fix(headless): add nullptr checks for GPU resource creation

- NodeRegistry::create_texture: skip texture creation when device is nullptr
- Post-process helpers: skip pipeline/bind group creation in headless mode
- SamplerCache: return nullptr for headless mode
- BindGroupLayoutBuilder/BindGroupBuilder: skip creation with null device
- RenderPipelineBuilder: skip shader module and pipeline creation in headless
- PlaceholderEffect: skip sampler creation in headless mode
- RotatingCubeEffect: early return in constructor for headless mode

WIP: Some effects (GaussianBlur, etc.) still need headless checks

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

1 files changed, 15 insertions, 0 deletions

diff --git a/src/gpu/post_process_helper.cc b/src/gpu/post_process_helper.cc
index 5f2ff56..6026f6e 100644
--- a/src/gpu/post_process_helper.cc
+++ b/src/gpu/post_process_helper.cc
@@ -14,6 +14,11 @@
 WGPURenderPipeline create_post_process_pipeline(WGPUDevice device,
                                                 WGPUTextureFormat format,
                                                 const char* shader_code) {
+  // Headless mode: skip pipeline creation
+  if (device == nullptr) {
+    return nullptr;
+  }
+
   WGPUBindGroupLayout bgl =
       BindGroupLayoutBuilder()
           .sampler(PP_BINDING_SAMPLER, WGPUShaderStage_Fragment)
@@ -40,6 +45,11 @@ WGPURenderPipeline create_post_process_pipeline(WGPUDevice device,
 WGPURenderPipeline create_post_process_pipeline_simple(WGPUDevice device,
                                                        WGPUTextureFormat format,
                                                        const char* shader_code) {
+  // Headless mode: skip pipeline creation
+  if (device == nullptr) {
+    return nullptr;
+  }
+
   WGPUBindGroupLayout bgl =
       BindGroupLayoutBuilder()
           .sampler(PP_BINDING_SAMPLER, WGPUShaderStage_Fragment)
@@ -67,6 +77,11 @@ static GpuBuffer g_dummy_buffer = {nullptr, 0};
 void pp_update_bind_group(WGPUDevice device, WGPURenderPipeline pipeline,
                           WGPUBindGroup* bind_group, WGPUTextureView input_view,
                           GpuBuffer uniforms, GpuBuffer effect_params) {
+  // Headless mode: skip bind group creation
+  if (device == nullptr || pipeline == nullptr) {
+    return;
+  }
+
   if (!g_dummy_buffer.buffer) {
     g_dummy_buffer = gpu_create_buffer(device, 32, WGPUBufferUsage_Uniform);
   }