From c2c229445bc1f62c430fe14dfa47925bca39dbc8 Mon Sep 17 00:00:00 2001
From: Simon Hausmann <simon.hausmann@slint.dev>
Date: Thu, 3 Aug 2023 14:24:08 +0200
Subject: [PATCH] Fix panic when code in init callback of conditional/repeater
 re-triggers repeater traversal

Don't call init() while mutably borrowing the repeater's inner.

Fixes #3214
---
 internal/core/model.rs                  | 17 +++++++-----
 tests/cases/models/init_recursion.slint | 36 +++++++++++++++++++++++++
 2 files changed, 46 insertions(+), 7 deletions(-)
 create mode 100644 tests/cases/models/init_recursion.slint

diff --git a/internal/core/model.rs b/internal/core/model.rs
index 1a3508f30e4..37c07c87cf0 100644
--- a/internal/core/model.rs
+++ b/internal/core/model.rs
@@ -896,27 +896,30 @@ impl<C: RepeatedItemTree + 'static> Repeater<C> {
         model: &ModelRc<C::Data>,
         count: usize,
     ) -> bool {
+        let mut indices_to_init = Vec::new();
         let mut inner = self.0.inner.borrow_mut();
         inner.instances.resize_with(count, || (RepeatedInstanceState::Dirty, None));
         let offset = inner.offset;
         let mut any_items_created = false;
         for (i, c) in inner.instances.iter_mut().enumerate() {
             if c.0 == RepeatedInstanceState::Dirty {
-                let created = if c.1.is_none() {
+                if c.1.is_none() {
                     any_items_created = true;
                     c.1 = Some(init());
-                    true
-                } else {
-                    false
+                    indices_to_init.push(i);
                 };
                 c.1.as_ref().unwrap().update(i + offset, model.row_data(i + offset).unwrap());
-                if created {
-                    c.1.as_ref().unwrap().init();
-                }
                 c.0 = RepeatedInstanceState::Clean;
             }
         }
         self.data().is_dirty.set(false);
+
+        drop(inner);
+        let inner = self.0.inner.borrow();
+        for item in indices_to_init.into_iter().filter_map(|index| inner.instances.get(index)) {
+            item.1.as_ref().unwrap().init();
+        }
+
         any_items_created
     }
 
diff --git a/tests/cases/models/init_recursion.slint b/tests/cases/models/init_recursion.slint
new file mode 100644
index 00000000000..7e387e1ad61
--- /dev/null
+++ b/tests/cases/models/init_recursion.slint
@@ -0,0 +1,36 @@
+// Copyright © SixtyFPS GmbH <info@slint.dev>
+// SPDX-License-Identifier: GPL-3.0-only OR LicenseRef-Slint-Royalty-free-1.1 OR LicenseRef-Slint-commercial
+
+TestCase := Rectangle {
+    property <length> test-height: layout.preferred-height;
+    property <bool> test: self.test-height != 0;
+
+    layout := VerticalLayout {
+        if true: TextInput {
+            // Trigger a call into the layout
+            init => { debug(self.y); }
+        }
+    }
+}
+
+/*
+```cpp
+auto handle = TestCase::create();
+const TestCase &instance = *handle;
+
+assert(instance.get_test_height() != 0.);
+```
+
+
+```rust
+let instance = TestCase::new().unwrap();
+
+assert!(instance.get_test_height() != 0.);
+```
+
+```js
+var instance = new slint.TestCase();
+
+assert(instance.test_height != 0.);
+```
+*/