paint.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_DISPLAY_LIST_PAINT_H_
#define FLUTTER_IMPELLER_DISPLAY_LIST_PAINT_H_
 
#include <memory>
 
#include "display_list/effects/dl_color_filter.h"
#include "display_list/effects/dl_color_sources.h"
#include "display_list/effects/dl_image_filter.h"
#include "impeller/display_list/color_filter.h"
#include "impeller/display_list/image_filter.h"
#include "impeller/entity/contents/color_source_contents.h"
#include "impeller/entity/contents/content_context.h"
#include "impeller/entity/contents/contents.h"
#include "impeller/entity/contents/filters/color_filter_contents.h"
#include "impeller/entity/contents/filters/filter_contents.h"
#include "impeller/entity/contents/texture_contents.h"
#include "impeller/entity/entity.h"
#include "impeller/entity/geometry/geometry.h"
#include "impeller/geometry/color.h"
#include "impeller/geometry/stroke_parameters.h"
#include "impeller/renderer/context.h"
 
namespace impeller {
 
struct Paint {
  using ImageFilterProc = std::function<std::shared_ptr<FilterContents>(
      FilterInput::Ref,
      const Matrix& effect_transform,
      Entity::RenderingMode rendering_mode)>;
  using MaskFilterProc = std::function<std::shared_ptr<FilterContents>(
      FilterInput::Ref,
      bool is_solid_color,
      const Matrix& effect_transform)>;
  using ColorSourceProc = std::function<std::shared_ptr<ColorSourceContents>()>;
 
  /// @brief Whether or not a save layer with the provided paint can perform the
  ///        opacity peephole optimization.
  static bool CanApplyOpacityPeephole(const Paint& paint) {
    return paint.blend_mode == BlendMode::kSrcOver &&
           paint.invert_colors == false &&
           !paint.mask_blur_descriptor.has_value() &&
           paint.image_filter == nullptr && paint.color_filter == nullptr;
  }
 
  enum class Style {
    kFill,
    kStroke,
  };
 
  struct MaskBlurDescriptor {
    FilterContents::BlurStyle style;
    Sigma sigma;
    /// Text mask blurs need to not apply the CTM to the blur kernel.
    /// See: https://github.com/flutter/flutter/issues/115112
    bool respect_ctm = true;
 
    std::shared_ptr<FilterContents> CreateMaskBlur(
        std::shared_ptr<TextureContents> texture_contents,
        FillRectGeometry* rect_geom) const;
 
    std::shared_ptr<FilterContents> CreateMaskBlur(
        const FilterInput::Ref& input,
        bool is_solid_color,
        const Matrix& ctm) const;
 
    std::shared_ptr<Contents> CreateMaskBlur(
        const Paint& paint,
        const ContentContext& renderer,
        const Geometry* geometry,
        std::shared_ptr<ColorSourceContents> contents,
        bool needs_color_filter,
        FillRectGeometry* out_geom) const;
  };
 
  Color color = Color::Black();
  const flutter::DlColorSource* color_source = nullptr;
  const flutter::DlColorFilter* color_filter = nullptr;
  const flutter::DlImageFilter* image_filter = nullptr;
 
  StrokeParameters stroke;
  Style style = Style::kFill;
  BlendMode blend_mode = BlendMode::kSrcOver;
  bool invert_colors = false;
  bool anti_alias = true;
 
  std::optional<MaskBlurDescriptor> mask_blur_descriptor;
 
  /// @brief   Return an optional StrokeParameters if this Paint is a stroked
  ///          Paint, otherwise return a nullopt.
  /// @return  An optional set of StrokeParameters
  std::optional<StrokeParameters> GetStroke() const {
    return (style == Style::kStroke) ? std::optional(stroke) : std::nullopt;
  }
 
  /// @brief      Wrap this paint's configured filters to the given contents.
  /// @param[in]  input           The contents to wrap with paint's filters.
  /// @return     The filter-wrapped contents. If there are no filters that need
  ///             to be wrapped for the current paint configuration, the
  ///             original contents is returned.
  std::shared_ptr<Contents> WithFilters(const ContentContext& renderer,
                                        std::shared_ptr<Contents> input) const;
 
  /// @brief      Wrap this paint's configured filters to the given contents of
  ///             subpass target.
  /// @param[in]  input  The contents of subpass target to wrap with paint's
  ///                    filters.
  ///
  /// @return     The filter-wrapped contents. If there are no filters that need
  ///             to be wrapped for the current paint configuration, the
  ///             original contents is returned.
  std::shared_ptr<Contents> WithFiltersForSubpassTarget(
      const ContentContext& renderer,
      std::shared_ptr<Contents> input,
      const Matrix& effect_transform = Matrix()) const;
 
  /// @brief   Whether this paint has a color filter that can apply opacity
  bool HasColorFilter() const;
 
  /// @brief      Create a `ColorSourceContents` representing this paint's
  ///             shader/colors.
  /// @param[in]  renderer            The content context renderer.
  /// @param[in]  geometry            The geometry the color source is drawn
  ///                                 onto.
  /// @param[in]  geometry_transform  An optional transform representing a
  ///                                 layout/positioning transform applied to
  ///                                 the geometry. If provided, this is used to
  ///                                 adjust the color source's effect transform
  ///                                 to align it with the geometry's coordinate
  ///                                 space.
  /// @return     The generated color source contents.
  std::shared_ptr<ColorSourceContents> CreateContents(
      const ContentContext& renderer,
      const Geometry* geometry,
      const std::optional<Matrix>& geometry_transform = std::nullopt) const;
 
  std::shared_ptr<Contents> WithMaskBlur(std::shared_ptr<Contents> input,
                                         bool is_solid_color,
                                         const Matrix& ctm) const;
 
  std::shared_ptr<FilterContents> WithImageFilter(
      const ContentContext& renderer,
      const FilterInput::Variant& input,
      const Matrix& effect_transform,
      Entity::RenderingMode rendering_mode) const;
 
  /// @brief Convert display list colors + stops into impeller colors and
  ///        stops, taking care to ensure that the stops monotonically
  ///        increase from 0.0 to 1.0.
  ///
  /// The general process is:
  /// * Ensure that the first gradient stop value is 0.0. If not, insert a
  ///   new stop with a value of 0.0 and use the first gradient color as this
  ///   new stops color.
  /// * Ensure the last gradient stop value is 1.0. If not, insert a new stop
  ///   with a value of 1.0 and use the last gradient color as this stops color.
  /// * Clamp all gradient values between the values of 0.0 and 1.0.
  /// * For all stop values, ensure that the values are monotonically
  ///   increasing by clamping each value to a minimum of the previous stop
  ///   value and itself. For example, with stop values of 0.0, 0.5, 0.4, 1.0,
  ///   we would clamp such that the values were 0.0, 0.5, 0.5, 1.0.
  static void ConvertStops(const flutter::DlGradientColorSourceBase* gradient,
                           std::vector<Color>& colors,
                           std::vector<float>& stops);
 
 private:
  std::shared_ptr<Contents> WithColorFilter(
      std::shared_ptr<Contents> input,
      ColorFilterContents::AbsorbOpacity absorb_opacity =
          ColorFilterContents::AbsorbOpacity::kNo) const;
};
 
}  // namespace impeller
 
#endif  // FLUTTER_IMPELLER_DISPLAY_LIST_PAINT_H_