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skia2/tests/PathMeasureTest.cpp
caryclark b6474dd1a5 fix circular dashing 
Path measure cannot use the same code approach for quadratics
and cubics. Subdividing cubics repeatedly does not result in
subdivided t values, e.g. a quarter circle cubic divided in
half twice does not have a t value equivalent to 1/4.

Instead, always compute the cubic segment from a pair of
t values.

When finding the length of the cubic through recursive measures,
it is enough to carry the point at a given t to the next
subdivision.

(Chrome suppression has landed already.)

R=reed@google.com
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1602153002

Review URL: https://codereview.chromium.org/1602153002
2016-01-19 08:07:50 -08:00

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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.
*/
#include "SkPathMeasure.h"
#include "Test.h"
static void test_small_segment3() {
SkPath path;
const SkPoint pts[] = {
{ 0, 0 },
{ 100000000000.0f, 100000000000.0f }, { 0, 0 }, { 10, 10 },
{ 10, 10 }, { 0, 0 }, { 10, 10 }
};
path.moveTo(pts[0]);
for (size_t i = 1; i < SK_ARRAY_COUNT(pts); i += 3) {
path.cubicTo(pts[i], pts[i + 1], pts[i + 2]);
}
SkPathMeasure meas(path, false);
meas.getLength();
}
static void test_small_segment2() {
SkPath path;
const SkPoint pts[] = {
{ 0, 0 },
{ 100000000000.0f, 100000000000.0f }, { 0, 0 },
{ 10, 10 }, { 0, 0 },
};
path.moveTo(pts[0]);
for (size_t i = 1; i < SK_ARRAY_COUNT(pts); i += 2) {
path.quadTo(pts[i], pts[i + 1]);
}
SkPathMeasure meas(path, false);
meas.getLength();
}
static void test_small_segment() {
SkPath path;
const SkPoint pts[] = {
{ 100000, 100000},
// big jump between these points, makes a big segment
{ 1.0005f, 0.9999f },
// tiny (non-zero) jump between these points
{ SK_Scalar1, SK_Scalar1 },
};
path.moveTo(pts[0]);
for (size_t i = 1; i < SK_ARRAY_COUNT(pts); ++i) {
path.lineTo(pts[i]);
}
SkPathMeasure meas(path, false);
/* this would assert (before a fix) because we added a segment with
the same length as the prev segment, due to the follow (bad) pattern
d = distance(pts[0], pts[1]);
distance += d;
seg->fDistance = distance;
SkASSERT(d > 0); // TRUE
SkASSERT(seg->fDistance > prevSeg->fDistance); // FALSE
This 2nd assert failes because (distance += d) didn't affect distance
because distance >>> d.
*/
meas.getLength();
}
DEF_TEST(PathMeasure, reporter) {
SkPath path;
path.moveTo(0, 0);
path.lineTo(SK_Scalar1, 0);
path.lineTo(SK_Scalar1, SK_Scalar1);
path.lineTo(0, SK_Scalar1);
SkPathMeasure meas(path, true);
SkScalar length = meas.getLength();
SkASSERT(length == SK_Scalar1*4);
path.reset();
path.moveTo(0, 0);
path.lineTo(SK_Scalar1*3, SK_Scalar1*4);
meas.setPath(&path, false);
length = meas.getLength();
REPORTER_ASSERT(reporter, length == SK_Scalar1*5);
path.reset();
path.addCircle(0, 0, SK_Scalar1);
meas.setPath(&path, true);
length = meas.getLength();
// SkDebugf("circle arc-length = %g\n", length);
// Test the behavior following a close not followed by a move.
path.reset();
path.lineTo(SK_Scalar1, 0);
path.lineTo(SK_Scalar1, SK_Scalar1);
path.lineTo(0, SK_Scalar1);
path.close();
path.lineTo(-SK_Scalar1, 0);
meas.setPath(&path, false);
length = meas.getLength();
REPORTER_ASSERT(reporter, length == SK_Scalar1 * 4);
meas.nextContour();
length = meas.getLength();
REPORTER_ASSERT(reporter, length == SK_Scalar1);
SkPoint position;
SkVector tangent;
REPORTER_ASSERT(reporter, meas.getPosTan(SK_ScalarHalf, &position, &tangent));
REPORTER_ASSERT(reporter,
SkScalarNearlyEqual(position.fX,
-SK_ScalarHalf,
0.0001f));
REPORTER_ASSERT(reporter, position.fY == 0);
REPORTER_ASSERT(reporter, tangent.fX == -SK_Scalar1);
REPORTER_ASSERT(reporter, tangent.fY == 0);
// Test degenerate paths
path.reset();
path.moveTo(0, 0);
path.lineTo(0, 0);
path.lineTo(SK_Scalar1, 0);
path.quadTo(SK_Scalar1, 0, SK_Scalar1, 0);
path.quadTo(SK_Scalar1, SK_Scalar1, SK_Scalar1, SK_Scalar1 * 2);
path.cubicTo(SK_Scalar1, SK_Scalar1 * 2,
SK_Scalar1, SK_Scalar1 * 2,
SK_Scalar1, SK_Scalar1 * 2);
path.cubicTo(SK_Scalar1*2, SK_Scalar1 * 2,
SK_Scalar1*3, SK_Scalar1 * 2,
SK_Scalar1*4, SK_Scalar1 * 2);
meas.setPath(&path, false);
length = meas.getLength();
REPORTER_ASSERT(reporter, length == SK_Scalar1 * 6);
REPORTER_ASSERT(reporter, meas.getPosTan(SK_ScalarHalf, &position, &tangent));
REPORTER_ASSERT(reporter,
SkScalarNearlyEqual(position.fX,
SK_ScalarHalf,
0.0001f));
REPORTER_ASSERT(reporter, position.fY == 0);
REPORTER_ASSERT(reporter, tangent.fX == SK_Scalar1);
REPORTER_ASSERT(reporter, tangent.fY == 0);
REPORTER_ASSERT(reporter, meas.getPosTan(2.5f, &position, &tangent));
REPORTER_ASSERT(reporter,
SkScalarNearlyEqual(position.fX, SK_Scalar1, 0.0001f));
REPORTER_ASSERT(reporter,
SkScalarNearlyEqual(position.fY, 1.5f));
REPORTER_ASSERT(reporter, tangent.fX == 0);
REPORTER_ASSERT(reporter, tangent.fY == SK_Scalar1);
REPORTER_ASSERT(reporter, meas.getPosTan(4.5f, &position, &tangent));
REPORTER_ASSERT(reporter,
SkScalarNearlyEqual(position.fX,
2.5f,
0.0001f));
REPORTER_ASSERT(reporter,
SkScalarNearlyEqual(position.fY,
2.0f,
0.0001f));
REPORTER_ASSERT(reporter, tangent.fX == SK_Scalar1);
REPORTER_ASSERT(reporter, tangent.fY == 0);
path.reset();
path.moveTo(0, 0);
path.lineTo(SK_Scalar1, 0);
path.moveTo(SK_Scalar1, SK_Scalar1);
path.moveTo(SK_Scalar1 * 2, SK_Scalar1 * 2);
path.lineTo(SK_Scalar1, SK_Scalar1 * 2);
meas.setPath(&path, false);
length = meas.getLength();
REPORTER_ASSERT(reporter, length == SK_Scalar1);
REPORTER_ASSERT(reporter, meas.getPosTan(SK_ScalarHalf, &position, &tangent));
REPORTER_ASSERT(reporter,
SkScalarNearlyEqual(position.fX,
SK_ScalarHalf,
0.0001f));
REPORTER_ASSERT(reporter, position.fY == 0);
REPORTER_ASSERT(reporter, tangent.fX == SK_Scalar1);
REPORTER_ASSERT(reporter, tangent.fY == 0);
meas.nextContour();
length = meas.getLength();
REPORTER_ASSERT(reporter, length == SK_Scalar1);
REPORTER_ASSERT(reporter, meas.getPosTan(SK_ScalarHalf, &position, &tangent));
REPORTER_ASSERT(reporter,
SkScalarNearlyEqual(position.fX,
1.5f,
0.0001f));
REPORTER_ASSERT(reporter,
SkScalarNearlyEqual(position.fY,
2.0f,
0.0001f));
REPORTER_ASSERT(reporter, tangent.fX == -SK_Scalar1);
REPORTER_ASSERT(reporter, tangent.fY == 0);
test_small_segment();
test_small_segment2();
test_small_segment3();
}
DEF_TEST(PathMeasureConic, reporter) {
SkPoint stdP, hiP, pts[] = {{0,0}, {100,0}, {100,0}};
SkPath p;
p.moveTo(0, 0);
p.conicTo(pts[1], pts[2], 1);
SkPathMeasure stdm(p, false);
REPORTER_ASSERT(reporter, stdm.getPosTan(20, &stdP, nullptr));
p.reset();
p.moveTo(0, 0);
p.conicTo(pts[1], pts[2], 10);
stdm.setPath(&p, false);
REPORTER_ASSERT(reporter, stdm.getPosTan(20, &hiP, nullptr));
REPORTER_ASSERT(reporter, 19.5f < stdP.fX && stdP.fX < 20.5f);
REPORTER_ASSERT(reporter, 19.5f < hiP.fX && hiP.fX < 20.5f);
}
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