From cef10799e1de268459ad11898b08631703580749 Mon Sep 17 00:00:00 2001
From: Martin Valigursky <mvaligursky@snapchat.com>
Date: Wed, 27 May 2026 09:36:15 +0100
Subject: [PATCH] fix(gsplat): make writeSortIndirectArgs WGSL helper portable
 for Firefox WebGPU

The helper took the indirect dispatch buffer as a ptr<storage, ...>
parameter. Passing storage-space pointers across function boundaries
requires the 'unrestricted_pointer_parameters' WGSL language feature,
which Chrome (Dawn) enables by default but Firefox (naga) rejects with
a shader validation error.

Drop the pointer parameter and reference the global indirectDispatchArgs
binding directly. Both call sites already used that exact binding name.
---
 .../chunks/common/comp/sort-indirect-args.js  | 27 +++++++++++--------
 ...te-gsplat-projector-write-indirect-args.js |  2 +-
 .../compute-gsplat-write-indirect-args.js     |  2 +-
 3 files changed, 18 insertions(+), 13 deletions(-)

diff --git a/src/scene/shader-lib/wgsl/chunks/common/comp/sort-indirect-args.js b/src/scene/shader-lib/wgsl/chunks/common/comp/sort-indirect-args.js
index 40c00c7a716..3bf4e4e5d7a 100644
--- a/src/scene/shader-lib/wgsl/chunks/common/comp/sort-indirect-args.js
+++ b/src/scene/shader-lib/wgsl/chunks/common/comp/sort-indirect-args.js
@@ -5,8 +5,14 @@ export default /* wgsl */`
 // dispatch of ceil(count / granularity[i]) workgroups into slots
 // (baseSlot + i) for every active slot i.
 //
+// Contract: the calling shader must declare a storage binding named
+// 'indirectDispatchArgs' of type array<u32> with read_write access. The helper
+// references that global directly rather than taking it as a pointer
+// parameter, because passing storage pointers across function boundaries
+// requires the 'unrestricted_pointer_parameters' WGSL language feature, which
+// is not portable (Firefox/naga rejects it).
+//
 // Parameters:
-//   buf       - indirect dispatch buffer (plain array<u32>, not atomic).
 //   baseSlot  - index of the first slot to write (u32 offset = baseSlot * 3).
 //   count     - number of elements the sort will process.
 //   slotInfo  - sorter metadata, obtained verbatim from
@@ -16,7 +22,6 @@ export default /* wgsl */`
 //                 .y/.z/.w = per-slot elements-per-workgroup (granularity);
 //                            unused trailing entries are 0.
 fn writeSortIndirectArgs(
-    buf: ptr<storage, array<u32>, read_write>,
     baseSlot: u32,
     count: u32,
     slotInfo: vec4<u32>
@@ -27,25 +32,25 @@ fn writeSortIndirectArgs(
         let g = slotInfo.y;
         let wc = (count + g - 1u) / g;
         let off = baseSlot * 3u;
-        (*buf)[off + 0u] = wc;
-        (*buf)[off + 1u] = 1u;
-        (*buf)[off + 2u] = 1u;
+        indirectDispatchArgs[off + 0u] = wc;
+        indirectDispatchArgs[off + 1u] = 1u;
+        indirectDispatchArgs[off + 2u] = 1u;
     }
     if (n >= 2u) {
         let g = slotInfo.z;
         let wc = (count + g - 1u) / g;
         let off = (baseSlot + 1u) * 3u;
-        (*buf)[off + 0u] = wc;
-        (*buf)[off + 1u] = 1u;
-        (*buf)[off + 2u] = 1u;
+        indirectDispatchArgs[off + 0u] = wc;
+        indirectDispatchArgs[off + 1u] = 1u;
+        indirectDispatchArgs[off + 2u] = 1u;
     }
     if (n >= 3u) {
         let g = slotInfo.w;
         let wc = (count + g - 1u) / g;
         let off = (baseSlot + 2u) * 3u;
-        (*buf)[off + 0u] = wc;
-        (*buf)[off + 1u] = 1u;
-        (*buf)[off + 2u] = 1u;
+        indirectDispatchArgs[off + 0u] = wc;
+        indirectDispatchArgs[off + 1u] = 1u;
+        indirectDispatchArgs[off + 2u] = 1u;
     }
 }
 `;
diff --git a/src/scene/shader-lib/wgsl/chunks/gsplat/compute-gsplat-projector-write-indirect-args.js b/src/scene/shader-lib/wgsl/chunks/gsplat/compute-gsplat-projector-write-indirect-args.js
index 1333de4c065..6391d6b2c08 100644
--- a/src/scene/shader-lib/wgsl/chunks/gsplat/compute-gsplat-projector-write-indirect-args.js
+++ b/src/scene/shader-lib/wgsl/chunks/gsplat/compute-gsplat-projector-write-indirect-args.js
@@ -53,7 +53,7 @@ fn main() {
 
     // Sort dispatch args at sortSlotBase (no keygen slot — sort keys come from the
     // projector pass directly).
-    writeSortIndirectArgs(&indirectDispatchArgs, uniforms.sortSlotBase, count, uniforms.sortIndirectInfo);
+    writeSortIndirectArgs(uniforms.sortSlotBase, count, uniforms.sortIndirectInfo);
 }
 `;
 
diff --git a/src/scene/shader-lib/wgsl/chunks/gsplat/compute-gsplat-write-indirect-args.js b/src/scene/shader-lib/wgsl/chunks/gsplat/compute-gsplat-write-indirect-args.js
index fced9b09fd6..039aa9d925e 100644
--- a/src/scene/shader-lib/wgsl/chunks/gsplat/compute-gsplat-write-indirect-args.js
+++ b/src/scene/shader-lib/wgsl/chunks/gsplat/compute-gsplat-write-indirect-args.js
@@ -75,7 +75,7 @@ fn main(@builtin(global_invocation_id) gid: vec3u) {
     // Sort dispatch slots — delegated to the sorter-agnostic helper so this
     // shader doesn't need to know how many slots or what granularity the
     // active radix sort backend uses.
-    writeSortIndirectArgs(&indirectDispatchArgs, keygenSlot + 1u, count, uniforms.sortIndirectInfo);
+    writeSortIndirectArgs(keygenSlot + 1u, count, uniforms.sortIndirectInfo);
 
     // Write sortElementCount for sort shaders (= visibleCount)
     sortElementCountBuf[0] = count;