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/*
* Copyright 2011 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#ifndef GrPathUtils_DEFINED
#define GrPathUtils_DEFINED
#include "GrMatrix.h"
#include "SkPath.h"
#include "SkTArray.h"
/**
* Utilities for evaluating paths.
*/
namespace GrPathUtils {
SkScalar scaleToleranceToSrc(SkScalar devTol,
const GrMatrix& viewM,
const GrRect& pathBounds);
/// Since we divide by tol if we're computing exact worst-case bounds,
/// very small tolerances will be increased to gMinCurveTol.
int worstCasePointCount(const SkPath&,
int* subpaths,
SkScalar tol);
/// Since we divide by tol if we're computing exact worst-case bounds,
/// very small tolerances will be increased to gMinCurveTol.
uint32_t quadraticPointCount(const GrPoint points[], SkScalar tol);
uint32_t generateQuadraticPoints(const GrPoint& p0,
const GrPoint& p1,
const GrPoint& p2,
SkScalar tolSqd,
GrPoint** points,
uint32_t pointsLeft);
/// Since we divide by tol if we're computing exact worst-case bounds,
/// very small tolerances will be increased to gMinCurveTol.
uint32_t cubicPointCount(const GrPoint points[], SkScalar tol);
uint32_t generateCubicPoints(const GrPoint& p0,
const GrPoint& p1,
const GrPoint& p2,
const GrPoint& p3,
SkScalar tolSqd,
GrPoint** points,
uint32_t pointsLeft);
// A 2x3 matrix that goes from the 2d space coordinates to UV space where
// u^2-v = 0 specifies the quad. The matrix is determined by the control
// points of the quadratic.
class QuadUVMatrix {
public:
QuadUVMatrix() {};
// Initialize the matrix from the control pts
QuadUVMatrix(const GrPoint controlPts[3]) { this->set(controlPts); }
void set(const GrPoint controlPts[3]);
/**
* Applies the matrix to vertex positions to compute UV coords. This
* has been templated so that the compiler can easliy unroll the loop
* and reorder to avoid stalling for loads. The assumption is that a
* path renderer will have a small fixed number of vertices that it
* uploads for each quad.
*
* N is the number of vertices.
* STRIDE is the size of each vertex.
* UV_OFFSET is the offset of the UV values within each vertex.
* vertices is a pointer to the first vertex.
*/
template <int N, size_t STRIDE, size_t UV_OFFSET>
void apply(const void* vertices) {
intptr_t xyPtr = reinterpret_cast<intptr_t>(vertices);
intptr_t uvPtr = reinterpret_cast<intptr_t>(vertices) + UV_OFFSET;
float sx = fM[0];
float kx = fM[1];
float tx = fM[2];
float ky = fM[3];
float sy = fM[4];
float ty = fM[5];
for (int i = 0; i < N; ++i) {
const GrPoint* xy = reinterpret_cast<const GrPoint*>(xyPtr);
GrPoint* uv = reinterpret_cast<GrPoint*>(uvPtr);
uv->fX = sx * xy->fX + kx * xy->fY + tx;
uv->fY = ky * xy->fX + sy * xy->fY + ty;
xyPtr += STRIDE;
uvPtr += STRIDE;
}
}
private:
float fM[6];
};
// Converts a cubic into a sequence of quads. If working in device space
// use tolScale = 1, otherwise set based on stretchiness of the matrix. The
// result is sets of 3 points in quads (TODO: share endpoints in returned
// array)
// When we approximate a cubic {a,b,c,d} with a quadratic we may have to
// ensure that the new control point lies between the lines ab and cd. The
// convex path renderer requires this. It starts with a path where all the
// control points taken together form a convex polygon. It relies on this
// property and the quadratic approximation of cubics step cannot alter it.
// Setting constrainWithinTangents to true enforces this property. When this
// is true the cubic must be simple and dir must specify the orientation of
// the cubic. Otherwise, dir is ignored.
void convertCubicToQuads(const GrPoint p[4],
SkScalar tolScale,
bool constrainWithinTangents,
SkPath::Direction dir,
SkTArray<SkPoint, true>* quads);
};
#endif
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