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/*
* Copyright 2017 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#ifndef GrGrCCGeometry_DEFINED
#define GrGrCCGeometry_DEFINED
#include "SkGeometry.h"
#include "SkNx.h"
#include "SkPoint.h"
#include "SkTArray.h"
/**
* This class chops device-space contours up into a series of segments that CCPR knows how to
* render. (See GrCCGeometry::Verb.)
*
* NOTE: This must be done in device space, since an affine transformation can change whether a
* curve is monotonic.
*/
class GrCCGeometry {
public:
// These are the verbs that CCPR knows how to draw. If a path has any segments that don't map to
// this list, then they are chopped into smaller ones that do. A list of these comprise a
// compact representation of what can later be expanded into GPU instance data.
enum class Verb : uint8_t {
kBeginPath, // Included only for caller convenience.
kBeginContour,
kLineTo,
kMonotonicQuadraticTo, // Monotonic relative to the vector between its endpoints [P2 - P0].
kMonotonicCubicTo,
kEndClosedContour, // endPt == startPt.
kEndOpenContour // endPt != startPt.
};
// These tallies track numbers of CCPR primitives that are required to draw a contour.
struct PrimitiveTallies {
int fTriangles; // Number of triangles in the contour's fan.
int fWoundTriangles; // Triangles (from the tessellator) whose winding magnitude > 1.
int fQuadratics;
int fCubics;
void operator+=(const PrimitiveTallies&);
PrimitiveTallies operator-(const PrimitiveTallies&) const;
bool operator==(const PrimitiveTallies&);
};
GrCCGeometry(int numSkPoints = 0, int numSkVerbs = 0)
: fPoints(numSkPoints * 3) // Reserve for a 3x expansion in points and verbs.
, fVerbs(numSkVerbs * 3) {}
const SkTArray<SkPoint, true>& points() const { SkASSERT(!fBuildingContour); return fPoints; }
const SkTArray<Verb, true>& verbs() const { SkASSERT(!fBuildingContour); return fVerbs; }
void reset() {
SkASSERT(!fBuildingContour);
fPoints.reset();
fVerbs.reset();
}
// This is included in case the caller needs to discard previously added contours. It is up to
// the caller to track counts and ensure we don't pop back into the middle of a different
// contour.
void resize_back(int numPoints, int numVerbs) {
SkASSERT(!fBuildingContour);
fPoints.resize_back(numPoints);
fVerbs.resize_back(numVerbs);
SkASSERT(fVerbs.empty() || fVerbs.back() == Verb::kEndOpenContour ||
fVerbs.back() == Verb::kEndClosedContour);
}
void beginPath();
void beginContour(const SkPoint& devPt);
void lineTo(const SkPoint& devPt);
void quadraticTo(const SkPoint& devP1, const SkPoint& devP2);
// We pass through inflection points and loop intersections using a line and quadratic(s)
// respectively. 'inflectPad' and 'loopIntersectPad' specify how close (in pixels) cubic
// segments are allowed to get to these points. For normal rendering you will want to use the
// default values, but these can be overridden for testing purposes.
//
// NOTE: loops do appear to require two full pixels of padding around the intersection point.
// With just one pixel-width of pad, we start to see bad pixels. Ultimately this has a
// minimal effect on the total amount of segments produced. Most sections that pass
// through the loop intersection can be approximated with a single quadratic anyway,
// regardless of whether we are use one pixel of pad or two (1.622 avg. quads per loop
// intersection vs. 1.489 on the tiger).
void cubicTo(const SkPoint& devP1, const SkPoint& devP2, const SkPoint& devP3,
float inflectPad = 0.55f, float loopIntersectPad = 2);
PrimitiveTallies endContour(); // Returns the numbers of primitives needed to draw the contour.
private:
inline void appendMonotonicQuadratics(const Sk2f& p0, const Sk2f& p1, const Sk2f& p2);
inline void appendSingleMonotonicQuadratic(const Sk2f& p0, const Sk2f& p1, const Sk2f& p2);
using AppendCubicFn = void(GrCCGeometry::*)(const Sk2f& p0, const Sk2f& p1,
const Sk2f& p2, const Sk2f& p3,
int maxSubdivisions);
static constexpr int kMaxSubdivionsPerCubicSection = 2;
template<AppendCubicFn AppendLeftRight>
inline void chopCubicAtMidTangent(const Sk2f& p0, const Sk2f& p1, const Sk2f& p2,
const Sk2f& p3, const Sk2f& tan0, const Sk2f& tan3,
int maxFutureSubdivisions = kMaxSubdivionsPerCubicSection);
template<AppendCubicFn AppendLeft, AppendCubicFn AppendRight>
inline void chopCubic(const Sk2f& p0, const Sk2f& p1, const Sk2f& p2, const Sk2f& p3,
float T, int maxFutureSubdivisions = kMaxSubdivionsPerCubicSection);
void appendMonotonicCubics(const Sk2f& p0, const Sk2f& p1, const Sk2f& p2, const Sk2f& p3,
int maxSubdivisions = kMaxSubdivionsPerCubicSection);
void appendCubicApproximation(const Sk2f& p0, const Sk2f& p1, const Sk2f& p2, const Sk2f& p3,
int maxSubdivisions = kMaxSubdivionsPerCubicSection);
// Transient state used while building a contour.
SkPoint fCurrAnchorPoint;
SkPoint fCurrFanPoint;
PrimitiveTallies fCurrContourTallies;
SkCubicType fCurrCubicType;
SkDEBUGCODE(bool fBuildingContour = false);
// TODO: These points could eventually be written directly to block-allocated GPU buffers.
SkSTArray<128, SkPoint, true> fPoints;
SkSTArray<128, Verb, true> fVerbs;
};
inline void GrCCGeometry::PrimitiveTallies::operator+=(const PrimitiveTallies& b) {
fTriangles += b.fTriangles;
fWoundTriangles += b.fWoundTriangles;
fQuadratics += b.fQuadratics;
fCubics += b.fCubics;
}
GrCCGeometry::PrimitiveTallies
inline GrCCGeometry::PrimitiveTallies::operator-(const PrimitiveTallies& b) const {
return {fTriangles - b.fTriangles,
fWoundTriangles - b.fWoundTriangles,
fQuadratics - b.fQuadratics,
fCubics - b.fCubics};
}
inline bool GrCCGeometry::PrimitiveTallies::operator==(const PrimitiveTallies& b) {
return fTriangles == b.fTriangles && fWoundTriangles == b.fWoundTriangles &&
fQuadratics == b.fQuadratics && fCubics == b.fCubics;
}
#endif
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