shadow.h

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#pragma once
 
#include "roo_display/core/rasterizable.h"
 
namespace roo_display {
 
/// Rasterizable drop shadow for rounded rectangles.
class RoundRectShadow : public Rasterizable {
 public:
  /// Shadow specification parameters.
  struct Spec {
    // Extents of the shadow.
    int16_t x, y, w, h;
 
    // External radius of the shadow at full extents.
    uint8_t radius;
 
    // 'Internal' shadow radius, within which the shadow is not diffused.
    // Generally the same as the corner radius of the widget casting the shadow.
    uint8_t border;
 
    // The alpha at a point where the shadow is not diffuset.
    uint8_t alpha_start;
 
    // 256 * how much the alpha decreases per each pixel of distance.
    uint16_t alpha_step;
  };
 
  /// Construct a rounded-rect shadow.
  ///
  /// `extents` refer to the original object area. `blur_radius` approximates
  /// elevation (shadow growth). `corner_radius` indicates rounded corners of
  /// the casting object.
  RoundRectShadow(roo_display::Box extents, Color color, uint8_t blur_radius,
                  uint8_t dx, uint8_t dy, uint8_t corner_radius);
 
  Box extents() const override { return shadow_extents_; }
 
  void readColors(const int16_t* x, const int16_t* y, uint32_t count,
                  Color* result) const override;
 
  bool readColorRect(int16_t xMin, int16_t yMin, int16_t xMax, int16_t yMax,
                     roo_display::Color* result) const override;
 
 private:
  Spec spec_;
  Box object_extents_;
  Box shadow_extents_;
  uint8_t corner_radius_;
  Color color_;
};
 
}  // namespace roo_display