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Compute slope using fSnappedY

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If we use the oldy and dy directly as we did previously, the slope could
be very different from (newSnappedX - fSnappedX) / (newSnappedY -
fSnappedY) in the updateLine when the edge made a lot of updates with
small dy but large dx. That will cause bug skia:5995

BUG=skia:5995

Change-Id: If521976ed87195dfea5961afd58bedb98447c568
Reviewed-on: https://skia-review.googlesource.com/5269
Reviewed-by: Cary Clark <caryclark@google.com>
Commit-Queue: Yuqian Li <liyuqian@google.com>
This commit is contained in:
Yuqian Li 2016-11-29 10:27:16 -05:00 committed by Skia Commit-Bot
parent cdb4d3c81d
commit 9939bd6454
2 changed files with 21 additions and 4 deletions
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11
src/core/SkAnalyticEdge.cpp
View File

@ -105,10 +105,14 @@ bool SkAnalyticQuadraticEdge::updateQuadratic() {
{
newx = oldx + (dx >> shift);
newy = oldy + (dy >> shift);
SkFDot6 diffY = (newy - fSnappedY) >> 10;
slope = diffY ? QuickSkFDot6Div((newx - fSnappedX) >> 10, diffY) : SK_MaxS32;
#ifdef SK_ANALYTIC_AA_GUARD
slope = dy >> 10 > 0 ? QuickSkFDot6Div(dx >> 10, dy >> 10) : SK_MaxS32;
#endif
if (SkAbs32(dy) >= SK_Fixed1 * 2) { // only snap when dy is large enough
newSnappedY = SkTMin<SkFixed>(fQEdge.fQLastY, SkFixedRoundToFixed(newy));
newSnappedX = newx + SkFixedMul(slope, newSnappedY - newy);
newSnappedX = newx - SkFixedMul(slope, newy - newSnappedY);
} else {
newSnappedY = SkTMin(fQEdge.fQLastY, snapY(newy));
newSnappedX = newx;
@ -122,9 +126,8 @@ bool SkAnalyticQuadraticEdge::updateQuadratic() {
newy = fQEdge.fQLastY;
newSnappedY = newy;
newSnappedX = newx;
slope = (newSnappedY - fSnappedY) >> 10
? QuickSkFDot6Div((newx - fSnappedX) >> 10, (newy - fSnappedY) >> 10)
: SK_MaxS32;
SkFDot6 diffY = (newy - fSnappedY) >> 10;
slope = diffY ? QuickSkFDot6Div((newx - fSnappedX) >> 10, diffY) : SK_MaxS32;
}
if (slope < SK_MaxS32) {
success = this->updateLine(fSnappedX, fSnappedY, newSnappedX, newSnappedY, slope);

14
tests/PathTest.cpp
View File

@ -242,6 +242,19 @@ static void test_path_crbugskia2820(skiatest::Reporter* reporter) {//GrContext*
stroke.applyToPath(&path, path);
}
static void test_path_crbugskia5995() {
auto surface(SkSurface::MakeRasterN32Premul(500, 500));
SkCanvas* canvas = surface->getCanvas();
SkPaint paint;
paint.setAntiAlias(true);
SkPath path;
path.moveTo(SkBits2Float(0x40303030), SkBits2Float(0x3e303030)); // 2.75294f, 0.172059f
path.quadTo(SkBits2Float(0x41d63030), SkBits2Float(0x30303030), SkBits2Float(0x41013030),
SkBits2Float(0x00000000)); // 26.7735f, 6.40969e-10f, 8.07426f, 0
path.moveTo(SkBits2Float(0x00000000), SkBits2Float(0x00000000)); // 0, 0
canvas->drawPath(path, paint);
}
static void make_path0(SkPath* path) {
// from * https://code.google.com/p/skia/issues/detail?id=1706
@ -4528,6 +4541,7 @@ DEF_TEST(Paths, reporter) {
test_dump(reporter);
test_path_crbug389050(reporter);
test_path_crbugskia2820(reporter);
test_path_crbugskia5995();
test_skbug_3469(reporter);
test_skbug_3239(reporter);
test_bounds_crbug_513799(reporter);