From 8826cfb7a0380ce0dd8b9e264be60cf9560d1a0e Mon Sep 17 00:00:00 2001
From: Stephen Gutekanst <stephen@hexops.com>
Date: Tue, 16 Aug 2022 20:36:12 -0700
Subject: [PATCH] gpu: add type-safety for chaining
 ExternalTexture.BindingLayout

Signed-off-by: Stephen Gutekanst <stephen@hexops.com>
---
 gpu/src/bind_group_layout.zig | 8 +++++++-
 gpu/src/external_texture.zig  | 1 -
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/gpu/src/bind_group_layout.zig b/gpu/src/bind_group_layout.zig
index 5ad696de..1c8cbd71 100644
--- a/gpu/src/bind_group_layout.zig
+++ b/gpu/src/bind_group_layout.zig
@@ -6,11 +6,17 @@ const Texture = @import("texture.zig").Texture;
 const TextureView = @import("texture_view.zig").TextureView;
 const StorageTextureBindingLayout = @import("types.zig").StorageTextureBindingLayout;
 const StorageTextureAccess = @import("types.zig").StorageTextureAccess;
+const ExternalTexture = @import("external_texture.zig").ExternalTexture;
 const Impl = @import("interface.zig").Impl;
 
 pub const BindGroupLayout = opaque {
     pub const Entry = extern struct {
-        next_in_chain: ?*const ChainedStruct = null,
+        pub const NextInChain = extern union {
+            generic: ?*const ChainedStruct,
+            external_texture_binding_layout: *const ExternalTexture.BindingLayout,
+        };
+
+        next_in_chain: NextInChain = .{ .generic = null },
         binding: u32,
         visibility: ShaderStageFlags,
         buffer: Buffer.BindingLayout = .{},
diff --git a/gpu/src/external_texture.zig b/gpu/src/external_texture.zig
index fddb5d17..43a1d220 100644
--- a/gpu/src/external_texture.zig
+++ b/gpu/src/external_texture.zig
@@ -8,7 +8,6 @@ pub const ExternalTexture = opaque {
         external_texture: *ExternalTexture,
     };
 
-    /// TODO: Can be chained in gpu.BindGroupLayout.Entry
     pub const BindingLayout = extern struct {
         chain: ChainedStruct = .{ .next = null, .s_type = .external_texture_binding_layout },
     };