impeller/entity/entity.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 <variant>
#include "impeller/entity/contents/contents.h"
#include "impeller/geometry/color.h"
#include "impeller/geometry/matrix.h"
#include "impeller/geometry/path.h"
#include "impeller/geometry/rect.h"
#include "impeller/image/decompressed_image.h"

namespace impeller {

class Renderer;
class RenderPass;

class Entity {
 public:
  /// All blend modes assume that both the source (fragment output) and
  /// destination (first color attachment) have colors with premultiplied alpha.
  enum class BlendMode {
    // The following blend modes are able to be used as pipeline blend modes or
    // via `BlendFilterContents`.
    kClear,
    kSource,
    kDestination,
    kSourceOver,
    kDestinationOver,
    kSourceIn,
    kDestinationIn,
    kSourceOut,
    kDestinationOut,
    kSourceATop,
    kDestinationATop,
    kXor,
    kPlus,
    kModulate,

    // The following blend modes use equations that are not available for
    // pipelines on most graphics devices without extensions, and so they are
    // only able to be used via `BlendFilterContents`.
    kScreen,
    kOverlay,
    kDarken,
    kLighten,
    kColorDodge,
    kColorBurn,
    kHardLight,
    kSoftLight,
    kDifference,
    kExclusion,
    kMultiply,
    kHue,
    kSaturation,
    kColor,
    kLuminosity,

    kLastPipelineBlendMode = kModulate,
    kLastAdvancedBlendMode = kLuminosity,
  };

  /// An enum to define how to repeat, fold, or omit colors outside of the
  /// typically defined range of the source of the colors (such as the
  /// bounds of an image or the defining geometry of a gradient).
  enum class TileMode {
    /// Replicate the edge color if the shader draws outside of its original
    /// bounds.
    kClamp,

    /// Repeat the shader's image horizontally and vertically (or both along and
    /// perpendicular to a gradient's geometry).
    kRepeat,

    /// Repeat the shader's image horizontally and vertically, seamlessly
    /// alternating mirrored images.
    kMirror,

    /// Render the shader's image pixels only within its original bounds. If the
    /// shader draws outside of its original bounds, transparent black is drawn
    /// instead.
    kDecal,
  };

  enum class ClipOperation {
    kDifference,
    kIntersect,
  };

  Entity();

  ~Entity();

  const Matrix& GetTransformation() const;

  void SetTransformation(const Matrix& transformation);

  std::optional<Rect> GetCoverage() const;

  Contents::StencilCoverage GetStencilCoverage(
      const std::optional<Rect>& current_stencil_coverage) const;

  bool ShouldRender(const std::optional<Rect>& stencil_coverage) const;

  void SetContents(std::shared_ptr<Contents> contents);

  const std::shared_ptr<Contents>& GetContents() const;

  void SetStencilDepth(uint32_t stencil_depth);

  void IncrementStencilDepth(uint32_t increment);

  uint32_t GetStencilDepth() const;

  void SetBlendMode(BlendMode blend_mode);

  BlendMode GetBlendMode() const;

  bool Render(const ContentContext& renderer, RenderPass& parent_pass) const;

  static bool BlendModeShouldCoverWholeScreen(BlendMode blend_mode);

 private:
  Matrix transformation_;
  std::shared_ptr<Contents> contents_;
  BlendMode blend_mode_ = BlendMode::kSourceOver;
  uint32_t stencil_depth_ = 0u;
};

}  // namespace impeller