Minor fixups to pipeline creation.

Author: chinmaygarde

impeller/renderer/pipeline_builder.h

@@ -48,7 +48,16 @@ struct PipelineBuilder {
   static std::optional<PipelineDescriptor> MakeDefaultPipelineDescriptor(
       const Context& context) {
     PipelineDescriptor desc;
+    if (InitializePipelineDescriptorDefaults(context, desc)) {
+      return {std::move(desc)};
+    } else {
+      return std::nullopt;
+    }
+  }
 
+  [[nodiscard]] static bool InitializePipelineDescriptorDefaults(
+      const Context& context,
+      PipelineDescriptor& desc) {
     // Setup debug instrumentation.
     desc.SetLabel(SPrintF("%s Pipeline", VertexShader::kLabel.data()));
 
@@ -61,7 +70,7 @@ struct PipelineBuilder {
 
       if (!vertex_function || !fragment_function) {
         FML_LOG(ERROR) << "Could not resolve pipeline entrypoint(s).";
-        return std::nullopt;
+        return false;
       }
 
       desc.AddStageEntrypoint(std::move(vertex_function));
@@ -74,35 +83,22 @@ struct PipelineBuilder {
       if (!vertex_descriptor->SetStageInputs(
               VertexShader::kAllShaderStageInputs)) {
         FML_LOG(ERROR) << "Could not configure vertex descriptor.";
-        return std::nullopt;
+        return false;
       }
       desc.SetVertexDescriptor(std::move(vertex_descriptor));
     }
 
     // Setup fragment shader output descriptions.
     {
-      // Configure the sole color attachments pixel format.
-      // TODO(csg): This can be easily reflected but we are sticking to the
-      // convention that the first stage output is the color output.
+      // Configure the sole color attachments pixel format. This is by
+      // convention.
       ColorAttachmentDescriptor color0;
       color0.format = PixelFormat::kB8G8R8A8UNormInt;
       color0.blending_enabled = true;
       desc.SetColorAttachmentDescriptor(0u, std::move(color0));
     }
 
-    // Setup depth and stencil attachment descriptions.
-    {
-      // Configure the stencil attachment.
-      // TODO(csg): Make this configurable if possible as the D32 component is
-      // wasted. This can even be moved out of the "default" descriptor
-      // construction as a case can be made that this is caller responsibility.
-      // const auto combined_depth_stencil_format =
-      //     PixelFormat::kPixelFormat_D32_Float_S8_UNormInt;
-      // desc.SetDepthPixelFormat(combined_depth_stencil_format);
-      // desc.SetStencilPixelFormat(combined_depth_stencil_format);
-    }
-
-    return desc;
+    return true;
   }
 };
 

impeller/renderer/pipeline_descriptor.cc

@@ -132,4 +132,53 @@ PipelineDescriptor& PipelineDescriptor::SetStencilAttachmentDescriptors(
   return *this;
 }
 
+void PipelineDescriptor::ResetAttachments() {
+  color_attachment_descriptors_.clear();
+  depth_attachment_descriptor_.reset();
+  front_stencil_attachment_descriptor_.reset();
+  back_stencil_attachment_descriptor_.reset();
+}
+
+PixelFormat PipelineDescriptor::GetStencilPixelFormat() const {
+  return stencil_pixel_format_;
+}
+
+std::optional<StencilAttachmentDescriptor>
+PipelineDescriptor::GetFrontStencilAttachmentDescriptor() const {
+  return front_stencil_attachment_descriptor_;
+}
+
+std::optional<DepthAttachmentDescriptor>
+PipelineDescriptor::GetDepthStencilAttachmentDescriptor() const {
+  return depth_attachment_descriptor_;
+}
+
+const std::map<size_t /* index */, ColorAttachmentDescriptor>
+PipelineDescriptor::GetColorAttachmentDescriptors() const {
+  return color_attachment_descriptors_;
+}
+
+const std::shared_ptr<VertexDescriptor>&
+PipelineDescriptor::GetVertexDescriptor() const {
+  return vertex_descriptor_;
+}
+
+const std::map<ShaderStage, std::shared_ptr<const ShaderFunction>>&
+PipelineDescriptor::GetStageEntrypoints() const {
+  return entrypoints_;
+}
+
+const std::string& PipelineDescriptor::GetLabel() const {
+  return label_;
+}
+
+PixelFormat PipelineDescriptor::GetDepthPixelFormat() const {
+  return depth_pixel_format_;
+}
+
+std::optional<StencilAttachmentDescriptor>
+PipelineDescriptor::GetBackStencilAttachmentDescriptor() const {
+  return back_stencil_attachment_descriptor_;
+}
+
 }  // namespace impeller

impeller/renderer/pipeline_descriptor.h

@@ -30,7 +30,7 @@ class PipelineDescriptor final : public Comparable<PipelineDescriptor> {
 
   PipelineDescriptor& SetLabel(std::string label);
 
-  const std::string& GetLabel() const { return label_; }
+  const std::string& GetLabel() const;
 
   PipelineDescriptor& SetSampleCount(size_t samples);
 
@@ -40,16 +40,12 @@ class PipelineDescriptor final : public Comparable<PipelineDescriptor> {
       std::shared_ptr<const ShaderFunction> function);
 
   const std::map<ShaderStage, std::shared_ptr<const ShaderFunction>>&
-  GetStageEntrypoints() const {
-    return entrypoints_;
-  }
+  GetStageEntrypoints() const;
 
   PipelineDescriptor& SetVertexDescriptor(
       std::shared_ptr<VertexDescriptor> vertex_descriptor);
 
-  const std::shared_ptr<VertexDescriptor>& GetVertexDescriptor() const {
-    return vertex_descriptor_;
-  }
+  const std::shared_ptr<VertexDescriptor>& GetVertexDescriptor() const;
 
   PipelineDescriptor& SetColorAttachmentDescriptor(
       size_t index,
@@ -59,17 +55,13 @@ class PipelineDescriptor final : public Comparable<PipelineDescriptor> {
       size_t index) const;
 
   const std::map<size_t /* index */, ColorAttachmentDescriptor>
-  GetColorAttachmentDescriptors() const {
-    return color_attachment_descriptors_;
-  }
+  GetColorAttachmentDescriptors() const;
 
   PipelineDescriptor& SetDepthStencilAttachmentDescriptor(
       DepthAttachmentDescriptor desc);
 
   std::optional<DepthAttachmentDescriptor> GetDepthStencilAttachmentDescriptor()
-      const {
-    return depth_attachment_descriptor_;
-  }
+      const;
 
   PipelineDescriptor& SetStencilAttachmentDescriptors(
       StencilAttachmentDescriptor front_and_back);
@@ -79,29 +71,27 @@ class PipelineDescriptor final : public Comparable<PipelineDescriptor> {
       StencilAttachmentDescriptor back);
 
   std::optional<StencilAttachmentDescriptor>
-  GetFrontStencilAttachmentDescriptor() const {
-    return front_stencil_attachment_descriptor_;
-  }
+  GetFrontStencilAttachmentDescriptor() const;
 
   std::optional<StencilAttachmentDescriptor>
-  GetBackStencilAttachmentDescriptor() const {
-    return back_stencil_attachment_descriptor_;
-  }
+  GetBackStencilAttachmentDescriptor() const;
 
   PipelineDescriptor& SetDepthPixelFormat(PixelFormat format);
 
-  PixelFormat GetDepthPixelFormat() const { return depth_pixel_format_; }
+  PixelFormat GetDepthPixelFormat() const;
 
   PipelineDescriptor& SetStencilPixelFormat(PixelFormat format);
 
-  PixelFormat GetStencilPixelFormat() const { return stencil_pixel_format_; }
+  PixelFormat GetStencilPixelFormat() const;
 
   // Comparable<PipelineDescriptor>
   std::size_t GetHash() const override;
 
   // Comparable<PipelineDescriptor>
   bool IsEqual(const PipelineDescriptor& other) const override;
 
+  void ResetAttachments();
+
  private:
   std::string label_;
   size_t sample_count_ = 1;