From 1d454f379099e27130640b57a24ec375af85131b Mon Sep 17 00:00:00 2001
From: Alejandro Alonso <alejandroalonsofernandez@gmail.com>
Date: Mon, 20 Apr 2026 08:50:40 +0200
Subject: [PATCH] :bug: Fix stale tile cache when flex reflow changes modifier
 set between frames

---
 render-wasm/src/main.rs              |  7 ++++++-
 render-wasm/src/render.rs            |  2 --
 render-wasm/src/state/shapes_pool.rs | 26 +++++++++++++++++++++++++-
 3 files changed, 31 insertions(+), 4 deletions(-)

diff --git a/render-wasm/src/main.rs b/render-wasm/src/main.rs
index 740fae8104..ee3a7815f3 100644
--- a/render-wasm/src/main.rs
+++ b/render-wasm/src/main.rs
@@ -866,7 +866,12 @@ pub extern "C" fn set_structure_modifiers() -> Result<()> {
 #[wasm_error]
 pub extern "C" fn clean_modifiers() -> Result<()> {
     with_state_mut!(state, {
-        state.shapes.clean_all();
+        let prev_modifier_ids = state.shapes.clean_all();
+        if !prev_modifier_ids.is_empty() {
+            state
+                .render_state
+                .update_tiles_shapes(&prev_modifier_ids, &mut state.shapes)?;
+        }
     });
     Ok(())
 }
diff --git a/render-wasm/src/render.rs b/render-wasm/src/render.rs
index 93fd9ce591..5df0326ace 100644
--- a/render-wasm/src/render.rs
+++ b/render-wasm/src/render.rs
@@ -1775,8 +1775,6 @@ impl RenderState {
             self.render_shape_tree_partial(base_object, tree, timestamp, false)?;
         }
         self.flush_and_submit();
-        wapi::notify_tiles_render_complete!();
-
         Ok(())
     }
 
diff --git a/render-wasm/src/state/shapes_pool.rs b/render-wasm/src/state/shapes_pool.rs
index 436d57f2ea..7e03befa01 100644
--- a/render-wasm/src/state/shapes_pool.rs
+++ b/render-wasm/src/state/shapes_pool.rs
@@ -278,11 +278,35 @@ impl ShapesPoolImpl {
         }
     }
 
-    pub fn clean_all(&mut self) {
+    /// Clears transient per-frame state (modifiers, structure, scale_content)
+    /// and returns the list of UUIDs that had a `modifier` applied at the
+    /// moment of cleaning. The caller can use that list to re-sync the tile
+    /// index / tile cache for those shapes: after cleaning their modifier is
+    /// gone, but if we don't touch their tiles they keep pointing at the
+    /// previous modified position and the tile texture cache may serve stale
+    /// pixels.
+    pub fn clean_all(&mut self) -> Vec<Uuid> {
         self.clean_shape_cache();
+
+        let modified_uuids: Vec<Uuid> = if self.modifiers.is_empty() {
+            Vec::new()
+        } else {
+            let mut idx_to_uuid: HashMap<usize, Uuid> =
+                HashMap::with_capacity(self.uuid_to_idx.len());
+            for (uuid, idx) in self.uuid_to_idx.iter() {
+                idx_to_uuid.insert(*idx, *uuid);
+            }
+            self.modifiers
+                .keys()
+                .filter_map(|idx| idx_to_uuid.get(idx).copied())
+                .collect()
+        };
+
         self.modifiers = HashMap::default();
         self.structure = HashMap::default();
         self.scale_content = HashMap::default();
+
+        modified_uuids
     }
 
     pub fn subtree(&self, id: &Uuid) -> ShapesPoolImpl {