render_pass.h

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// Copyright 2013 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
 
#ifndef FLUTTER_IMPELLER_RENDERER_RENDER_PASS_H_
#define FLUTTER_IMPELLER_RENDERER_RENDER_PASS_H_
 
#include <cstddef>
 
#include "fml/status.h"
#include "impeller/core/formats.h"
#include "impeller/core/resource_binder.h"
#include "impeller/core/shader_types.h"
#include "impeller/core/vertex_buffer.h"
#include "impeller/renderer/command.h"
#include "impeller/renderer/command_buffer.h"
#include "impeller/renderer/render_target.h"
 
namespace impeller {
 
//------------------------------------------------------------------------------
/// @brief      Render passes encode render commands directed as one specific
///             render target into an underlying command buffer.
///
///             Render passes can be obtained from the command buffer in which
///             the pass is meant to encode commands into.
///
/// @see        `CommandBuffer`
///
class RenderPass : public ResourceBinder {
 public:
  virtual ~RenderPass();
 
  const std::shared_ptr<const Context>& GetContext() const;
 
  const RenderTarget& GetRenderTarget() const;
 
  ISize GetRenderTargetSize() const;
 
  const Matrix& GetOrthographicTransform() const;
 
  virtual bool IsValid() const = 0;
 
  void SetLabel(std::string_view label);
 
  //----------------------------------------------------------------------------
  /// The pipeline to use for this command.
  virtual void SetPipeline(PipelineRef pipeline);
 
  //----------------------------------------------------------------------------
  /// The pipeline to use for this command.
  void SetPipeline(
      const std::shared_ptr<Pipeline<PipelineDescriptor>>& pipeline);
 
  //----------------------------------------------------------------------------
  /// The debugging label to use for the command.
  virtual void SetCommandLabel(std::string_view label);
 
  //----------------------------------------------------------------------------
  /// The reference value to use in stenciling operations. Stencil configuration
  /// is part of pipeline setup and can be read from the pipelines descriptor.
  ///
  /// @see         `Pipeline`
  /// @see         `PipelineDescriptor`
  ///
  virtual void SetStencilReference(uint32_t value);
 
  virtual void SetBaseVertex(uint64_t value);
 
  //----------------------------------------------------------------------------
  /// The viewport coordinates that the rasterizer linearly maps normalized
  /// device coordinates to.
  /// If unset, the viewport is the size of the render target with a zero
  /// origin, znear=0, and zfar=1.
  ///
  virtual void SetViewport(Viewport viewport);
 
  //----------------------------------------------------------------------------
  /// The scissor rect to use for clipping writes to the render target. The
  /// scissor rect must lie entirely within the render target.
  /// If unset, no scissor is applied.
  ///
  virtual void SetScissor(IRect32 scissor);
 
  //----------------------------------------------------------------------------
  /// The number of elements to draw. When only a vertex buffer is set, this is
  /// the vertex count. When an index buffer is set, this is the index count.
  ///
  virtual void SetElementCount(size_t count);
 
  //----------------------------------------------------------------------------
  /// The number of instances of the given set of vertices to render. Not all
  /// backends support rendering more than one instance at a time.
  ///
  /// @warning      Setting this to more than one will limit the availability of
  ///               backends to use with this command.
  ///
  virtual void SetInstanceCount(size_t count);
 
  //----------------------------------------------------------------------------
  /// @deprecated Use SetVertexBuffer(BufferView[], size_t, size_t) instead.
  ///
  /// @brief      Specify the vertex and index buffer to use for this command.
  ///
  /// @param[in]  buffer  The vertex and index buffer definition. If possible,
  ///             this value should be moved and not copied.
  ///
  /// @return     returns if the binding was updated.
  ///
  virtual bool SetVertexBuffer(VertexBuffer buffer);
 
  //----------------------------------------------------------------------------
  /// @brief      Specify a vertex buffer to use for this command.
  ///
  /// @param[in]  vertex_buffer  The buffer view to use for sourcing vertices.
  ///
  /// @return     Returns false if the given buffer view is invalid.
  ///
  bool SetVertexBuffer(BufferView vertex_buffer);
 
  //----------------------------------------------------------------------------
  /// @brief      Specify a set of vertex buffers to use for this command.
  ///
  /// @warning    This method takes ownership of each buffer view in the vector.
  ///             Attempting to use the given buffer views after this call is
  ///             invalid.
  ///
  /// @param[in]  vertex_buffers  The array of vertex buffer views to use.
  ///                             The maximum number of vertex buffers is 16.
  ///
  /// @return     Returns false if any of the given buffer views are invalid.
  ///
  bool SetVertexBuffer(std::vector<BufferView> vertex_buffers);
 
  //----------------------------------------------------------------------------
  /// @brief      Specify a set of vertex buffers to use for this command.
  ///
  /// @warning    This method takes ownership of each buffer view in the vector.
  ///             Attempting to use the given buffer views after this call is
  ///             invalid.
  ///
  /// @param[in]  vertex_buffers      Pointer to an array of vertex buffers to
  ///                                 be copied. The maximum number of vertex
  ///                                 buffers is 16.
  ///
  /// @param[in]  vertex_buffer_count The number of vertex buffers to copy from
  ///                                 the array (max 16).
  ///
  /// @return     Returns false if any of the given buffer views are invalid.
  ///
  virtual bool SetVertexBuffer(BufferView vertex_buffers[],
                               size_t vertex_buffer_count);
 
  //----------------------------------------------------------------------------
  /// @brief      Specify an index buffer to use for this command.
  ///             To unset the index buffer, pass IndexType::kNone to
  ///             index_type.
  ///
  /// @param[in]  index_buffer  The buffer view to use for sourcing indices.
  ///                           When an index buffer is bound, the
  ///                           `vertex_count` set via `SetVertexBuffer` is used
  ///                           as the number of indices to draw.
  ///
  /// @param[in]  index_type    The size of each index in the index buffer. Pass
  ///                           IndexType::kNone to unset the index buffer.
  ///
  /// @return     Returns false if the index buffer view is invalid.
  ///
  virtual bool SetIndexBuffer(BufferView index_buffer, IndexType index_type);
 
  /// Record the currently pending command.
  virtual fml::Status Draw();
 
  // |ResourceBinder|
  virtual bool BindResource(ShaderStage stage,
                            DescriptorType type,
                            const ShaderUniformSlot& slot,
                            const ShaderMetadata* metadata,
                            BufferView view) override;
 
  // |ResourceBinder|
  virtual bool BindResource(ShaderStage stage,
                            DescriptorType type,
                            const SampledImageSlot& slot,
                            const ShaderMetadata* metadata,
                            std::shared_ptr<const Texture> texture,
                            raw_ptr<const Sampler>) override;
 
  /// @brief Bind with dynamically generated shader metadata.
  virtual bool BindDynamicResource(ShaderStage stage,
                                   DescriptorType type,
                                   const SampledImageSlot& slot,
                                   std::unique_ptr<ShaderMetadata> metadata,
                                   std::shared_ptr<const Texture> texture,
                                   raw_ptr<const Sampler>);
 
  /// @brief Bind with dynamically generated shader metadata.
  virtual bool BindDynamicResource(ShaderStage stage,
                                   DescriptorType type,
                                   const ShaderUniformSlot& slot,
                                   std::unique_ptr<ShaderMetadata> metadata,
                                   BufferView view);
 
  //----------------------------------------------------------------------------
  /// @brief      Encode the recorded commands to the underlying command buffer.
  ///
  /// @return     If the commands were encoded to the underlying command
  ///             buffer.
  ///
  bool EncodeCommands() const;
 
  //----------------------------------------------------------------------------
  /// @brief      Accessor for the current Commands.
  ///
  /// @details    Visible for testing.
  ///
  virtual const std::vector<Command>& GetCommands() const { return commands_; }
 
  //----------------------------------------------------------------------------
  /// @brief      The sample count of the attached render target.
  SampleCount GetSampleCount() const;
 
  //----------------------------------------------------------------------------
  /// @brief      The pixel format of the attached render target.
  PixelFormat GetRenderTargetPixelFormat() const;
 
  //----------------------------------------------------------------------------
  /// @brief      Whether the render target has a depth attachment.
  bool HasDepthAttachment() const;
 
  //----------------------------------------------------------------------------
  /// @brief      Whether the render target has an stencil attachment.
  bool HasStencilAttachment() const;
 
 protected:
  const std::shared_ptr<const Context> context_;
  // The following properties: sample_count, pixel_format,
  // has_stencil_attachment, and render_target_size are cached on the
  // RenderTarget to speed up numerous lookups during rendering. This is safe as
  // the RenderTarget itself is copied into the RenderTarget and only exposed as
  // a const reference.
  const SampleCount sample_count_;
  const PixelFormat pixel_format_;
  const bool has_depth_attachment_;
  const bool has_stencil_attachment_;
  const ISize render_target_size_;
  const RenderTarget render_target_;
  std::vector<Command> commands_;
  std::vector<BufferView> vertex_buffers_;
  std::vector<BufferResource> bound_buffers_;
  std::vector<TextureAndSampler> bound_textures_;
  const Matrix orthographic_;
 
  //----------------------------------------------------------------------------
  /// @brief      Record a command for subsequent encoding to the underlying
  ///             command buffer. No work is encoded into the command buffer at
  ///             this time.
  ///
  /// @param[in]  command  The command
  ///
  /// @return     If the command was valid for subsequent commitment.
  ///
  bool AddCommand(Command&& command);
 
  RenderPass(std::shared_ptr<const Context> context,
             const RenderTarget& target);
 
  static bool ValidateVertexBuffers(const BufferView vertex_buffers[],
                                    size_t vertex_buffer_count);
 
  static bool ValidateIndexBuffer(const BufferView& index_buffer,
                                  IndexType index_type);
 
  virtual void OnSetLabel(std::string_view label) = 0;
 
  virtual bool OnEncodeCommands(const Context& context) const = 0;
 
 private:
  RenderPass(const RenderPass&) = delete;
 
  RenderPass& operator=(const RenderPass&) = delete;
 
  bool BindBuffer(ShaderStage stage,
                  const ShaderUniformSlot& slot,
                  BufferResource resource);
 
  bool BindTexture(ShaderStage stage,
                   const SampledImageSlot& slot,
                   TextureResource resource,
                   raw_ptr<const Sampler>);
 
  Command pending_;
  std::optional<size_t> bound_buffers_start_ = std::nullopt;
  std::optional<size_t> bound_textures_start_ = std::nullopt;
  std::optional<size_t> vertex_buffers_start_ = std::nullopt;
};
 
}  // namespace impeller
 
#endif  // FLUTTER_IMPELLER_RENDERER_RENDER_PASS_H_