Add render pass and pipeline sample count validation.

Author: chinmaygarde

impeller/renderer/backend/metal/pipeline_library_mtl.mm

@@ -16,12 +16,11 @@
 
 PipelineLibraryMTL::~PipelineLibraryMTL() = default;
 
-// TODO(csg): Make PipelineDescriptor a struct and move this to formats_mtl.
 static MTLRenderPipelineDescriptor* GetMTLRenderPipelineDescriptor(
     const PipelineDescriptor& desc) {
   auto descriptor = [[MTLRenderPipelineDescriptor alloc] init];
   descriptor.label = @(desc.GetLabel().c_str());
-  descriptor.sampleCount = desc.GetSampleCount();
+  descriptor.sampleCount = static_cast<NSUInteger>(desc.GetSampleCount());
 
   for (const auto& entry : desc.GetStageEntrypoints()) {
     if (entry.first == ShaderStage::kVertex) {
@@ -53,8 +52,6 @@
   descriptor.stencilAttachmentPixelFormat =
       ToMTLPixelFormat(desc.GetStencilPixelFormat());
 
-  descriptor.sampleCount = 4u;
-
   return descriptor;
 }
 

impeller/renderer/backend/metal/render_pass_mtl.mm

@@ -388,6 +388,8 @@ static bool Bind(PassBindingsCache& pass,
     return true;
   };
 
+  const auto target_sample_count = render_target_.GetSampleCount();
+
   fml::closure pop_debug_marker = [encoder]() { [encoder popDebugGroup]; };
   for (const auto& command : commands_) {
     if (command.index_count == 0u) {
@@ -401,6 +403,14 @@ static bool Bind(PassBindingsCache& pass,
     } else {
       auto_pop_debug_marker.Release();
     }
+
+    if (target_sample_count !=
+        command.pipeline->GetDescriptor().GetSampleCount()) {
+      VALIDATION_LOG << "Pipeline for command and the render target disagree "
+                        "on sample counts.";
+      return false;
+    }
+
     pass_bindings.SetRenderPipelineState(
         PipelineMTL::Cast(*command.pipeline).GetMTLRenderPipelineState());
     pass_bindings.SetDepthStencilState(
@@ -447,6 +457,7 @@ static bool Bind(PassBindingsCache& pass,
 
 bool RenderPassMTL::AddCommand(Command command) {
   if (!command) {
+    VALIDATION_LOG << "Attempted to add an invalid command to the render pass.";
     return false;
   }
 

impeller/renderer/pipeline_builder.h

@@ -69,10 +69,10 @@ struct PipelineBuilder {
           FragmentShader::kEntrypointName, ShaderStage::kFragment);
 
       if (!vertex_function || !fragment_function) {
-        FML_LOG(ERROR) << "Could not resolve pipeline entrypoint(s) '"
+        VALIDATION_LOG << "Could not resolve pipeline entrypoint(s) '"
                        << VertexShader::kEntrypointName << "' and '"
                        << FragmentShader::kEntrypointName
-                       << "' for pipline named '" << VertexShader::kLabel
+                       << "' for pipeline named '" << VertexShader::kLabel
                        << "'.";
         return false;
       }
@@ -86,7 +86,7 @@ struct PipelineBuilder {
       auto vertex_descriptor = std::make_shared<VertexDescriptor>();
       if (!vertex_descriptor->SetStageInputs(
               VertexShader::kAllShaderStageInputs)) {
-        FML_LOG(ERROR)
+        VALIDATION_LOG
             << "Could not configure vertex descriptor for pipeline named '"
             << VertexShader::kLabel << "'.";
         return false;

impeller/renderer/pipeline_descriptor.cc

@@ -61,7 +61,7 @@ PipelineDescriptor& PipelineDescriptor::SetLabel(std::string label) {
   return *this;
 }
 
-PipelineDescriptor& PipelineDescriptor::SetSampleCount(size_t samples) {
+PipelineDescriptor& PipelineDescriptor::SetSampleCount(SampleCount samples) {
   sample_count_ = samples;
   return *this;
 }

impeller/renderer/pipeline_descriptor.h

@@ -32,9 +32,9 @@ class PipelineDescriptor final : public Comparable<PipelineDescriptor> {
 
   const std::string& GetLabel() const;
 
-  PipelineDescriptor& SetSampleCount(size_t samples);
+  PipelineDescriptor& SetSampleCount(SampleCount samples);
 
-  size_t GetSampleCount() const { return sample_count_; }
+  SampleCount GetSampleCount() const { return sample_count_; }
 
   PipelineDescriptor& AddStageEntrypoint(
       std::shared_ptr<const ShaderFunction> function);
@@ -97,7 +97,7 @@ class PipelineDescriptor final : public Comparable<PipelineDescriptor> {
 
  private:
   std::string label_;
-  size_t sample_count_ = 1;
+  SampleCount sample_count_ = SampleCount::kCount1;
   std::map<ShaderStage, std::shared_ptr<const ShaderFunction>> entrypoints_;
   std::map<size_t /* index */, ColorAttachmentDescriptor>
       color_attachment_descriptors_;

impeller/renderer/render_target.cc

@@ -101,6 +101,13 @@ void RenderTarget::IterateAllAttachments(
   }
 }
 
+SampleCount RenderTarget::GetSampleCount() const {
+  if (auto found = colors_.find(0u); found != colors_.end()) {
+    return found->second.texture->GetTextureDescriptor().sample_count;
+  }
+  return SampleCount::kCount1;
+}
+
 bool RenderTarget::HasColorAttachment(size_t index) const {
   if (auto found = colors_.find(index); found != colors_.end()) {
     return true;

impeller/renderer/render_target.h

@@ -22,12 +22,18 @@ class RenderTarget {
                                       ISize size,
                                       std::string label = "Offscreen");
 
+  static RenderTarget CreateMSAA(const Context& context,
+                                 std::shared_ptr<Texture> resolve_texture,
+                                 std::string label = "Offscreen");
+
   RenderTarget();
 
   ~RenderTarget();
 
   bool IsValid() const;
 
+  SampleCount GetSampleCount() const;
+
   bool HasColorAttachment(size_t index) const;
 
   ISize GetRenderTargetSize() const;