filter_input.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.
 
#pragma once
 
#include <memory>
#include <optional>
#include <variant>
#include <vector>
 
#include "impeller/entity/contents/contents.h"
#include "impeller/entity/entity.h"
#include "impeller/geometry/rect.h"
 
namespace impeller {
 
class ContentContext;
class FilterContents;
 
/// `FilterInput` is a lazy/single eval `Snapshot` which may be shared across
/// filter parameters and used to evaluate input coverage.
///
/// A `FilterInput` can be re-used for any filter inputs across an entity's
/// filter graph without repeating subpasses unnecessarily.
///
/// Filters may decide to not evaluate inputs in situations where they won't
/// contribute to the filter's output texture.
class FilterInput {
 public:
  using Ref = std::shared_ptr<FilterInput>;
  using Vector = std::vector<FilterInput::Ref>;
  using Variant = std::variant<std::shared_ptr<FilterContents>,
                               std::shared_ptr<Contents>,
                               std::shared_ptr<Texture>,
                               Rect>;
 
  virtual ~FilterInput();
 
  static FilterInput::Ref Make(Variant input, bool msaa_enabled = true);
 
  static FilterInput::Ref Make(std::shared_ptr<Texture> input,
                               Matrix local_transform);
 
  static FilterInput::Vector Make(std::initializer_list<Variant> inputs);
 
  virtual Variant GetInput() const = 0;
 
  virtual std::optional<Snapshot> GetSnapshot(
      const std::string& label,
      const ContentContext& renderer,
      const Entity& entity,
      std::optional<Rect> coverage_limit = std::nullopt) const = 0;
 
  std::optional<Rect> GetLocalCoverage(const Entity& entity) const;
 
  virtual std::optional<Rect> GetCoverage(const Entity& entity) const = 0;
 
  /// @brief  Get the local transform of this filter input. This transform is
  ///         relative to the `Entity` transform space.
  virtual Matrix GetLocalTransform(const Entity& entity) const;
 
  /// @brief  Get the transform of this `FilterInput`. This is equivalent to
  ///         calling `entity.GetTransformation() * GetLocalTransform()`.
  virtual Matrix GetTransform(const Entity& entity) const;
 
  /// @see    `Contents::PopulateGlyphAtlas`
  virtual void PopulateGlyphAtlas(
      const std::shared_ptr<LazyGlyphAtlas>& lazy_glyph_atlas,
      Scalar scale);
 
  /// @see  `FilterContents::HasBasisTransformations`
  virtual bool IsTranslationOnly() const;
 
  /// @brief  Returns `true` unless this input is a `FilterInput`, which may
  ///         take other inputs.
  virtual bool IsLeaf() const;
 
  /// @brief  Replaces the inputs of all leaf `FilterContents` with a new set
  ///         of `inputs`.
  /// @see    `FilterInput::IsLeaf`
  virtual void SetLeafInputs(const FilterInput::Vector& inputs);
 
  /// @brief  Sets the effect transform of filter inputs.
  virtual void SetEffectTransform(const Matrix& matrix);
 
  /// @brief  Turns on subpass mode for filter inputs.
  virtual void SetRenderingMode(Entity::RenderingMode rendering_mode);
};
 
}  // namespace impeller