entity_pass_target.cc

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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.
 
#include "impeller/entity/entity_pass_target.h"
 
#include "impeller/base/validation.h"
#include "impeller/core/formats.h"
#include "impeller/core/texture.h"
 
namespace impeller {
 
EntityPassTarget::EntityPassTarget(const RenderTarget& render_target,
                                   bool supports_read_from_resolve,
                                   bool supports_implicit_msaa)
    : target_(render_target),
      supports_read_from_resolve_(supports_read_from_resolve),
      supports_implicit_msaa_(supports_implicit_msaa) {}
 
std::shared_ptr<Texture> EntityPassTarget::Flip(
    const ContentContext& renderer) {
  ColorAttachment color0 = target_.GetColorAttachment(0);
  if (!color0.resolve_texture) {
    VALIDATION_LOG << "EntityPassTarget Flip should never be called for a "
                      "non-MSAA target.";
    // ...because there is never a circumstance where doing so would be
    // necessary. Unlike MSAA passes, non-MSAA passes can be trivially loaded
    // with `LoadAction::kLoad`.
    return color0.texture;
  }
 
  if (supports_read_from_resolve_) {
    // Just return the current resolve texture, which is safe to read in the
    // next render pass that'll resolve to `target_`.
    //
    // Note that this can only be done when MSAA is being used.
    return color0.resolve_texture;
  }
 
  if (!secondary_color_texture_) {
    // The second texture is allocated lazily to avoid unused allocations.
    TextureDescriptor new_descriptor =
        color0.resolve_texture->GetTextureDescriptor();
    RenderTarget target = renderer.GetRenderTargetCache()->CreateOffscreenMSAA(
        *renderer.GetContext(), new_descriptor.size, 1);
    secondary_color_texture_ = target.GetRenderTargetTexture();
 
    if (!secondary_color_texture_) {
      return nullptr;
    }
  }
 
  // If the color0 resolve texture is the same as the texture, then we're
  // running on the GLES backend with implicit resolve.
  if (supports_implicit_msaa_) {
    auto new_secondary = color0.resolve_texture;
    color0.resolve_texture = secondary_color_texture_;
    color0.texture = secondary_color_texture_;
    secondary_color_texture_ = new_secondary;
  } else {
    std::swap(color0.resolve_texture, secondary_color_texture_);
  }
 
  target_.SetColorAttachment(color0, 0);
 
  // Return the previous backdrop texture, which is safe to read in the next
  // render pass that attaches `target_`.
  return secondary_color_texture_;
}
 
RenderTarget& EntityPassTarget::GetRenderTarget() {
  return target_;
}
 
bool EntityPassTarget::IsValid() const {
  return target_.IsValid();
}
 
void EntityPassTarget::RemoveSecondary() {
  secondary_color_texture_ = nullptr;
}
 
}  // namespace impeller