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fix fragile cubic stepper, where we want to assert that each tesselated segment

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is monotonically going down, but the finite math we use cannot ensure that...
so we explicitly pin the y-value after it is calculated.

add unittest that exercises the bug/assert that was found on an SVG site



git-svn-id: http://skia.googlecode.com/svn/trunk@5544 2bbb7eff-a529-9590-31e7-b0007b416f81
This commit is contained in:
reed@google.com 2012-09-14 15:18:41 +00:00
parent e21795e277
commit 8cae8358f7
2 changed files with 41 additions and 0 deletions
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7
src/core/SkEdge.cpp
View File

@ -476,6 +476,13 @@ int SkCubicEdge::updateCubic()
newx = fCLastX;
newy = fCLastY;
}
// we want to say SkASSERT(oldy <= newy), but our finite fixedpoint
// doesn't always achieve that, so we have to explicitly pin it here.
if (newy < oldy) {
newy = oldy;
}
success = this->updateLine(oldx, oldy, newx, newy);
oldx = newx;
oldy = newy;

34
tests/PathTest.cpp
View File

@ -6,6 +6,7 @@
* found in the LICENSE file.
*/
#include "Test.h"
#include "SkCanvas.h"
#include "SkPaint.h"
#include "SkPath.h"
#include "SkParse.h"
@ -15,6 +16,38 @@
#include "SkReader32.h"
#include "SkSize.h"
#include "SkWriter32.h"
#include "SkSurface.h"
static SkSurface* new_surface(int w, int h) {
SkImage::Info info = {
w, h, SkImage::kPMColor_ColorType, SkImage::kPremul_AlphaType
};
return SkSurface::NewRaster(info, NULL);
}
// Inspired by http://ie.microsoft.com/testdrive/Performance/Chalkboard/
// which triggered an assert, from a tricky cubic. This test replicates that
// example, so we can ensure that we handle it (in SkEdge.cpp), and don't
// assert in the SK_DEBUG build.
static void test_tricky_cubic(skiatest::Reporter* reporter) {
const SkPoint pts[] = {
{ SkDoubleToScalar(18.8943768), SkDoubleToScalar(129.121277) },
{ SkDoubleToScalar(18.8937435), SkDoubleToScalar(129.121689) },
{ SkDoubleToScalar(18.8950119), SkDoubleToScalar(129.120422) },
{ SkDoubleToScalar(18.5030727), SkDoubleToScalar(129.13121) },
};
SkPath path;
path.moveTo(pts[0]);
path.cubicTo(pts[1], pts[2], pts[3]);
SkPaint paint;
paint.setAntiAlias(true);
SkSurface* surface = new_surface(19, 130);
surface->getCanvas()->drawPath(path, paint);
surface->unref();
}
// Inspired by http://code.google.com/p/chromium/issues/detail?id=141651
//
@ -1590,6 +1623,7 @@ static void TestPath(skiatest::Reporter* reporter) {
test_addPoly(reporter);
test_isfinite(reporter);
test_isfinite_after_transform(reporter);
test_tricky_cubic(reporter);
}
#include "TestClassDef.h"