From 499aac31a4796af078b44a399e3c4dcbc5b27501 Mon Sep 17 00:00:00 2001
From: Elena Torro <elenatorro@gmail.com>
Date: Wed, 21 Jan 2026 14:49:00 +0100
Subject: [PATCH] :wrench: Improve tile invalidation to prevent visual
 flickering

When tiles are invalidated (during shape updates or page loading), the old tile
content is now kept visible until new content is rendered to replace it. This
provides a smoother visual experience during updates.
---
 render-wasm/src/render.rs          | 12 +++++-------
 render-wasm/src/render/surfaces.rs | 14 +++++++-------
 2 files changed, 12 insertions(+), 14 deletions(-)

diff --git a/render-wasm/src/render.rs b/render-wasm/src/render.rs
index 47fafce5bf..d66d8249de 100644
--- a/render-wasm/src/render.rs
+++ b/render-wasm/src/render.rs
@@ -2168,9 +2168,7 @@ impl RenderState {
     }
 
     pub fn remove_cached_tile(&mut self, tile: tiles::Tile) {
-        let rect = self.get_aligned_tile_bounds(tile);
-        self.surfaces
-            .remove_cached_tile_surface(tile, rect, self.background_color);
+        self.surfaces.remove_cached_tile_surface(tile);
     }
 
     pub fn rebuild_tiles_shallow(&mut self, tree: ShapesPoolRef) {
@@ -2191,8 +2189,8 @@ impl RenderState {
             }
         }
 
-        // Update the changed tiles
-        self.surfaces.remove_cached_tiles(self.background_color);
+        // Invalidate changed tiles - old content stays visible until new tiles render
+        self.surfaces.remove_cached_tiles();
         for tile in all_tiles {
             self.remove_cached_tile(tile);
         }
@@ -2238,8 +2236,8 @@ impl RenderState {
             }
         }
 
-        // Update the changed tiles
-        self.surfaces.remove_cached_tiles(self.background_color);
+        // Invalidate changed tiles - old content stays visible until new tiles render
+        self.surfaces.remove_cached_tiles();
         for tile in all_tiles {
             self.remove_cached_tile(tile);
         }
diff --git a/render-wasm/src/render/surfaces.rs b/render-wasm/src/render/surfaces.rs
index 00792109d8..aed1c82807 100644
--- a/render-wasm/src/render/surfaces.rs
+++ b/render-wasm/src/render/surfaces.rs
@@ -401,11 +401,10 @@ impl Surfaces {
         self.tiles.has(tile)
     }
 
-    pub fn remove_cached_tile_surface(&mut self, tile: Tile, rect: skia::Rect, color: skia::Color) {
-        // Clear the specific tile area in the cache surface with color
-        let mut paint = skia::Paint::default();
-        paint.set_color(color);
-        self.cache.canvas().draw_rect(rect, &paint);
+    pub fn remove_cached_tile_surface(&mut self, tile: Tile) {
+        // Mark tile as invalid
+        // Old content stays visible until new tile overwrites it atomically,
+        // preventing flickering during tile re-renders.
         self.tiles.remove(tile);
     }
 
@@ -422,9 +421,10 @@ impl Surfaces {
             .draw_image_rect(&image, None, rect, &skia::Paint::default());
     }
 
-    pub fn remove_cached_tiles(&mut self, color: skia::Color) {
+    pub fn remove_cached_tiles(&mut self) {
+        // New tiles will overwrite old content atomically when rendered,
+        // preventing flickering during bulk invalidation.
         self.tiles.clear();
-        self.cache.canvas().clear(color);
     }
 
     pub fn gc(&mut self) {