chromium/third_party/skia/src/core/SkEdge.cpp

/*
 * Copyright 2006 The Android Open Source Project
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#include "src/core/SkEdge.h"

#include "include/private/base/SkDebug.h"
#include "include/private/base/SkTo.h"
#include "src/base/SkMathPriv.h"
#include "src/core/SkFDot6.h"

#include <algorithm>
#include <utility>

/*
    In setLine, setQuadratic, setCubic, the first thing we do is to convert
    the points into FDot6. This is modulated by the shift parameter, which
    will either be 0, or something like 2 for antialiasing.

    In the float case, we want to turn the float into .6 by saying pt * 64,
    or pt * 256 for antialiasing. This is implemented as 1 << (shift + 6).

    In the fixed case, we want to turn the fixed into .6 by saying pt >> 10,
    or pt >> 8 for antialiasing. This is implemented as pt >> (10 - shift).
*/

static inline SkFixed SkFDot6ToFixedDiv2(SkFDot6 value) { … }

/////////////////////////////////////////////////////////////////////////

#ifdef SK_DEBUG
void SkEdge::dump() const { … }
#endif

int SkEdge::setLine(const SkPoint& p0, const SkPoint& p1, const SkIRect* clip, int shift) { … }

// called from a curve subclass
int SkEdge::updateLine(SkFixed x0, SkFixed y0, SkFixed x1, SkFixed y1)
{ … }

void SkEdge::chopLineWithClip(const SkIRect& clip)
{ … }

///////////////////////////////////////////////////////////////////////////////

/*  We store 1<<shift in a (signed) byte, so its maximum value is 1<<6 == 64.
    Note that this limits the number of lines we use to approximate a curve.
    If we need to increase this, we need to store fCurveCount in something
    larger than int8_t.
*/
#define MAX_COEFF_SHIFT …

static inline SkFDot6 cheap_distance(SkFDot6 dx, SkFDot6 dy)
{ … }

static inline int diff_to_shift(SkFDot6 dx, SkFDot6 dy, int shiftAA = 2)
{ … }

bool SkQuadraticEdge::setQuadraticWithoutUpdate(const SkPoint pts[3], int shift) { … }

int SkQuadraticEdge::setQuadratic(const SkPoint pts[3], int shift) { … }

int SkQuadraticEdge::updateQuadratic()
{ … }

/////////////////////////////////////////////////////////////////////////

static inline int SkFDot6UpShift(SkFDot6 x, int upShift) { … }

/*  f(1/3) = (8a + 12b + 6c + d) / 27
    f(2/3) = (a + 6b + 12c + 8d) / 27

    f(1/3)-b = (8a - 15b + 6c + d) / 27
    f(2/3)-c = (a + 6b - 15c + 8d) / 27

    use 16/512 to approximate 1/27
*/
static SkFDot6 cubic_delta_from_line(SkFDot6 a, SkFDot6 b, SkFDot6 c, SkFDot6 d)
{ … }

bool SkCubicEdge::setCubicWithoutUpdate(const SkPoint pts[4], int shift, bool sortY) { … }

int SkCubicEdge::setCubic(const SkPoint pts[4], int shift) { … }

int SkCubicEdge::updateCubic()
{ … }