From a943fbed3e64abd5061c8616a71790e6dabe3807 Mon Sep 17 00:00:00 2001
From: Michal Ziulek <michalziulek@gmail.com>
Date: Sun, 10 Apr 2022 19:30:34 +0200
Subject: [PATCH]  gpu: make RenderPipeline.fragment optional (#212)

pipeline with vertex stage only is perfectly valid

Helps hexops/mach#182
---
 gpu/src/NativeInstance.zig | 22 ++++++++++++----------
 gpu/src/RenderPipeline.zig |  2 +-
 2 files changed, 13 insertions(+), 11 deletions(-)

diff --git a/gpu/src/NativeInstance.zig b/gpu/src/NativeInstance.zig
index 09fcbaa6..b314695e 100644
--- a/gpu/src/NativeInstance.zig
+++ b/gpu/src/NativeInstance.zig
@@ -807,15 +807,17 @@ inline fn convertRenderPipelineDescriptor(
         };
     }
 
-    tmp_fragment_state.* = c.WGPUFragmentState{
-        .nextInChain = null,
-        .module = @ptrCast(c.WGPUShaderModule, d.fragment.module.ptr),
-        .entryPoint = d.vertex.entry_point,
-        .constantCount = if (d.fragment.constants) |v| @intCast(u32, v.len) else 0,
-        .constants = if (d.fragment.constants) |v| @ptrCast([*]const c.WGPUConstantEntry, v.ptr) else null,
-        .targetCount = if (d.fragment.targets) |v| @intCast(u32, v.len) else 0,
-        .targets = if (d.fragment.targets) |v| @ptrCast([*]const c.WGPUColorTargetState, v.ptr) else null,
-    };
+    if (d.fragment) |frag| {
+        tmp_fragment_state.* = c.WGPUFragmentState{
+            .nextInChain = null,
+            .module = @ptrCast(c.WGPUShaderModule, frag.module.ptr),
+            .entryPoint = frag.entry_point,
+            .constantCount = if (frag.constants) |v| @intCast(u32, v.len) else 0,
+            .constants = if (frag.constants) |v| @ptrCast([*]const c.WGPUConstantEntry, v.ptr) else null,
+            .targetCount = if (frag.targets) |v| @intCast(u32, v.len) else 0,
+            .targets = if (frag.targets) |v| @ptrCast([*]const c.WGPUColorTargetState, v.ptr) else null,
+        };
+    }
 
     return c.WGPURenderPipelineDescriptor{
         .nextInChain = null,
@@ -844,7 +846,7 @@ inline fn convertRenderPipelineDescriptor(
             .mask = d.multisample.mask,
             .alphaToCoverageEnabled = d.multisample.alpha_to_coverage_enabled,
         },
-        .fragment = tmp_fragment_state,
+        .fragment = if (d.fragment != null) tmp_fragment_state else null,
     };
 }
 
diff --git a/gpu/src/RenderPipeline.zig b/gpu/src/RenderPipeline.zig
index 08a77f37..37c35803 100644
--- a/gpu/src/RenderPipeline.zig
+++ b/gpu/src/RenderPipeline.zig
@@ -43,7 +43,7 @@ pub const Descriptor = struct {
     primitive: PrimitiveState,
     depth_stencil: ?*const DepthStencilState,
     multisample: MultisampleState,
-    fragment: *const FragmentState,
+    fragment: ?*const FragmentState,
 };
 
 pub const CreateStatus = enum(u32) {