impeller/entity/contents/filters/blend_filter_contents.cc

// 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.

#include "impeller/entity/contents/filters/blend_filter_contents.h"

#include <array>
#include <memory>
#include <optional>

#include "impeller/entity/contents/content_context.h"
#include "impeller/entity/contents/contents.h"
#include "impeller/entity/contents/filters/inputs/filter_input.h"
#include "impeller/entity/contents/solid_color_contents.h"
#include "impeller/entity/entity.h"
#include "impeller/geometry/path_builder.h"
#include "impeller/renderer/render_pass.h"
#include "impeller/renderer/sampler_library.h"

namespace impeller {

BlendFilterContents::BlendFilterContents() {
  SetBlendMode(BlendMode::kSourceOver);
}

BlendFilterContents::~BlendFilterContents() = default;

using PipelineProc = std::shared_ptr<Pipeline<PipelineDescriptor>> (
    ContentContext::*)(ContentContextOptions) const;

template <typename TPipeline>
static std::optional<Snapshot> AdvancedBlend(
    const FilterInput::Vector& inputs,
    const ContentContext& renderer,
    const Entity& entity,
    const Rect& coverage,
    std::optional<Color> foreground_color,
    bool absorb_opacity,
    PipelineProc pipeline_proc) {
  using VS = typename TPipeline::VertexShader;
  using FS = typename TPipeline::FragmentShader;

  //----------------------------------------------------------------------------
  /// Handle inputs.
  ///

  const size_t total_inputs =
      inputs.size() + (foreground_color.has_value() ? 1 : 0);
  if (total_inputs < 2) {
    return std::nullopt;
  }

  auto dst_snapshot = inputs[0]->GetSnapshot(renderer, entity);
  if (!dst_snapshot.has_value()) {
    return std::nullopt;
  }
  auto maybe_dst_uvs = dst_snapshot->GetCoverageUVs(coverage);
  if (!maybe_dst_uvs.has_value()) {
    return std::nullopt;
  }
  auto dst_uvs = maybe_dst_uvs.value();

  std::optional<Snapshot> src_snapshot;
  std::array<Point, 4> src_uvs;
  if (!foreground_color.has_value()) {
    src_snapshot = inputs[1]->GetSnapshot(renderer, entity);
    if (!src_snapshot.has_value()) {
      return dst_snapshot;
    }
    auto maybe_src_uvs = src_snapshot->GetCoverageUVs(coverage);
    if (!maybe_src_uvs.has_value()) {
      return dst_snapshot;
    }
    src_uvs = maybe_src_uvs.value();
  }

  //----------------------------------------------------------------------------
  /// Render to texture.
  ///

  ContentContext::SubpassCallback callback = [&](const ContentContext& renderer,
                                                 RenderPass& pass) {
    auto& host_buffer = pass.GetTransientsBuffer();

    auto size = pass.GetRenderTargetSize();
    VertexBufferBuilder<typename VS::PerVertexData> vtx_builder;
    vtx_builder.AddVertices({
        {Point(0, 0), dst_uvs[0], src_uvs[0]},
        {Point(size.width, 0), dst_uvs[1], src_uvs[1]},
        {Point(size.width, size.height), dst_uvs[3], src_uvs[3]},
        {Point(0, 0), dst_uvs[0], src_uvs[0]},
        {Point(size.width, size.height), dst_uvs[3], src_uvs[3]},
        {Point(0, size.height), dst_uvs[2], src_uvs[2]},
    });
    auto vtx_buffer = vtx_builder.CreateVertexBuffer(host_buffer);

    auto options = OptionsFromPass(pass);
    options.blend_mode = BlendMode::kSource;
    std::shared_ptr<Pipeline<PipelineDescriptor>> pipeline =
        std::invoke(pipeline_proc, renderer, options);

    Command cmd;
    cmd.label = "Advanced Blend Filter";
    cmd.BindVertices(vtx_buffer);
    cmd.pipeline = std::move(pipeline);

    typename FS::BlendInfo blend_info;

    auto sampler = renderer.GetContext()->GetSamplerLibrary()->GetSampler({});
    FS::BindTextureSamplerDst(cmd, dst_snapshot->texture, sampler);
    blend_info.dst_y_coord_scale = dst_snapshot->texture->GetYCoordScale();
    blend_info.dst_input_alpha = absorb_opacity ? dst_snapshot->opacity : 1.0f;

    if (foreground_color.has_value()) {
      blend_info.color_factor = 1;
      blend_info.color = foreground_color.value();
      // This texture will not be sampled from due to the color factor. But
      // this is present so that validation doesn't trip on a missing
      // binding.
      FS::BindTextureSamplerSrc(cmd, dst_snapshot->texture, sampler);
    } else {
      blend_info.color_factor = 0;
      FS::BindTextureSamplerSrc(cmd, src_snapshot->texture, sampler);
      blend_info.src_y_coord_scale = src_snapshot->texture->GetYCoordScale();
    }
    auto blend_uniform = host_buffer.EmplaceUniform(blend_info);
    FS::BindBlendInfo(cmd, blend_uniform);

    typename VS::FrameInfo frame_info;
    frame_info.mvp = Matrix::MakeOrthographic(size);

    auto uniform_view = host_buffer.EmplaceUniform(frame_info);
    VS::BindFrameInfo(cmd, uniform_view);
    pass.AddCommand(cmd);

    return true;
  };

  auto out_texture = renderer.MakeSubpass(ISize(coverage.size), callback);
  if (!out_texture) {
    return std::nullopt;
  }
  out_texture->SetLabel("Advanced Blend Filter Texture");

  return Snapshot{.texture = out_texture,
                  .transform = Matrix::MakeTranslation(coverage.origin),
                  .sampler_descriptor = dst_snapshot->sampler_descriptor,
                  .opacity = absorb_opacity ? 1.0f : dst_snapshot->opacity};
}

static std::optional<Snapshot> PipelineBlend(
    const FilterInput::Vector& inputs,
    const ContentContext& renderer,
    const Entity& entity,
    const Rect& coverage,
    BlendMode pipeline_blend,
    std::optional<Color> foreground_color,
    bool absorb_opacity) {
  using VS = BlendPipeline::VertexShader;
  using FS = BlendPipeline::FragmentShader;

  auto input_snapshot = inputs[0]->GetSnapshot(renderer, entity);

  ContentContext::SubpassCallback callback = [&](const ContentContext& renderer,
                                                 RenderPass& pass) {
    auto& host_buffer = pass.GetTransientsBuffer();

    auto sampler = renderer.GetContext()->GetSamplerLibrary()->GetSampler({});

    Command cmd;
    cmd.label = "Pipeline Blend Filter";
    auto options = OptionsFromPass(pass);

    auto add_blend_command = [&](std::optional<Snapshot> input) {
      if (!input.has_value()) {
        return false;
      }
      auto input_coverage = input->GetCoverage();
      if (!input_coverage.has_value()) {
        return false;
      }

      FS::BindTextureSamplerSrc(cmd, input->texture, sampler);

      auto size = input->texture->GetSize();
      VertexBufferBuilder<VS::PerVertexData> vtx_builder;
      vtx_builder.AddVertices({
          {Point(0, 0), Point(0, 0)},
          {Point(size.width, 0), Point(1, 0)},
          {Point(size.width, size.height), Point(1, 1)},
          {Point(0, 0), Point(0, 0)},
          {Point(size.width, size.height), Point(1, 1)},
          {Point(0, size.height), Point(0, 1)},
      });
      auto vtx_buffer = vtx_builder.CreateVertexBuffer(host_buffer);
      cmd.BindVertices(vtx_buffer);

      VS::FrameInfo frame_info;
      frame_info.mvp = Matrix::MakeOrthographic(pass.GetRenderTargetSize()) *
                       Matrix::MakeTranslation(-coverage.origin) *
                       input->transform;
      FS::FragInfo frag_info;
      frag_info.texture_sampler_y_coord_scale =
          input->texture->GetYCoordScale();
      frag_info.input_alpha = absorb_opacity ? input->opacity : 1.0f;
      FS::BindFragInfo(cmd, host_buffer.EmplaceUniform(frag_info));
      VS::BindFrameInfo(cmd, host_buffer.EmplaceUniform(frame_info));

      pass.AddCommand(cmd);
      return true;
    };

    // Draw the first texture using kSource.
    options.blend_mode = BlendMode::kSource;
    cmd.pipeline = renderer.GetBlendPipeline(options);
    if (!add_blend_command(input_snapshot)) {
      return true;
    }

    // Write subsequent textures using the selected blend mode.

    if (inputs.size() >= 2) {
      options.blend_mode = pipeline_blend;
      cmd.pipeline = renderer.GetBlendPipeline(options);

      for (auto texture_i = inputs.begin() + 1; texture_i < inputs.end();
           texture_i++) {
        auto input = texture_i->get()->GetSnapshot(renderer, entity);
        if (!add_blend_command(input)) {
          return true;
        }
      }
    }

    // If a foreground color is set, blend it in.

    if (foreground_color.has_value()) {
      auto contents = std::make_shared<SolidColorContents>();
      contents->SetGeometry(Geometry::MakeFillPath(
          PathBuilder{}
              .AddRect(Rect::MakeSize(pass.GetRenderTargetSize()))
              .TakePath()));
      contents->SetColor(foreground_color.value());

      Entity foreground_entity;
      foreground_entity.SetBlendMode(pipeline_blend);
      foreground_entity.SetContents(contents);
      if (!foreground_entity.Render(renderer, pass)) {
        return false;
      }
    }

    return true;
  };

  auto out_texture = renderer.MakeSubpass(ISize(coverage.size), callback);
  if (!out_texture) {
    return std::nullopt;
  }
  out_texture->SetLabel("Pipeline Blend Filter Texture");

  return Snapshot{
      .texture = out_texture,
      .transform = Matrix::MakeTranslation(coverage.origin),
      .sampler_descriptor =
          inputs[0]->GetSnapshot(renderer, entity)->sampler_descriptor,
      .opacity = absorb_opacity ? 1.0f : input_snapshot->opacity};
}

#define BLEND_CASE(mode)                                                    \
  case BlendMode::k##mode:                                                  \
    advanced_blend_proc_ = [](const FilterInput::Vector& inputs,            \
                              const ContentContext& renderer,               \
                              const Entity& entity, const Rect& coverage,   \
                              std::optional<Color> fg_color,                \
                              bool absorb_opacity) {                        \
      PipelineProc p = &ContentContext::GetBlend##mode##Pipeline;           \
      return AdvancedBlend<BlendScreenPipeline>(                            \
          inputs, renderer, entity, coverage, fg_color, absorb_opacity, p); \
    };                                                                      \
    break;

void BlendFilterContents::SetBlendMode(BlendMode blend_mode) {
  if (blend_mode > Entity::kLastAdvancedBlendMode) {
    VALIDATION_LOG << "Invalid blend mode " << static_cast<int>(blend_mode)
                   << " assigned to BlendFilterContents.";
  }

  blend_mode_ = blend_mode;

  if (blend_mode > Entity::kLastPipelineBlendMode) {
    switch (blend_mode) {
      BLEND_CASE(Screen)
      BLEND_CASE(Overlay)
      BLEND_CASE(Darken)
      BLEND_CASE(Lighten)
      BLEND_CASE(ColorDodge)
      BLEND_CASE(ColorBurn)
      BLEND_CASE(HardLight)
      BLEND_CASE(SoftLight)
      BLEND_CASE(Difference)
      BLEND_CASE(Exclusion)
      BLEND_CASE(Multiply)
      BLEND_CASE(Hue)
      BLEND_CASE(Saturation)
      BLEND_CASE(Color)
      BLEND_CASE(Luminosity)
      default:
        FML_UNREACHABLE();
    }
  }
}

void BlendFilterContents::SetForegroundColor(std::optional<Color> color) {
  foreground_color_ = color;
}

std::optional<Snapshot> BlendFilterContents::RenderFilter(
    const FilterInput::Vector& inputs,
    const ContentContext& renderer,
    const Entity& entity,
    const Matrix& effect_transform,
    const Rect& coverage) const {
  if (inputs.empty()) {
    return std::nullopt;
  }

  if (inputs.size() == 1 && !foreground_color_.has_value()) {
    // Nothing to blend.
    return PipelineBlend(inputs, renderer, entity, coverage, BlendMode::kSource,
                         std::nullopt, GetAbsorbOpacity());
  }

  if (blend_mode_ <= Entity::kLastPipelineBlendMode) {
    return PipelineBlend(inputs, renderer, entity, coverage, blend_mode_,
                         foreground_color_, GetAbsorbOpacity());
  }

  if (blend_mode_ <= Entity::kLastAdvancedBlendMode) {
    return advanced_blend_proc_(inputs, renderer, entity, coverage,
                                foreground_color_, GetAbsorbOpacity());
  }
  FML_UNREACHABLE();
}

}  // namespace impeller