canvas.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.
 
#ifndef FLUTTER_IMPELLER_AIKS_CANVAS_H_
#define FLUTTER_IMPELLER_AIKS_CANVAS_H_
 
#include <deque>
#include <functional>
#include <memory>
#include <optional>
#include <vector>
 
#include "impeller/aiks/image.h"
#include "impeller/aiks/image_filter.h"
#include "impeller/aiks/paint.h"
#include "impeller/aiks/picture.h"
#include "impeller/core/sampler_descriptor.h"
#include "impeller/entity/entity.h"
#include "impeller/entity/entity_pass.h"
#include "impeller/entity/geometry/geometry.h"
#include "impeller/entity/geometry/vertices_geometry.h"
#include "impeller/geometry/matrix.h"
#include "impeller/geometry/path.h"
#include "impeller/geometry/point.h"
#include "impeller/geometry/vector.h"
#include "impeller/typographer/text_frame.h"
 
namespace impeller {
 
struct CanvasStackEntry {
  Matrix transform;
  // |cull_rect| is conservative screen-space bounds of the clipped output area
  std::optional<Rect> cull_rect;
  uint32_t clip_depth = 0u;
  size_t clip_height = 0u;
  // The number of clips tracked for this canvas stack entry.
  size_t num_clips = 0u;
  Entity::RenderingMode rendering_mode = Entity::RenderingMode::kDirect;
};
 
enum class PointStyle {
  /// @brief Points are drawn as squares.
  kRound,
 
  /// @brief Points are drawn as circles.
  kSquare,
};
 
/// Controls the behavior of the source rectangle given to DrawImageRect.
enum class SourceRectConstraint {
  /// @brief Faster, but may sample outside the bounds of the source rectangle.
  kFast,
 
  /// @brief Sample only within the source rectangle. May be slower.
  kStrict,
};
 
class Canvas {
 public:
  static constexpr uint32_t kMaxDepth = 1 << 24;
 
  struct DebugOptions {
    /// When enabled, layers that are rendered to an offscreen texture
    /// internally get a translucent checkerboard pattern painted over them.
    ///
    /// Requires the `IMPELLER_DEBUG` preprocessor flag.
    bool offscreen_texture_checkerboard = false;
  } debug_options;
 
  Canvas();
 
  explicit Canvas(Rect cull_rect);
 
  explicit Canvas(IRect cull_rect);
 
  virtual ~Canvas();
 
  virtual void Save(uint32_t total_content_depth = kMaxDepth);
 
  virtual void SaveLayer(
      const Paint& paint,
      std::optional<Rect> bounds = std::nullopt,
      const std::shared_ptr<ImageFilter>& backdrop_filter = nullptr,
      ContentBoundsPromise bounds_promise = ContentBoundsPromise::kUnknown,
      uint32_t total_content_depth = kMaxDepth);
 
  virtual bool Restore();
 
  size_t GetSaveCount() const;
 
  void RestoreToCount(size_t count);
 
  const Matrix& GetCurrentTransform() const;
 
  const std::optional<Rect> GetCurrentLocalCullingBounds() const;
 
  void ResetTransform();
 
  void Transform(const Matrix& transform);
 
  void Concat(const Matrix& transform);
 
  void PreConcat(const Matrix& transform);
 
  void Translate(const Vector3& offset);
 
  void Scale(const Vector2& scale);
 
  void Scale(const Vector3& scale);
 
  void Skew(Scalar sx, Scalar sy);
 
  void Rotate(Radians radians);
 
  void DrawPath(const Path& path, const Paint& paint);
 
  void DrawPaint(const Paint& paint);
 
  void DrawLine(const Point& p0, const Point& p1, const Paint& paint);
 
  void DrawRect(const Rect& rect, const Paint& paint);
 
  void DrawOval(const Rect& rect, const Paint& paint);
 
  void DrawRRect(const Rect& rect,
                 const Size& corner_radii,
                 const Paint& paint);
 
  void DrawCircle(const Point& center, Scalar radius, const Paint& paint);
 
  void DrawPoints(std::vector<Point> points,
                  Scalar radius,
                  const Paint& paint,
                  PointStyle point_style);
 
  void DrawImage(const std::shared_ptr<Image>& image,
                 Point offset,
                 const Paint& paint,
                 SamplerDescriptor sampler = {});
 
  void DrawImageRect(
      const std::shared_ptr<Image>& image,
      Rect source,
      Rect dest,
      const Paint& paint,
      SamplerDescriptor sampler = {},
      SourceRectConstraint src_rect_constraint = SourceRectConstraint::kFast);
 
  void ClipPath(
      const Path& path,
      Entity::ClipOperation clip_op = Entity::ClipOperation::kIntersect);
 
  void ClipRect(
      const Rect& rect,
      Entity::ClipOperation clip_op = Entity::ClipOperation::kIntersect);
 
  void ClipOval(
      const Rect& bounds,
      Entity::ClipOperation clip_op = Entity::ClipOperation::kIntersect);
 
  void ClipRRect(
      const Rect& rect,
      const Size& corner_radii,
      Entity::ClipOperation clip_op = Entity::ClipOperation::kIntersect);
 
  virtual void DrawTextFrame(const std::shared_ptr<TextFrame>& text_frame,
                             Point position,
                             const Paint& paint);
 
  void DrawVertices(const std::shared_ptr<VerticesGeometry>& vertices,
                    BlendMode blend_mode,
                    const Paint& paint);
 
  void DrawAtlas(const std::shared_ptr<Image>& atlas,
                 std::vector<Matrix> transforms,
                 std::vector<Rect> texture_coordinates,
                 std::vector<Color> colors,
                 BlendMode blend_mode,
                 SamplerDescriptor sampler,
                 std::optional<Rect> cull_rect,
                 const Paint& paint);
 
  Picture EndRecordingAsPicture();
 
 protected:
  std::deque<CanvasStackEntry> transform_stack_;
  std::optional<Rect> initial_cull_rect_;
  uint64_t current_depth_ = 0u;
 
  size_t GetClipHeight() const;
 
  void Initialize(std::optional<Rect> cull_rect);
 
  void Reset();
 
 private:
  std::unique_ptr<EntityPass> base_pass_;
  EntityPass* current_pass_ = nullptr;
 
  EntityPass& GetCurrentPass();
 
  virtual void AddRenderEntityToCurrentPass(Entity entity,
                                            bool reuse_depth = false);
  virtual void AddClipEntityToCurrentPass(Entity entity);
 
  void ClipGeometry(const std::shared_ptr<Geometry>& geometry,
                    Entity::ClipOperation clip_op);
 
  void IntersectCulling(Rect clip_bounds);
  void SubtractCulling(Rect clip_bounds);
 
  virtual void Save(
      bool create_subpass,
      uint32_t total_content_depth,
      BlendMode = BlendMode::kSourceOver,
      const std::shared_ptr<ImageFilter>& backdrop_filter = nullptr);
 
  void RestoreClip();
 
  bool AttemptDrawBlurredRRect(const Rect& rect,
                               Size corner_radii,
                               const Paint& paint);
 
  Canvas(const Canvas&) = delete;
 
  Canvas& operator=(const Canvas&) = delete;
};
 
}  // namespace impeller
 
#endif  // FLUTTER_IMPELLER_AIKS_CANVAS_H_