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skia2/gm/convex_all_line_paths.cpp
Cary Clark c9b7c720dd two pass convexity 
This separates the existing convexity logic into
two passes. The first pass detects concavity by
counting the changes in direction.
The second pass computes the cross product to
see that all angles bend in the same direction, and
computes the dot product to see if the angle
doubles back on itself.

The second pass treats axis-aligned vectors
separately, and computes the dot and cross products
by comparing point values; it does not use arithmetic
to determine convexity, so it works with all finite
values.

A compile time switch enables returning concave
for co-linear diagonal points:
If successive points are not axis-aligned, and
those points are co-linear along a diagonal;
the path is treated as concave. This is conservative
but avoids paths that change convexity when the
are translated or scaled, since transforming the
path may cause the midpoint to shift to either
side of a line formed by the endpoints.

The compile time switch is set so that co-linear
diagonal points do not affect convexity. Note that
this permits shapes formerly considered concave, such
as stroked lines with round caps, to become convex;
this accounts for many of the GM differences.

A path may double back on itself and be convex;
for instance, a path containing a single line.

Path may have multiple initial moveTo verbs, or
trailing moveTo verbs, and still evaluate as convex.

A separate entry point, SkPathPriv::IsConvex()
allows passing an array of points instead of a path.

A legacy define has been checked into Chrome to
use the old code until layout tests have been
rebaselined.

R=reed@google.com,bsalomon@google.com
Bug:899689
Change-Id: I392bbe04836ffb19666ad92ab2a2404c56543019
Reviewed-on: https://skia-review.googlesource.com/c/173427
Reviewed-by: Mike Reed <reed@google.com>
Reviewed-by: Cary Clark <caryclark@google.com>
Commit-Queue: Cary Clark <caryclark@skia.org>
2018-12-13 13:04:44 +00:00

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/*
* Copyright 2015 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#include "gm.h"
#include "SkPolyUtils.h"
#include "SkPathPriv.h"
static void create_ngon(int n, SkPoint* pts, SkScalar width, SkScalar height) {
float angleStep = 360.0f / n, angle = 0.0f, sin, cos;
if ((n % 2) == 1) {
angle = angleStep/2.0f;
}
for (int i = 0; i < n; ++i) {
sin = SkScalarSinCos(SkDegreesToRadians(angle), &cos);
pts[i].fX = -sin * width;
pts[i].fY = cos * height;
angle += angleStep;
}
}
namespace ConvexLineOnlyData {
// narrow rect
const SkPoint gPoints0[] = {
{ -1.5f, -50.0f },
{ 1.5f, -50.0f },
{ 1.5f, 50.0f },
{ -1.5f, 50.0f }
};
// narrow rect on an angle
const SkPoint gPoints1[] = {
{ -50.0f, -49.0f },
{ -49.0f, -50.0f },
{ 50.0f, 49.0f },
{ 49.0f, 50.0f }
};
// trap - narrow on top - wide on bottom
const SkPoint gPoints2[] = {
{ -10.0f, -50.0f },
{ 10.0f, -50.0f },
{ 50.0f, 50.0f },
{ -50.0f, 50.0f }
};
// wide skewed rect
const SkPoint gPoints3[] = {
{ -50.0f, -50.0f },
{ 0.0f, -50.0f },
{ 50.0f, 50.0f },
{ 0.0f, 50.0f }
};
// thin rect with colinear-ish lines
const SkPoint gPoints4[] = {
{ -6.0f, -50.0f },
{ 4.0f, -50.0f },
#if SK_TREAT_COLINEAR_DIAGONAL_POINTS_AS_CONCAVE == 0
{ 5.0f, -25.0f }, // remove if collinear diagonal points are not concave
#endif
{ 6.0f, 0.0f },
#if SK_TREAT_COLINEAR_DIAGONAL_POINTS_AS_CONCAVE == 0
{ 5.0f, 25.0f }, // remove if collinear diagonal points are not concave
#endif
{ 4.0f, 50.0f },
{ -4.0f, 50.0f }
};
// degenerate
const SkPoint gPoints5[] = {
{ -0.025f, -0.025f },
{ 0.025f, -0.025f },
{ 0.025f, 0.025f },
{ -0.025f, 0.025f }
};
// Triangle in which the first point should fuse with last
const SkPoint gPoints6[] = {
{ -20.0f, -13.0f },
{ -20.0f, -13.05f },
{ 20.0f, -13.0f },
{ 20.0f, 27.0f }
};
// thin rect with colinear lines
const SkPoint gPoints7[] = {
{ -10.0f, -50.0f },
{ 10.0f, -50.0f },
{ 10.0f, -25.0f },
{ 10.0f, 0.0f },
{ 10.0f, 25.0f },
{ 10.0f, 50.0f },
{ -10.0f, 50.0f }
};
// capped teardrop
const SkPoint gPoints8[] = {
{ 50.00f, 50.00f },
{ 0.00f, 50.00f },
{ -15.45f, 47.55f },
{ -29.39f, 40.45f },
{ -40.45f, 29.39f },
{ -47.55f, 15.45f },
{ -50.00f, 0.00f },
{ -47.55f, -15.45f },
{ -40.45f, -29.39f },
{ -29.39f, -40.45f },
{ -15.45f, -47.55f },
{ 0.00f, -50.00f },
{ 50.00f, -50.00f }
};
// teardrop
const SkPoint gPoints9[] = {
{ 4.39f, 40.45f },
{ -9.55f, 47.55f },
{ -25.00f, 50.00f },
{ -40.45f, 47.55f },
{ -54.39f, 40.45f },
{ -65.45f, 29.39f },
{ -72.55f, 15.45f },
{ -75.00f, 0.00f },
{ -72.55f, -15.45f },
{ -65.45f, -29.39f },
{ -54.39f, -40.45f },
{ -40.45f, -47.55f },
{ -25.0f, -50.0f },
{ -9.55f, -47.55f },
{ 4.39f, -40.45f },
{ 75.00f, 0.00f }
};
// clipped triangle
const SkPoint gPoints10[] = {
{ -10.0f, -50.0f },
{ 10.0f, -50.0f },
{ 50.0f, 31.0f },
{ 40.0f, 50.0f },
{ -40.0f, 50.0f },
{ -50.0f, 31.0f },
};
const SkPoint* gPoints[] = {
gPoints0, gPoints1, gPoints2, gPoints3, gPoints4, gPoints5, gPoints6,
gPoints7, gPoints8, gPoints9, gPoints10,
};
const size_t gSizes[] = {
SK_ARRAY_COUNT(gPoints0),
SK_ARRAY_COUNT(gPoints1),
SK_ARRAY_COUNT(gPoints2),
SK_ARRAY_COUNT(gPoints3),
SK_ARRAY_COUNT(gPoints4),
SK_ARRAY_COUNT(gPoints5),
SK_ARRAY_COUNT(gPoints6),
SK_ARRAY_COUNT(gPoints7),
SK_ARRAY_COUNT(gPoints8),
SK_ARRAY_COUNT(gPoints9),
SK_ARRAY_COUNT(gPoints10),
};
static_assert(SK_ARRAY_COUNT(gSizes) == SK_ARRAY_COUNT(gPoints), "array_mismatch");
}
namespace skiagm {
// This GM is intended to exercise Ganesh's handling of convex line-only
// paths
class ConvexLineOnlyPathsGM : public GM {
public:
ConvexLineOnlyPathsGM(bool doStrokeAndFill) : fDoStrokeAndFill(doStrokeAndFill) {
this->setBGColor(0xFFFFFFFF);
}
protected:
SkString onShortName() override {
if (fDoStrokeAndFill) {
return SkString("convex-lineonly-paths-stroke-and-fill");
}
return SkString("convex-lineonly-paths");
}
SkISize onISize() override { return SkISize::Make(kGMWidth, kGMHeight); }
bool runAsBench() const override { return true; }
static SkPath GetPath(int index, SkPath::Direction dir) {
std::unique_ptr<SkPoint[]> data(nullptr);
const SkPoint* points;
int numPts;
if (index < (int) SK_ARRAY_COUNT(ConvexLineOnlyData::gPoints)) {
// manually specified
points = ConvexLineOnlyData::gPoints[index];
numPts = (int)ConvexLineOnlyData::gSizes[index];
} else {
// procedurally generated
SkScalar width = kMaxPathHeight/2;
SkScalar height = kMaxPathHeight/2;
switch (index-SK_ARRAY_COUNT(ConvexLineOnlyData::gPoints)) {
case 0:
numPts = 3;
break;
case 1:
numPts = 4;
break;
case 2:
numPts = 5;
break;
case 3: // squashed pentagon
numPts = 5;
width = kMaxPathHeight/5;
break;
case 4:
numPts = 6;
break;
case 5:
numPts = 8;
break;
case 6: // squashed octogon
numPts = 8;
width = kMaxPathHeight/5;
break;
case 7:
numPts = 20;
break;
case 8:
numPts = 100;
break;
default:
numPts = 3;
break;
}
data.reset(new SkPoint[numPts]);
create_ngon(numPts, data.get(), width, height);
points = data.get();
}
SkPath path;
if (SkPath::kCW_Direction == dir) {
path.moveTo(points[0]);
for (int i = 1; i < numPts; ++i) {
path.lineTo(points[i]);
}
} else {
path.moveTo(points[numPts-1]);
for (int i = numPts-2; i >= 0; --i) {
path.lineTo(points[i]);
}
}
path.close();
#ifdef SK_DEBUG
// Each path this method returns should be convex, only composed of
// lines, wound the right direction, and short enough to fit in one
// of the GMs rows.
SkASSERT(path.isConvex());
SkASSERT(SkPath::kLine_SegmentMask == path.getSegmentMasks());
SkPathPriv::FirstDirection actualDir;
SkASSERT(SkPathPriv::CheapComputeFirstDirection(path, &actualDir));
SkASSERT(SkPathPriv::AsFirstDirection(dir) == actualDir);
SkRect bounds = path.getBounds();
SkASSERT(SkScalarNearlyEqual(bounds.centerX(), 0.0f));
SkASSERT(bounds.height() <= kMaxPathHeight);
#endif
return path;
}
// Draw a single path several times, shrinking it, flipping its direction
// and changing its start vertex each time.
void drawPath(SkCanvas* canvas, int index, SkPoint* offset) {
SkPoint center;
{
SkPath path = GetPath(index, SkPath::kCW_Direction);
if (offset->fX+path.getBounds().width() > kGMWidth) {
offset->fX = 0;
offset->fY += kMaxPathHeight;
if (fDoStrokeAndFill) {
offset->fX += kStrokeWidth / 2.0f;
offset->fY += kStrokeWidth / 2.0f;
}
}
center = { offset->fX + SkScalarHalf(path.getBounds().width()), offset->fY};
offset->fX += path.getBounds().width();
if (fDoStrokeAndFill) {
offset->fX += kStrokeWidth;
}
}
const SkColor colors[2] = { SK_ColorBLACK, SK_ColorWHITE };
const SkPath::Direction dirs[2] = { SkPath::kCW_Direction, SkPath::kCCW_Direction };
const float scales[] = { 1.0f, 0.75f, 0.5f, 0.25f, 0.1f, 0.01f, 0.001f };
const SkPaint::Join joins[3] = { SkPaint::kRound_Join,
SkPaint::kBevel_Join,
SkPaint::kMiter_Join };
SkPaint paint;
paint.setAntiAlias(true);
for (size_t i = 0; i < SK_ARRAY_COUNT(scales); ++i) {
SkPath path = GetPath(index, dirs[i%2]);
if (fDoStrokeAndFill) {
paint.setStyle(SkPaint::kStrokeAndFill_Style);
paint.setStrokeJoin(joins[i%3]);
paint.setStrokeWidth(SkIntToScalar(kStrokeWidth));
}
canvas->save();
canvas->translate(center.fX, center.fY);
canvas->scale(scales[i], scales[i]);
paint.setColor(colors[i%2]);
canvas->drawPath(path, paint);
canvas->restore();
}
}
void onDraw(SkCanvas* canvas) override {
// the right edge of the last drawn path
SkPoint offset = { 0, SkScalarHalf(kMaxPathHeight) };
if (fDoStrokeAndFill) {
offset.fX += kStrokeWidth / 2.0f;
offset.fY += kStrokeWidth / 2.0f;
}
for (int i = 0; i < kNumPaths; ++i) {
this->drawPath(canvas, i, &offset);
}
{
// Repro for crbug.com/472723 (Missing AA on portions of graphic with GPU rasterization)
SkPaint p;
p.setAntiAlias(true);
if (fDoStrokeAndFill) {
p.setStyle(SkPaint::kStrokeAndFill_Style);
p.setStrokeJoin(SkPaint::kMiter_Join);
p.setStrokeWidth(SkIntToScalar(kStrokeWidth));
}
SkPath p1;
p1.moveTo(60.8522949f, 364.671021f);
p1.lineTo(59.4380493f, 364.671021f);
p1.lineTo(385.414276f, 690.647217f);
p1.lineTo(386.121399f, 689.940125f);
canvas->save();
canvas->translate(356.0f, 50.0f);
canvas->drawPath(p1, p);
canvas->restore();
// Repro for crbug.com/869172 (SVG path incorrectly simplified when using GPU
// Rasterization). This will only draw anything in the stroke-and-fill version.
SkPath p2;
p2.moveTo(10.f, 0.f);
p2.lineTo(38.f, 0.f);
p2.lineTo(66.f, 0.f);
p2.lineTo(94.f, 0.f);
p2.lineTo(122.f, 0.f);
p2.lineTo(150.f, 0.f);
p2.lineTo(150.f, 0.f);
p2.lineTo(122.f, 0.f);
p2.lineTo(94.f, 0.f);
p2.lineTo(66.f, 0.f);
p2.lineTo(38.f, 0.f);
p2.lineTo(10.f, 0.f);
p2.close();
canvas->save();
canvas->translate(0.0f, 500.0f);
canvas->drawPath(p2, p);
canvas->restore();
// Repro for crbug.com/856137. This path previously caused GrAAConvexTessellator to turn
// inset rings into outsets when adjacent bisector angles converged outside the previous
// ring due to accumulated error.
SkPath p3;
p3.setFillType(SkPath::kEvenOdd_FillType);
p3.moveTo(1184.96f, 982.557f);
p3.lineTo(1183.71f, 982.865f);
p3.lineTo(1180.99f, 982.734f);
p3.lineTo(1178.5f, 981.541f);
p3.lineTo(1176.35f, 979.367f);
p3.lineTo(1178.94f, 938.854f);
p3.lineTo(1181.35f, 936.038f);
p3.lineTo(1183.96f, 934.117f);
p3.lineTo(1186.67f, 933.195f);
p3.lineTo(1189.36f, 933.342f);
p3.lineTo(1191.58f, 934.38f);
p3.close();
canvas->save();
SkMatrix m;
m.setAll(0.0893210843f, 0, 79.1197586f, 0, 0.0893210843f, 300, 0, 0, 1);
canvas->concat(m);
canvas->drawPath(p3, p);
canvas->restore();
}
}
private:
static constexpr int kStrokeWidth = 10;
static constexpr int kNumPaths = 20;
static constexpr int kMaxPathHeight = 100;
static constexpr int kGMWidth = 512;
static constexpr int kGMHeight = 512;
bool fDoStrokeAndFill;
typedef GM INHERITED;
};
//////////////////////////////////////////////////////////////////////////////
DEF_GM(return new ConvexLineOnlyPathsGM(false);)
DEF_GM(return new ConvexLineOnlyPathsGM(true);)
}
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