From cd239d24f88f2e58f70ebc89bec298458f63b431 Mon Sep 17 00:00:00 2001
From: Alejandro Alonso <alejandro.alonso@kaleidos.net>
Date: Tue, 16 Jun 2026 09:52:19 +0200
Subject: [PATCH] :bug: Fix transparent tile holes in viewer WASM render
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Use direct backbuffer tile compositing for render_sync_shape (viewer/thumbnails)
instead of the tile texture atlas cache, which left 512×512 transparent holes.
---
 render-wasm/src/render.rs | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/render-wasm/src/render.rs b/render-wasm/src/render.rs
index 152de04143..f95685a4c5 100644
--- a/render-wasm/src/render.rs
+++ b/render-wasm/src/render.rs
@@ -970,7 +970,8 @@ impl RenderState {
 
         // Viewer masked passes render a partial scene. Reusing the tile texture cache would
         // SrcOver-blend onto textures from the previous pass and leak pixels into the blob.
-        if self.viewer_masked_pass() {
+        // `render_sync_shape` (viewer/thumbnails) uses the same direct backbuffer path.
+        if self.viewer_masked_pass() || self.viewer_render_root.is_some() {
             // Use viewbox-aligned bounds (not grid-snapped) to match interactive-transform
             // compositing and avoid a visible offset vs the DOM canvas.
             let tile_rect = self.get_current_tile_bounds()?;