impeller/entity/contents/color_source_contents.h

// 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 "flutter/fml/macros.h"
#include "impeller/entity/contents/contents.h"
#include "impeller/entity/geometry/geometry.h"
#include "impeller/geometry/matrix.h"
#include "impeller/geometry/path.h"

namespace impeller {

//------------------------------------------------------------------------------
/// Color sources are geometry-ignostic `Contents` capable of shading any area
/// defined by an `impeller::Geometry`. Conceptually,
/// `impeller::ColorSourceContents` implement a particular color shading
/// behavior.
///
/// This separation of concerns between geometry and color source output allows
/// Impeller to handle most possible draw combinations in a consistent way.
/// For example: There are color sources for handling solid colors, gradients,
/// textures, custom runtime effects, and even 3D scenes.
///
/// There are some special rendering exceptions that deviate from this pattern
/// and cross geometry and color source concerns, such as text atlas and image
/// atlas rendering. Special `Contents` exist for rendering these behaviors
/// which don't implement `ColorSourceContents`.
///
/// @see  `impeller::Geometry`
///
class ColorSourceContents : public Contents {
 public:
  ColorSourceContents();

  ~ColorSourceContents() override;

  //----------------------------------------------------------------------------
  /// @brief  Set the geometry that this contents will use to render.
  ///
  void SetGeometry(std::shared_ptr<Geometry> geometry);

  //----------------------------------------------------------------------------
  /// @brief  Get the geometry that this contents will use to render.
  ///
  const std::shared_ptr<Geometry>& GetGeometry() const;

  //----------------------------------------------------------------------------
  /// @brief  Set the effect transform for this color source.
  ///
  ///         The effect transform is a transformation matrix that is applied to
  ///         the shaded color output and does not impact geometry in any way.
  ///
  ///         For example: With repeat tiling, any gradient or
  ///         `TiledTextureContents` could be used with an effect transform to
  ///         inexpensively draw an infinite scrolling background pattern.
  ///
  void SetEffectTransform(Matrix matrix);

  //----------------------------------------------------------------------------
  /// @brief   Set the inverted effect transform for this color source.
  ///
  ///          When the effect transform is set via `SetEffectTransform`, the
  ///          value is inverted upon storage. The reason for this is that most
  ///          color sources internally use the inverted transform.
  ///
  /// @return  The inverse of the transform set by `SetEffectTransform`.
  ///
  /// @see     `SetEffectTransform`
  ///
  const Matrix& GetInverseEffectTransform() const;

  //----------------------------------------------------------------------------
  /// @brief  Set the opacity factor for this color source.
  ///
  void SetOpacityFactor(Scalar opacity);

  //----------------------------------------------------------------------------
  /// @brief  Get the opacity factor for this color source.
  ///
  ///         This value is is factored into the output of the color source in
  ///         addition to opacity information that may be supplied any other
  ///         inputs.
  ///
  /// @note   If set, the output of this method factors factors in the inherited
  ///         opacity of this `Contents`.
  ///
  /// @see    `Contents::CanInheritOpacity`
  ///
  Scalar GetOpacityFactor() const;

  virtual bool IsSolidColor() const;

  // |Contents|
  std::optional<Rect> GetCoverage(const Entity& entity) const override;

  // |Contents|
  bool CanInheritOpacity(const Entity& entity) const override;

  // |Contents|
  void SetInheritedOpacity(Scalar opacity) override;

 private:
  std::shared_ptr<Geometry> geometry_;
  Matrix inverse_matrix_;
  Scalar opacity_ = 1.0;
  Scalar inherited_opacity_ = 1.0;

  FML_DISALLOW_COPY_AND_ASSIGN(ColorSourceContents);
};

}  // namespace impeller