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Fix convexicator bug

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BUG=crbug.com/412640
R=caryclark@google.com, bsalomon@google.com

Author: robertphillips@google.com

Review URL: https://codereview.chromium.org/573763002
This commit is contained in:
robertphillips 2014-09-16 09:43:31 -07:00 committed by Commit bot
parent a32f1758b7
commit c506e3007e
2 changed files with 69 additions and 16 deletions
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66
src/core/SkPath.cpp
View File

@ -2142,6 +2142,16 @@ void SkPath::validate() const {
static int sign(SkScalar x) { return x < 0; }
#define kValueNeverReturnedBySign 2
enum DirChange {
kLeft_DirChange,
kRight_DirChange,
kStraight_DirChange,
kBackwards_DirChange,
kInvalid_DirChange
};
static bool almost_equal(SkScalar compA, SkScalar compB) {
// The error epsilon was empirically derived; worse case round rects
// with a mid point outset by 2x float epsilon in tests had an error
@ -2156,13 +2166,37 @@ static bool almost_equal(SkScalar compA, SkScalar compB) {
return aBits < bBits + epsilon && bBits < aBits + epsilon;
}
static DirChange direction_change(const SkPoint& lastPt, const SkVector& curPt,
const SkVector& lastVec, const SkVector& curVec) {
SkScalar cross = SkPoint::CrossProduct(lastVec, curVec);
SkScalar smallest = SkTMin(curPt.fX, SkTMin(curPt.fY, SkTMin(lastPt.fX, lastPt.fY)));
SkScalar largest = SkTMax(curPt.fX, SkTMax(curPt.fY, SkTMax(lastPt.fX, lastPt.fY)));
largest = SkTMax(largest, -smallest);
if (!almost_equal(largest, largest + cross)) {
int sign = SkScalarSignAsInt(cross);
if (sign) {
return (1 == sign) ? kRight_DirChange : kLeft_DirChange;
}
}
if (!SkScalarNearlyZero(lastVec.lengthSqd(), SK_ScalarNearlyZero*SK_ScalarNearlyZero) &&
!SkScalarNearlyZero(curVec.lengthSqd(), SK_ScalarNearlyZero*SK_ScalarNearlyZero) &&
lastVec.dot(curVec) < 0.0f) {
return kBackwards_DirChange;
}
return kStraight_DirChange;
}
// only valid for a single contour
struct Convexicator {
Convexicator()
: fPtCount(0)
, fConvexity(SkPath::kConvex_Convexity)
, fDirection(SkPath::kUnknown_Direction) {
fSign = 0;
fExpectedDir = kInvalid_DirChange;
// warnings
fLastPt.set(0, 0);
fCurrPt.set(0, 0);
@ -2221,20 +2255,28 @@ struct Convexicator {
private:
void addVec(const SkVector& vec) {
SkASSERT(vec.fX || vec.fY);
SkScalar cross = SkPoint::CrossProduct(fLastVec, vec);
SkScalar smallest = SkTMin(fCurrPt.fX, SkTMin(fCurrPt.fY, SkTMin(fLastPt.fX, fLastPt.fY)));
SkScalar largest = SkTMax(fCurrPt.fX, SkTMax(fCurrPt.fY, SkTMax(fLastPt.fX, fLastPt.fY)));
largest = SkTMax(largest, -smallest);
if (!almost_equal(largest, largest + cross)) {
int sign = SkScalarSignAsInt(cross);
if (0 == fSign) {
fSign = sign;
fDirection = (1 == sign) ? SkPath::kCW_Direction : SkPath::kCCW_Direction;
} else if (sign && fSign != sign) {
DirChange dir = direction_change(fLastPt, fCurrPt, fLastVec, vec);
switch (dir) {
case kLeft_DirChange: // fall through
case kRight_DirChange:
if (kInvalid_DirChange == fExpectedDir) {
fExpectedDir = dir;
fDirection = (kRight_DirChange == dir) ? SkPath::kCW_Direction
: SkPath::kCCW_Direction;
} else if (dir != fExpectedDir) {
fConvexity = SkPath::kConcave_Convexity;
fDirection = SkPath::kUnknown_Direction;
}
fLastVec = vec;
break;
case kStraight_DirChange:
break;
case kBackwards_DirChange:
fLastVec = vec;
break;
case kInvalid_DirChange:
SkFAIL("Use of invalid direction change flag");
break;
}
}
@ -2244,7 +2286,7 @@ private:
// value with the current vec is deemed to be of a significant value.
SkVector fLastVec, fFirstVec;
int fPtCount; // non-degenerate points
int fSign;
DirChange fExpectedDir;
SkPath::Convexity fConvexity;
SkPath::Direction fDirection;
int fDx, fDy, fSx, fSy;

11
tests/PathTest.cpp
View File

@ -1195,6 +1195,17 @@ static void test_convexity2(skiatest::Reporter* reporter) {
stroke.applyToPath(&strokedSin, strokedSin);
check_convexity(reporter, strokedSin, SkPath::kConcave_Convexity);
check_direction(reporter, strokedSin, kDontCheckDir);
// http://crbug.com/412640
SkPath degenerateConcave;
degenerateConcave.moveTo(148.67912f, 191.875f);
degenerateConcave.lineTo(470.37695f, 7.5f);
degenerateConcave.lineTo(148.67912f, 191.875f);
degenerateConcave.lineTo(41.446522f, 376.25f);
degenerateConcave.lineTo(-55.971577f, 460.0f);
degenerateConcave.lineTo(41.446522f, 376.25f);
check_convexity(reporter, degenerateConcave, SkPath::kConcave_Convexity);
check_direction(reporter, degenerateConcave, SkPath::kUnknown_Direction);
}
static void check_convex_bounds(skiatest::Reporter* reporter, const SkPath& p,