From 3f4d699395b6e69df5447853e122777116ca0868 Mon Sep 17 00:00:00 2001
From: Alejandro Alonso <alejandroalonsofernandez@gmail.com>
Date: Tue, 28 Oct 2025 12:20:02 +0100
Subject: [PATCH] :bug: Prevent rendering of unused fill slots in shapes

---
 common/src/app/common/types/fills/impl.cljc | 12 +++++++++---
 render-wasm/src/wasm/fills.rs               |  5 ++++-
 2 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/common/src/app/common/types/fills/impl.cljc b/common/src/app/common/types/fills/impl.cljc
index 26f3757c6e..beebc29655 100644
--- a/common/src/app/common/types/fills/impl.cljc
+++ b/common/src/app/common/types/fills/impl.cljc
@@ -301,11 +301,17 @@
 
      IHeapWritable
      (-get-byte-size [_]
-       (- (.-byteLength dbuffer) 4))
+       ;; Include the 4-byte header with the fill count
+       (+ 4 (* size FILL-U8-SIZE)))
 
      (-write-to [_ heap offset]
-       (let [buffer' (.-buffer ^js/DataView dbuffer)]
-         (.set heap (js/Uint32Array. buffer' 4) offset)))
+       (let [buffer' (.-buffer ^js/DataView dbuffer)
+            ;; Calculate byte size: 4 bytes header + (size * FILL-U8-SIZE)
+             byte-size (+ 4 (* size FILL-U8-SIZE))
+             ;; Create Uint32Array with exact size needed (convert bytes to u32 elements)
+             u32-array (js/Uint32Array. buffer' 0 (/ byte-size 4))]
+         ;; Copy from offset 0 to include the header with fill count
+         (.set heap u32-array offset)))
 
      IBinaryFills
      (-get-image-ids [_]
diff --git a/render-wasm/src/wasm/fills.rs b/render-wasm/src/wasm/fills.rs
index 24935e7491..46901816e4 100644
--- a/render-wasm/src/wasm/fills.rs
+++ b/render-wasm/src/wasm/fills.rs
@@ -70,7 +70,10 @@ pub fn parse_fills_from_bytes(buffer: &[u8], num_fills: usize) -> Vec<shapes::Fi
 pub extern "C" fn set_shape_fills() {
     with_current_shape_mut!(state, |shape: &mut Shape| {
         let bytes = mem::bytes();
-        let fills = parse_fills_from_bytes(&bytes, bytes.len() / RAW_FILL_DATA_SIZE);
+        // The first byte contains the actual number of fills
+        let num_fills = bytes.first().copied().unwrap_or(0) as usize;
+        // Skip the first 4 bytes (header with fill count) and parse only the actual fills
+        let fills = parse_fills_from_bytes(&bytes[4..], num_fills);
         shape.set_fills(fills);
     });
 }