tessellator_libtess.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_TESSELLATOR_TESSELLATOR_LIBTESS_H_
#define FLUTTER_IMPELLER_TESSELLATOR_TESSELLATOR_LIBTESS_H_
 
#include <functional>
#include <memory>
 
#include "flutter/impeller/geometry/path_source.h"
 
struct TESStesselator;
 
namespace impeller {
 
void DestroyTessellator(TESStesselator* tessellator);
 
using CTessellator =
    std::unique_ptr<TESStesselator, decltype(&DestroyTessellator)>;
 
//------------------------------------------------------------------------------
/// @brief      An extended tessellator that offers arbitrary/concave
///             tessellation via the libtess2 library.
///
///             This object is not thread safe, and its methods must not be
///             called from multiple threads.
///
class TessellatorLibtess {
 public:
  TessellatorLibtess();
 
  ~TessellatorLibtess();
 
  enum class Result {
    kSuccess,
    kInputError,
    kTessellationError,
  };
 
  /// @brief A callback that returns the results of the tessellation.
  ///
  ///        The index buffer may not be populated, in which case [indices] will
  ///        be nullptr and indices_count will be 0.
  using BuilderCallback = std::function<bool(const float* vertices,
                                             size_t vertices_count,
                                             const uint16_t* indices,
                                             size_t indices_count)>;
 
  //----------------------------------------------------------------------------
  /// @brief      Generates filled triangles from the path. A callback is
  ///             invoked once for the entire tessellation.
  ///
  /// @param[in]  source  The path source to tessellate.
  /// @param[in]  tolerance  The tolerance value for conversion of the path to
  ///                        a polyline. This value is often derived from the
  ///                        Matrix::GetMaxBasisLength of the CTM applied to the
  ///                        path for rendering.
  /// @param[in]  callback  The callback, return false to indicate failure.
  ///
  /// @return The result status of the tessellation.
  ///
  TessellatorLibtess::Result Tessellate(const PathSource& source,
                                        Scalar tolerance,
                                        const BuilderCallback& callback);
 
 private:
  CTessellator c_tessellator_;
 
  TessellatorLibtess(const TessellatorLibtess&) = delete;
 
  TessellatorLibtess& operator=(const TessellatorLibtess&) = delete;
};
 
}  // namespace impeller
 
#endif  // FLUTTER_IMPELLER_TESSELLATOR_TESSELLATOR_LIBTESS_H_