctx.clone(),
+        extra_fields,
+        index_property,
+    );
     let inner_component_id = self::inner_component_id(&sub_tree.root);
     let parent_component_type = parent_ctx.iter().map(|parent| {
         let parent_component_id = self::inner_component_id(parent.ctx.current_sub_component.unwrap());
@@ -1077,11 +1153,29 @@ fn generate_item_tree(
                 Self::item_tree().into()
             }
 
+            fn get_subtree_range(
+                self: ::core::pin::Pin<&Self>, index: usize) -> slint::re_exports::IndexRange
+            {
+                self.subtree_range(index)
+            }
+
+            fn get_subtree_component(
+                self: ::core::pin::Pin<&Self>, index: usize, subtree_index: usize, result: &mut slint::re_exports::ComponentWeak)
+            {
+                self.subtree_component(index, subtree_index, result);
+            }
+
+            fn subtree_index(
+                self: ::core::pin::Pin<&Self>) -> usize
+            {
+                self.index_property()
+            }
+
             fn parent_item(self: ::core::pin::Pin<&Self>, index: usize, result: &mut slint::re_exports::ItemWeak) {
                 if index == 0 {
                     #(
                         if let Some(parent) = self.parent.clone().upgrade().map(|sc| VRcMapped::origin(&sc)) {
-                            *result = slint::re_exports::ItemRc::new(parent, #parent_item_index).parent_item();
+                            *result = slint::re_exports::ItemRc::new(parent, #parent_item_index).downgrade();
                         }
                     )*
                     return;
@@ -1105,8 +1199,13 @@ fn generate_repeated_component(
     root: &llr::PublicComponent,
     parent_ctx: ParentCtx,
 ) -> TokenStream {
-    let component =
-        generate_item_tree(&repeated.sub_tree, root, Some(parent_ctx.clone()), quote!());
+    let component = generate_item_tree(
+        &repeated.sub_tree,
+        root,
+        Some(parent_ctx.clone()),
+        quote!(),
+        repeated.index_prop,
+    );
 
     let ctx = EvaluationContext {
         public_component: root,
@@ -1120,7 +1219,7 @@ fn generate_repeated_component(
     let inner_component_id = self::inner_component_id(&repeated.sub_tree.root);
 
     // let rep_inner_component_id = self::inner_component_id(&repeated.sub_tree.root.name);
-    //  let inner_component_id = self::inner_component_id(&parent_compo);
+    // let inner_component_id = self::inner_component_id(&parent_compo);
 
     let extra_fn = if let Some(listview) = &repeated.listview {
         let p_y = access_member(&listview.prop_y, &ctx);

internal/core/component.rs

@@ -1,6 +1,8 @@
 // Copyright © SixtyFPS GmbH <info@slint-ui.com>
 // SPDX-License-Identifier: GPL-3.0-only OR LicenseRef-Slint-commercial
 
+// cSpell: ignore dealloc
+
 #![warn(missing_docs)]
 
 //! This module contains the basic datastructures that are exposed to the C API
@@ -12,6 +14,15 @@ use crate::slice::Slice;
 use crate::window::WindowRc;
 use vtable::*;
 
+#[repr(C)]
+/// A range of indices
+pub struct IndexRange {
+    /// Start index
+    pub start: usize,
+    /// Index one past the last index
+    pub end: usize,
+}
+
 /// A Component is representing an unit that is allocated together
 #[vtable]
 #[repr(C)]
@@ -32,17 +43,35 @@ pub struct ComponentVTable {
         index: usize,
     ) -> core::pin::Pin<VRef<ItemVTable>>,
 
+    /// Return the range of indices below the dynamic `ItemTreeNode` at `index`
+    pub get_subtree_range:
+        extern "C" fn(core::pin::Pin<VRef<ComponentVTable>>, index: usize) -> IndexRange,
+
+    /// Return the `ComponentRc` at `subindex` below the dynamic `ItemTreeNode` at `index`
+    pub get_subtree_component: extern "C" fn(
+        core::pin::Pin<VRef<ComponentVTable>>,
+        index: usize,
+        subindex: usize,
+        result: &mut vtable::VWeak<ComponentVTable, Dyn>,
+    ),
+
     /// Return the item tree that is defined by this `Component`.
     /// The return value is an item weak because it can be null if there is no parent.
     /// And the return value is passed by &mut because ItemWeak has a destructor
     pub get_item_tree: extern "C" fn(core::pin::Pin<VRef<ComponentVTable>>) -> Slice<ItemTreeNode>,
 
+    // FIXME: This does return an invalid ItemWeak now that points to the parent repeater!
+    // FIXME: Get rid of the index and make this always return the "Item" that connects this component
+    //        to its parent-component?
     /// Return the parent item.
     /// The return value is an item weak because it can be null if there is no parent.
     /// And the return value is passed by &mut because ItemWeak has a destructor
     pub parent_item:
         extern "C" fn(core::pin::Pin<VRef<ComponentVTable>>, index: usize, result: &mut ItemWeak),
 
+    /// Return the index of the current subtree or usize::MAX if this is not a subtree
+    pub subtree_index: extern "C" fn(core::pin::Pin<VRef<ComponentVTable>>) -> usize,
+
     /// Returns the layout info for this component
     pub layout_info:
         extern "C" fn(core::pin::Pin<VRef<ComponentVTable>>, Orientation) -> LayoutInfo,

internal/core/items.rs

@@ -1,6 +1,8 @@
 // Copyright © SixtyFPS GmbH <info@slint-ui.com>
 // SPDX-License-Identifier: GPL-3.0-only OR LicenseRef-Slint-commercial
 
+// cSpell: ignore dealloc nesw
+
 /*!
 This module contains the builtin items, either in this file or in sub-modules.
 
@@ -177,6 +179,7 @@ impl ItemRc {
     pub fn new(component: vtable::VRc<ComponentVTable>, index: usize) -> Self {
         Self { component, index }
     }
+
     /// Return a `Pin<ItemRef<'a>>`
     pub fn borrow<'a>(&'a self) -> Pin<ItemRef<'a>> {
         let comp_ref_pin = vtable::VRc::borrow_pin(&self.component);
@@ -185,15 +188,29 @@ impl ItemRc {
         // lifetime of the component, which is 'a.  Pin::as_ref removes the lifetime, but we can just put it back.
         unsafe { core::mem::transmute::<Pin<ItemRef<'_>>, Pin<ItemRef<'a>>>(result) }
     }
+
     pub fn downgrade(&self) -> ItemWeak {
         ItemWeak { component: VRc::downgrade(&self.component), index: self.index }
     }
+
     /// Return the parent Item in the item tree.
     /// This is weak because it can be null if there is no parent
     pub fn parent_item(&self) -> ItemWeak {
         let comp_ref_pin = vtable::VRc::borrow_pin(&self.component);
+        let item_tree = crate::item_tree::ComponentItemTree::new(
+            comp_ref_pin.as_ref().get_item_tree().as_slice(),
+        );
+
+        if let Some(parent_index) = item_tree.parent(self.index) {
+            return ItemRc::new(self.component.clone(), parent_index).downgrade();
+        }
+
         let mut r = ItemWeak::default();
         comp_ref_pin.as_ref().parent_item(self.index, &mut r);
+        // parent_item returns the repeater node, go up one more level!
+        if let Some(rc) = r.upgrade() {
+            r = rc.parent_item();
+        }
         r
     }
 

internal/core/model.rs

@@ -1,12 +1,15 @@
 // Copyright © SixtyFPS GmbH <info@slint-ui.com>
 // SPDX-License-Identifier: GPL-3.0-only OR LicenseRef-Slint-commercial
 
+// cSpell: ignore vecmodel
+
 //! Model and Repeater
 
 // Safety: we use pointer to Repeater in the DependencyList, bue the Drop of the Repeater
 // will remove them from the list so it will not be accessed after it is dropped
 #![allow(unsafe_code)]
 
+use crate::component::ComponentVTable;
 use crate::item_tree::TraversalOrder;
 use crate::items::ItemRef;
 use crate::layout::Orientation;
@@ -567,7 +570,9 @@ impl<T> Model for ModelRc<T> {
 }
 
 /// Component that can be instantiated by a repeater.
-pub trait RepeatedComponent: crate::component::Component {
+pub trait RepeatedComponent:
+    crate::component::Component + vtable::HasStaticVTable<ComponentVTable> + 'static
+{
     /// The data corresponding to the model
     type Data: 'static;
 
@@ -615,6 +620,7 @@ impl<C: RepeatedComponent> Default for RepeaterInner<C> {
         RepeaterInner { components: Default::default(), offset: 0, cached_item_height: 0. }
     }
 }
+
 trait ErasedRepeater {
     fn row_changed(&self, row: usize);
     fn row_added(&self, index: usize, count: usize);
@@ -968,7 +974,24 @@ impl<C: RepeatedComponent> Repeater<C> {
         self.inner.borrow().components.len()
     }
 
-    /// Return true if the Repeater is empty
+    /// Return the range of indices used by this Repeater.
+    ///
+    /// Two values are necessary here since the Repeater can start to insert the data from its
+    /// model at an offset.
+    pub fn range(&self) -> (usize, usize) {
+        let inner = self.inner.borrow();
+        (inner.offset, inner.offset + inner.components.len())
+    }
+
+    pub fn component_at(&self, index: usize) -> Option<ComponentRc<C>> {
+        self.inner
+            .borrow()
+            .components
+            .get(index)
+            .map(|c| c.1.clone().expect("That was updated before!"))
+    }
+
+    /// Return true if the Repeater as empty
     pub fn is_empty(&self) -> bool {
         self.len() == 0
     }

internal/interpreter/dynamic_component.rs

@@ -1,6 +1,8 @@
 // Copyright © SixtyFPS GmbH <info@slint-ui.com>
 // SPDX-License-Identifier: GPL-3.0-only OR LicenseRef-Slint-commercial
 
+// cSpell: ignore dealloc refcell unerase
+
 use crate::{api::Value, dynamic_type, eval};
 
 use core::convert::TryInto;
@@ -12,7 +14,9 @@ use i_slint_compiler::object_tree::ElementRc;
 use i_slint_compiler::*;
 use i_slint_compiler::{diagnostics::BuildDiagnostics, object_tree::PropertyDeclaration};
 use i_slint_core::api::Window;
-use i_slint_core::component::{Component, ComponentRef, ComponentRefPin, ComponentVTable};
+use i_slint_core::component::{
+    Component, ComponentRef, ComponentRefPin, ComponentVTable, ComponentWeak, IndexRange,
+};
 use i_slint_core::item_tree::{
     ItemTreeNode, ItemVisitorRefMut, ItemVisitorVTable, TraversalOrder, VisitChildrenResult,
 };
@@ -174,9 +178,26 @@ impl Component for ErasedComponentBox {
         unsafe { get_item_ref(self.get_ref().borrow(), index) }
     }
 
+    fn get_subtree_range(self: Pin<&Self>, index: usize) -> IndexRange {
+        self.borrow().as_ref().get_subtree_range(index)
+    }
+
+    fn get_subtree_component(
+        self: Pin<&Self>,
+        index: usize,
+        subindex: usize,
+        result: &mut ComponentWeak,
+    ) {
+        self.borrow().as_ref().get_subtree_component(index, subindex, result);
+    }
+
     fn parent_item(self: Pin<&Self>, index: usize, result: &mut ItemWeak) {
         self.borrow().as_ref().parent_item(index, result)
     }
+
+    fn subtree_index(self: Pin<&Self>) -> usize {
+        self.borrow().as_ref().subtree_index()
+    }
 }
 
 i_slint_core::ComponentVTable_static!(static COMPONENT_BOX_VT for ErasedComponentBox);
@@ -1030,7 +1051,10 @@ pub(crate) fn generate_component<'id>(
         layout_info,
         get_item_ref,
         get_item_tree,
+        get_subtree_range,
+        get_subtree_component,
         parent_item,
+        subtree_index,
         drop_in_place,
         dealloc,
     };
@@ -1518,6 +1542,34 @@ unsafe extern "C" fn get_item_ref(component: ComponentRefPin, index: usize) -> P
     }
 }
 
+extern "C" fn get_subtree_range(component: ComponentRefPin, index: usize) -> IndexRange {
+    generativity::make_guard!(guard);
+    let instance_ref = unsafe { InstanceRef::from_pin_ref(component, guard) };
+    let rep_in_comp = unsafe { instance_ref.component_type.repeater[index].get_untagged() };
+    ensure_repeater_updated(instance_ref, rep_in_comp);
+
+    let repeater = rep_in_comp.offset.apply(&instance_ref.instance);
+    let (start, end) = repeater.range();
+    IndexRange { start, end }
+}
+
+extern "C" fn get_subtree_component(
+    component: ComponentRefPin,
+    index: usize,
+    subtree_index: usize,
+    result: &mut ComponentWeak,
+) {
+    generativity::make_guard!(guard);
+    let instance_ref = unsafe { InstanceRef::from_pin_ref(component, guard) };
+    let rep_in_comp = unsafe { instance_ref.component_type.repeater[index].get_untagged() };
+    ensure_repeater_updated(instance_ref, rep_in_comp);
+
+    let repeater = rep_in_comp.offset.apply(&instance_ref.instance);
+    *result = vtable::VRc::downgrade(&vtable::VRc::into_dyn(
+        repeater.component_at(subtree_index).unwrap(),
+    ))
+}
+
 extern "C" fn get_item_tree(component: ComponentRefPin) -> Slice<ItemTreeNode> {
     generativity::make_guard!(guard);
     let instance_ref = unsafe { InstanceRef::from_pin_ref(component, guard) };
@@ -1525,6 +1577,16 @@ extern "C" fn get_item_tree(component: ComponentRefPin) -> Slice<ItemTreeNode> {
     unsafe { core::mem::transmute::<&[ItemTreeNode], &[ItemTreeNode]>(tree) }.into()
 }
 
+extern "C" fn subtree_index(component: ComponentRefPin) -> usize {
+    generativity::make_guard!(guard);
+    let instance_ref = unsafe { InstanceRef::from_pin_ref(component, guard) };
+    if let Ok(value) = instance_ref.component_type.get_property(component, "index") {
+        value.try_into().unwrap()
+    } else {
+        core::usize::MAX
+    }
+}
+
 unsafe extern "C" fn parent_item(component: ComponentRefPin, index: usize, result: &mut ItemWeak) {
     generativity::make_guard!(guard);
     let instance_ref = InstanceRef::from_pin_ref(component, guard);
@@ -1549,7 +1611,7 @@ unsafe extern "C" fn parent_item(component: ComponentRefPin, index: usize, resul
                     .into_dyn()
                     .upgrade()
                     .unwrap();
-                *result = ItemRc::new(parent_rc, parent_index).parent_item();
+                *result = ItemRc::new(parent_rc, parent_index).downgrade();
             };
         }
         return;