chromium/third_party/skia/src/gpu/tessellate/Tessellation.cpp

/*
 * Copyright 2021 Google LLC.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */
#include "src/gpu/tessellate/Tessellation.h"

#include "include/core/SkPath.h"
#include "include/core/SkPathTypes.h"
#include "include/core/SkRect.h"
#include "include/private/base/SkFloatingPoint.h"
#include "include/private/base/SkTArray.h"
#include "src/base/SkUtils.h"
#include "src/base/SkVx.h"
#include "src/core/SkGeometry.h"
#include "src/core/SkPathPriv.h"
#include "src/gpu/tessellate/CullTest.h"
#include "src/gpu/tessellate/WangsFormula.h"

usingnamespaceskia_private;

namespace skgpu::tess {

namespace {

float2;
float4;

// This value only protects us against getting stuck in infinite recursion due to fp32 precision
// issues. Mathematically, every curve should reduce to manageable visible sections in O(log N)
// chops, where N is the the magnitude of its control points.
//
// But, to define a protective upper bound, a cubic can enter or exit the viewport as many as 6
// times. So we may need to refine the curve (via binary search chopping at T=.5) up to 6 times.
//
// Furthermore, chopping a cubic at T=.5 may only reduce its length by 1/8 (.5^3), so we may require
// up to 6 chops in order to reduce the length by 1/2.
constexpr static int kMaxChopsPerCurve = …/*max number of viewport boundary crosses*/;

// Writes a new path, chopping as necessary so no verbs require more segments than
// kMaxTessellationSegmentsPerCurve. Curves completely outside the viewport are flattened into
// lines.
class PathChopper { … };

}  // namespace

SkPath PreChopPathCurves(float tessellationPrecision,
                         const SkPath& path,
                         const SkMatrix& matrix,
                         const SkRect& viewport) { … }

int FindCubicConvex180Chops(const SkPoint pts[], float T[2], bool* areCusps) { … }

}  // namespace skgpu::tess