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/*
* Copyright 2019 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#include "samplecode/Sample.h"
#include "src/gpu/geometry/GrQuad.h"
#include "src/gpu/ops/GrQuadPerEdgeAA.h"
#include "include/core/SkCanvas.h"
#include "include/core/SkPaint.h"
#include "include/effects/SkDashPathEffect.h"
#include "include/pathops/SkPathOps.h"
// Draw a line through the two points, outset by a fixed length in screen space
static void draw_extended_line(SkCanvas* canvas, const SkPaint paint,
const SkPoint& p0, const SkPoint& p1) {
SkVector v = p1 - p0;
v.setLength(v.length() + 3.f);
canvas->drawLine(p1 - v, p0 + v, paint);
// Draw normal vector too
SkPaint normalPaint = paint;
normalPaint.setPathEffect(nullptr);
normalPaint.setStrokeWidth(paint.getStrokeWidth() / 4.f);
SkVector n = {v.fY, -v.fX};
n.setLength(.25f);
SkPoint m = (p0 + p1) * 0.5f;
canvas->drawLine(m, m + n, normalPaint);
}
static void make_aa_line(const SkPoint& p0, const SkPoint& p1, bool aaOn,
bool outset, SkPoint line[2]) {
SkVector n = {0.f, 0.f};
if (aaOn) {
SkVector v = p1 - p0;
n = outset ? SkVector::Make(v.fY, -v.fX) : SkVector::Make(-v.fY, v.fX);
n.setLength(0.5f);
}
line[0] = p0 + n;
line[1] = p1 + n;
}
// To the line through l0-l1, not capped at the end points of the segment
static SkScalar signed_distance(const SkPoint& p, const SkPoint& l0, const SkPoint& l1) {
SkVector v = l1 - l0;
v.normalize();
SkVector n = {v.fY, -v.fX};
SkScalar c = -n.dot(l0);
return n.dot(p) + c;
}
static SkScalar get_area_coverage(const bool edgeAA[4], const SkPoint corners[4],
const SkPoint& point) {
SkPath shape;
shape.addPoly(corners, 4, true);
SkPath pixel;
pixel.addRect(SkRect::MakeXYWH(point.fX - 0.5f, point.fY - 0.5f, 1.f, 1.f));
SkPath intersection;
if (!Op(shape, pixel, kIntersect_SkPathOp, &intersection) || intersection.isEmpty()) {
return 0.f;
}
// Calculate area of the convex polygon
SkScalar area = 0.f;
for (int i = 0; i < intersection.countPoints(); ++i) {
SkPoint p0 = intersection.getPoint(i);
SkPoint p1 = intersection.getPoint((i + 1) % intersection.countPoints());
SkScalar det = p0.fX * p1.fY - p1.fX * p0.fY;
area += det;
}
// Scale by 1/2, then take abs value (this area formula is signed based on point winding, but
// since it's convex, just make it positive).
area = SkScalarAbs(0.5f * area);
// Now account for the edge AA. If the pixel center is outside of a non-AA edge, turn of its
// coverage. If the pixel only intersects non-AA edges, then set coverage to 1.
bool needsNonAA = false;
SkScalar edgeD[4];
for (int i = 0; i < 4; ++i) {
SkPoint e0 = corners[i];
SkPoint e1 = corners[(i + 1) % 4];
edgeD[i] = -signed_distance(point, e0, e1);
if (!edgeAA[i]) {
if (edgeD[i] < -1e-4f) {
return 0.f; // Outside of non-AA line
}
needsNonAA = true;
}
}
// Otherwise inside the shape, so check if any AA edge exerts influence over nonAA
if (needsNonAA) {
for (int i = 0; i < 4; i++) {
if (edgeAA[i] && edgeD[i] < 0.5f) {
needsNonAA = false;
break;
}
}
}
return needsNonAA ? 1.f : area;
}
// FIXME take into account max coverage properly,
static SkScalar get_edge_dist_coverage(const bool edgeAA[4], const SkPoint corners[4],
const SkPoint outsetLines[8], const SkPoint insetLines[8],
const SkPoint& point) {
bool flip = false;
// If the quad has been inverted, the original corners will not all be on the negative side of
// every outset line. When that happens, calculate coverage using the "inset" lines and flip
// the signed distance
for (int i = 0; i < 4; ++i) {
for (int j = 0; j < 4; ++j) {
SkScalar d = signed_distance(corners[i], outsetLines[j * 2], outsetLines[j * 2 + 1]);
if (d > 1e-4f) {
flip = true;
break;
}
}
if (flip) {
break;
}
}
const SkPoint* lines = flip ? insetLines : outsetLines;
SkScalar minCoverage = 1.f;
for (int i = 0; i < 4; ++i) {
// Multiply by negative 1 so that outside points have negative distances
SkScalar d = (flip ? 1 : -1) * signed_distance(point, lines[i * 2], lines[i * 2 + 1]);
if (!edgeAA[i] && d >= -1e-4f) {
d = 1.f;
}
if (d < minCoverage) {
minCoverage = d;
if (minCoverage < 0.f) {
break; // Outside the shape
}
}
}
return minCoverage < 0.f ? 0.f : minCoverage;
}
static bool inside_triangle(const SkPoint& point, const SkPoint& t0, const SkPoint& t1,
const SkPoint& t2, SkScalar bary[3]) {
// Check sign of t0 to (t1,t2). If it is positive, that means the normals point into the
// triangle otherwise the normals point outside the triangle so update edge distances as
// necessary
bool flip = signed_distance(t0, t1, t2) < 0.f;
SkScalar d0 = (flip ? -1 : 1) * signed_distance(point, t0, t1);
SkScalar d1 = (flip ? -1 : 1) * signed_distance(point, t1, t2);
SkScalar d2 = (flip ? -1 : 1) * signed_distance(point, t2, t0);
// Be a little forgiving
if (d0 < -1e-4f || d1 < -1e-4f || d2 < -1e-4f) {
return false;
}
// Inside, so calculate barycentric coords from the sideline distances
SkScalar d01 = (t0 - t1).length();
SkScalar d12 = (t1 - t2).length();
SkScalar d20 = (t2 - t0).length();
if (SkScalarNearlyZero(d12) || SkScalarNearlyZero(d20) || SkScalarNearlyZero(d01)) {
// Empty degenerate triangle
return false;
}
// Coordinates for a vertex use distances to the opposite edge
bary[0] = d1 * d12;
bary[1] = d2 * d20;
bary[2] = d0 * d01;
// And normalize
SkScalar sum = bary[0] + bary[1] + bary[2];
bary[0] /= sum;
bary[1] /= sum;
bary[2] /= sum;
return true;
}
static SkScalar get_framed_coverage(const SkPoint outer[4], const SkScalar outerCoverages[4],
const SkPoint inner[4], const SkScalar innerCoverages[4],
const SkRect& geomDomain, const SkPoint& point) {
// Triangles are ordered clock wise. Indices >= 4 refer to inner[i - 4]. Otherwise its outer[i].
static const int kFrameTris[] = {
0, 1, 4, 4, 1, 5,
1, 2, 5, 5, 2, 6,
2, 3, 6, 6, 3, 7,
3, 0, 7, 7, 0, 4,
4, 5, 7, 7, 5, 6
};
static const int kNumTris = 10;
SkScalar bary[3];
for (int i = 0; i < kNumTris; ++i) {
int i0 = kFrameTris[i * 3];
int i1 = kFrameTris[i * 3 + 1];
int i2 = kFrameTris[i * 3 + 2];
SkPoint t0 = i0 >= 4 ? inner[i0 - 4] : outer[i0];
SkPoint t1 = i1 >= 4 ? inner[i1 - 4] : outer[i1];
SkPoint t2 = i2 >= 4 ? inner[i2 - 4] : outer[i2];
if (inside_triangle(point, t0, t1, t2, bary)) {
// Calculate coverage by barycentric interpolation of coverages
SkScalar c0 = i0 >= 4 ? innerCoverages[i0 - 4] : outerCoverages[i0];
SkScalar c1 = i1 >= 4 ? innerCoverages[i1 - 4] : outerCoverages[i1];
SkScalar c2 = i2 >= 4 ? innerCoverages[i2 - 4] : outerCoverages[i2];
SkScalar coverage = bary[0] * c0 + bary[1] * c1 + bary[2] * c2;
if (coverage < 0.5f) {
// Check distances to domain
SkScalar l = SkTPin(point.fX - geomDomain.fLeft, 0.f, 1.f);
SkScalar t = SkTPin(point.fY - geomDomain.fTop, 0.f, 1.f);
SkScalar r = SkTPin(geomDomain.fRight - point.fX, 0.f, 1.f);
SkScalar b = SkTPin(geomDomain.fBottom - point.fY, 0.f, 1.f);
coverage = std::min(coverage, l * t * r * b);
}
return coverage;
}
}
// Not inside any triangle
return 0.f;
}
static constexpr SkScalar kViewScale = 100.f;
static constexpr SkScalar kViewOffset = 200.f;
class DegenerateQuadSample : public Sample {
public:
DegenerateQuadSample(const SkRect& rect)
: fOuterRect(rect)
, fCoverageMode(CoverageMode::kArea) {
fOuterRect.toQuad(fCorners);
for (int i = 0; i < 4; ++i) {
fEdgeAA[i] = true;
}
}
void onDrawContent(SkCanvas* canvas) override {
static const SkScalar kDotParams[2] = {1.f / kViewScale, 12.f / kViewScale};
sk_sp<SkPathEffect> dots = SkDashPathEffect::Make(kDotParams, 2, 0.f);
static const SkScalar kDashParams[2] = {8.f / kViewScale, 12.f / kViewScale};
sk_sp<SkPathEffect> dashes = SkDashPathEffect::Make(kDashParams, 2, 0.f);
SkPaint circlePaint;
circlePaint.setAntiAlias(true);
SkPaint linePaint;
linePaint.setAntiAlias(true);
linePaint.setStyle(SkPaint::kStroke_Style);
linePaint.setStrokeWidth(4.f / kViewScale);
linePaint.setStrokeJoin(SkPaint::kRound_Join);
linePaint.setStrokeCap(SkPaint::kRound_Cap);
canvas->translate(kViewOffset, kViewOffset);
canvas->scale(kViewScale, kViewScale);
// Draw the outer rectangle as a dotted line
linePaint.setPathEffect(dots);
canvas->drawRect(fOuterRect, linePaint);
bool valid = this->isValid();
if (valid) {
SkPoint outsets[8];
SkPoint insets[8];
// Calculate inset and outset lines for edge-distance visualization
for (int i = 0; i < 4; ++i) {
make_aa_line(fCorners[i], fCorners[(i + 1) % 4], fEdgeAA[i], true, outsets + i * 2);
make_aa_line(fCorners[i], fCorners[(i + 1) % 4], fEdgeAA[i], false, insets + i * 2);
}
// Calculate inner and outer meshes for GPU visualization
SkPoint gpuOutset[4];
SkScalar gpuOutsetCoverage[4];
SkPoint gpuInset[4];
SkScalar gpuInsetCoverage[4];
SkRect gpuDomain;
this->getTessellatedPoints(gpuInset, gpuInsetCoverage, gpuOutset, gpuOutsetCoverage,
&gpuDomain);
// Visualize the coverage values across the clamping rectangle, but test pixels outside
// of the "outer" rect since some quad edges can be outset extra far.
SkPaint pixelPaint;
pixelPaint.setAntiAlias(true);
SkRect covRect = fOuterRect.makeOutset(2.f, 2.f);
for (SkScalar py = covRect.fTop; py < covRect.fBottom; py += 1.f) {
for (SkScalar px = covRect.fLeft; px < covRect.fRight; px += 1.f) {
// px and py are the top-left corner of the current pixel, so get center's
// coordinate
SkPoint pixelCenter = {px + 0.5f, py + 0.5f};
SkScalar coverage;
if (fCoverageMode == CoverageMode::kArea) {
coverage = get_area_coverage(fEdgeAA, fCorners, pixelCenter);
} else if (fCoverageMode == CoverageMode::kEdgeDistance) {
coverage = get_edge_dist_coverage(fEdgeAA, fCorners, outsets, insets,
pixelCenter);
} else {
SkASSERT(fCoverageMode == CoverageMode::kGPUMesh);
coverage = get_framed_coverage(gpuOutset, gpuOutsetCoverage,
gpuInset, gpuInsetCoverage, gpuDomain,
pixelCenter);
}
SkRect pixelRect = SkRect::MakeXYWH(px, py, 1.f, 1.f);
pixelRect.inset(0.1f, 0.1f);
SkScalar a = 1.f - 0.5f * coverage;
pixelPaint.setColor4f({a, a, a, 1.f}, nullptr);
canvas->drawRect(pixelRect, pixelPaint);
pixelPaint.setColor(coverage > 0.f ? SK_ColorGREEN : SK_ColorRED);
pixelRect.inset(0.38f, 0.38f);
canvas->drawRect(pixelRect, pixelPaint);
}
}
linePaint.setPathEffect(dashes);
// Draw the inset/outset "infinite" lines
if (fCoverageMode == CoverageMode::kEdgeDistance) {
for (int i = 0; i < 4; ++i) {
if (fEdgeAA[i]) {
linePaint.setColor(SK_ColorBLUE);
draw_extended_line(canvas, linePaint, outsets[i * 2], outsets[i * 2 + 1]);
linePaint.setColor(SK_ColorGREEN);
draw_extended_line(canvas, linePaint, insets[i * 2], insets[i * 2 + 1]);
} else {
// Both outset and inset are the same line, so only draw one in cyan
linePaint.setColor(SK_ColorCYAN);
draw_extended_line(canvas, linePaint, outsets[i * 2], outsets[i * 2 + 1]);
}
}
}
linePaint.setPathEffect(nullptr);
// What is tessellated using GrQuadPerEdgeAA
if (fCoverageMode == CoverageMode::kGPUMesh) {
SkPath outsetPath;
outsetPath.addPoly(gpuOutset, 4, true);
linePaint.setColor(SK_ColorBLUE);
canvas->drawPath(outsetPath, linePaint);
SkPath insetPath;
insetPath.addPoly(gpuInset, 4, true);
linePaint.setColor(SK_ColorGREEN);
canvas->drawPath(insetPath, linePaint);
SkPaint domainPaint = linePaint;
domainPaint.setStrokeWidth(2.f / kViewScale);
domainPaint.setPathEffect(dashes);
domainPaint.setColor(SK_ColorMAGENTA);
canvas->drawRect(gpuDomain, domainPaint);
}
// Draw the edges of the true quad as a solid line
SkPath path;
path.addPoly(fCorners, 4, true);
linePaint.setColor(SK_ColorBLACK);
canvas->drawPath(path, linePaint);
} else {
// Draw the edges of the true quad as a solid *red* line
SkPath path;
path.addPoly(fCorners, 4, true);
linePaint.setColor(SK_ColorRED);
linePaint.setPathEffect(nullptr);
canvas->drawPath(path, linePaint);
}
// Draw the four clickable corners as circles
circlePaint.setColor(valid ? SK_ColorBLACK : SK_ColorRED);
for (int i = 0; i < 4; ++i) {
canvas->drawCircle(fCorners[i], 5.f / kViewScale, circlePaint);
}
}
Sample::Click* onFindClickHandler(SkScalar x, SkScalar y, skui::ModifierKey) override;
bool onClick(Sample::Click*) override;
bool onChar(SkUnichar) override;
SkString name() override { return SkString("DegenerateQuad"); }
private:
class Click;
enum class CoverageMode {
kArea, kEdgeDistance, kGPUMesh
};
const SkRect fOuterRect;
SkPoint fCorners[4]; // TL, TR, BR, BL
bool fEdgeAA[4]; // T, R, B, L
CoverageMode fCoverageMode;
bool isValid() const {
SkPath path;
path.addPoly(fCorners, 4, true);
return path.isConvex();
}
void getTessellatedPoints(SkPoint inset[4], SkScalar insetCoverage[4], SkPoint outset[4],
SkScalar outsetCoverage[4], SkRect* domain) const {
// Fixed vertex spec for extracting the picture frame geometry
static const GrQuadPerEdgeAA::VertexSpec kSpec =
{GrQuad::Type::kGeneral, GrQuadPerEdgeAA::ColorType::kNone,
GrQuad::Type::kAxisAligned, false, GrQuadPerEdgeAA::Subset::kNo,
GrAAType::kCoverage, false, GrQuadPerEdgeAA::IndexBufferOption::kPictureFramed};
static const GrQuad kIgnored(SkRect::MakeEmpty());
GrQuadAAFlags flags = GrQuadAAFlags::kNone;
flags |= fEdgeAA[0] ? GrQuadAAFlags::kTop : GrQuadAAFlags::kNone;
flags |= fEdgeAA[1] ? GrQuadAAFlags::kRight : GrQuadAAFlags::kNone;
flags |= fEdgeAA[2] ? GrQuadAAFlags::kBottom : GrQuadAAFlags::kNone;
flags |= fEdgeAA[3] ? GrQuadAAFlags::kLeft : GrQuadAAFlags::kNone;
GrQuad quad = GrQuad::MakeFromSkQuad(fCorners, SkMatrix::I());
float vertices[56]; // 2 quads, with x, y, coverage, and geometry domain (7 floats x 8 vert)
GrQuadPerEdgeAA::Tessellator tessellator(kSpec, (char*) vertices);
tessellator.append(&quad, nullptr, {1.f, 1.f, 1.f, 1.f},
SkRect::MakeEmpty(), flags);
// The first quad in vertices is the inset, then the outset, but they
// are ordered TL, BL, TR, BR so un-interleave coverage and re-arrange
inset[0] = {vertices[0], vertices[1]}; // TL
insetCoverage[0] = vertices[2];
inset[3] = {vertices[7], vertices[8]}; // BL
insetCoverage[3] = vertices[9];
inset[1] = {vertices[14], vertices[15]}; // TR
insetCoverage[1] = vertices[16];
inset[2] = {vertices[21], vertices[22]}; // BR
insetCoverage[2] = vertices[23];
outset[0] = {vertices[28], vertices[29]}; // TL
outsetCoverage[0] = vertices[30];
outset[3] = {vertices[35], vertices[36]}; // BL
outsetCoverage[3] = vertices[37];
outset[1] = {vertices[42], vertices[43]}; // TR
outsetCoverage[1] = vertices[44];
outset[2] = {vertices[49], vertices[50]}; // BR
outsetCoverage[2] = vertices[51];
*domain = {vertices[52], vertices[53], vertices[54], vertices[55]};
}
typedef Sample INHERITED;
};
class DegenerateQuadSample::Click : public Sample::Click {
public:
Click(const SkRect& clamp, int index)
: fOuterRect(clamp)
, fIndex(index) {}
void doClick(SkPoint points[4]) {
if (fIndex >= 0) {
this->drag(&points[fIndex]);
} else {
for (int i = 0; i < 4; ++i) {
this->drag(&points[i]);
}
}
}
private:
SkRect fOuterRect;
int fIndex;
void drag(SkPoint* point) {
SkPoint delta = fCurr - fPrev;
*point += SkPoint::Make(delta.x() / kViewScale, delta.y() / kViewScale);
point->fX = std::min(fOuterRect.fRight, std::max(point->fX, fOuterRect.fLeft));
point->fY = std::min(fOuterRect.fBottom, std::max(point->fY, fOuterRect.fTop));
}
};
Sample::Click* DegenerateQuadSample::onFindClickHandler(SkScalar x, SkScalar y, skui::ModifierKey) {
SkPoint inCTM = SkPoint::Make((x - kViewOffset) / kViewScale, (y - kViewOffset) / kViewScale);
for (int i = 0; i < 4; ++i) {
if ((fCorners[i] - inCTM).length() < 10.f / kViewScale) {
return new Click(fOuterRect, i);
}
}
return new Click(fOuterRect, -1);
}
bool DegenerateQuadSample::onClick(Sample::Click* click) {
Click* myClick = (Click*) click;
myClick->doClick(fCorners);
return true;
}
bool DegenerateQuadSample::onChar(SkUnichar code) {
switch(code) {
case '1':
fEdgeAA[0] = !fEdgeAA[0];
return true;
case '2':
fEdgeAA[1] = !fEdgeAA[1];
return true;
case '3':
fEdgeAA[2] = !fEdgeAA[2];
return true;
case '4':
fEdgeAA[3] = !fEdgeAA[3];
return true;
case 'q':
fCoverageMode = CoverageMode::kArea;
return true;
case 'w':
fCoverageMode = CoverageMode::kEdgeDistance;
return true;
case 'e':
fCoverageMode = CoverageMode::kGPUMesh;
return true;
}
return false;
}
DEF_SAMPLE(return new DegenerateQuadSample(SkRect::MakeWH(4.f, 4.f));)