This is working towards fixing all bugs around simplifying the tiger.
This installment simplifies the point-t intersection list as it is built rather than doing the analysis once the intersections are complete. This avoids getting the list in an inconsistent state and makes coincident checks faster and more stable.
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BUG=skia:5131
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This removes the notion of keeping track of every different t value
that resolves to the same or a similar point. Other fixes make
this concept unnecessary, and removing it simplifies the code.
This removes an allocation, and speeds up paths with many
overlapping curves.
As a bonus, four fuzzer tests that failed before now succeed.
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Fix another fuzzer bug.
Some PathOps asserts only make sense if the incoming data is
well-behaved. Well-behaved tests set debugging state to
trigger these additional asserts.
Formalize this by creating macros similar to SkASSERT that
check to see if the assert should be skipped.
TBR=reed@google.com
BUG=629962
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Most changes stem from working on an examples bracketed
by #if DEBUG_UNDER_DEVELOPMENT // tiger
These exposed many problems with coincident curves,
as well as errors throughout the code.
Fixing these errors also fixed a number of fuzzer-inspired
bug reports.
* Line/Curve Intersections
Check to see if the end of the line nearly intersects
the curve. This was a FIXME in the old code.
* Performance
Use a central chunk allocator.
Plumb the allocator into the global variable state
so that it can be shared. (Note that 'SkGlobalState'
is allocated on the stack and is visible to children
functions but not other threads.)
* Refactor
Let SkOpAngle grow up from a structure to a class.
Let SkCoincidentSpans grow up from a structure to a class.
Rename enum Alias to AliasMatch.
* Coincidence Rewrite
Add more debugging to coincidence detection.
Parallel debugging routines have read-only logic to report
the current coincidence state so that steps through the
logic can expose whether things got better or worse.
More functions can error-out and cause the pathops
engine to non-destructively exit.
* Accuracy
Remove code that adjusted point locations. Instead,
offset the curve part so that sorted curves all use
the same origin.
Reduce the size (and influence) of magic numbers.
* Testing
The debug suite with verify and the full release suite
./out/Debug/pathops_unittest -v -V
./out/Release/pathops_unittest -v -V -x
expose one error. That error is captured as cubics_d3.
This error exists in the checked in code as well.
BUG=skia:
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Fail out in a couple of new places when the input data is very
large and exceeds the limits of the pathops machinery.
Most of the change here plumbs in a way to exclude an assert in
one of these exceptional cases. The current SkAddIntersection
implementation and the inner functions it calls has no way to
report an error to the root caller for an early exit, so rather
than add that in, exclude the assert when the test that would
trigger it runs (allowing the test to otherwise ensure that it
properly fails).
TBR=reed@google.com
BUG=617586,617635
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This fix is a tradeoff. It changes intersection to
treat a case where one coincident run is intersected at one point
and the other edge is not as continuing to be a span.
The old code tried to treat this as a single point.
The old code is probably right, but this change alone
made the data structures inconsistent. Later, extending
the coincident runs would fail by incorrectly discarding
the single point intersection.
As a result, this fixes the security test and one other, but
makes a different test fail. Isolating the failure uncovered
a reduced case that fails with and without the change, so
there are more serious problems here. Those problems are
addressed in a separate CL.
Many of the test edits below remove ill-thought out debugging
messaging that fire off global state, which isn't usable
in a multi-threaded test environment.
In the end, with this fix, all existing tests (modulo one
new failure and one new non-failure) pass in debug and
in the extended release test suites.
TBR=reed@google.com
BUG=614248
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If one path is empty and the other has extreme values, the
intermediate coincident paths cannot be resolved, but triggers
an assert that a data structure unexpectedly has zero-length.
Tunnel this failure back up to the top and return that the
entire path op fails.
A future optimization could detect the empty path and avoid
this, allowing the op to succeed -- not sure that it's worth
the additional logic though.
TBR=reed@google.com
BUG=535151
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Iterating through the 903K skps that represent the
imagable 1M top web pages triggers a number of
bugs, some of which are addressed here.
Some web pages trigger intersecting cubic
representations of arc with their conic
counterparts. This exposed a flaw in coincident
detection that caused an infinite loop. The loop
alternatively extended the coincident section and,
determining the that the bounds of the curve pairs
did not overlap, deleted the extension.
Track the number of times the coincident detection
is called, and if it exceeds an empirically found
limit, assume that the curves are coincident and
force it to be so.
The loop count limit can be determined by enabling
DEBUG_T_SECT_LOOP_COUNT and running all tests. The
largest count is reported on completion.
Another class of bugs was caused by concident
detection duplicating nearly identical points that
had been merged earlier. To track these bugs, the
'handle coincidence' code was duplicated as a
const debug variety that reported if one of a
dozen or so irregularities are present; then it is
easier to see when a block of code that fixes one
irregularity regresses another.
Creating the debug const code version exposed some
non-debug code that could be const, and some that
was experimental and could be removed. Set
DEBUG_COINCIDENCE to track coincidence health and
handling.
For running on Chrome, DEBUG_VERIFY checks the
result of pathops against the same operation
using SkRegion to verify that the results are
nearly the same.
When visualizing the pathops work using
tools/pathops_visualizer.htm, set
DEBUG_DUMP_ALIGNMENT to see the curves after
they've been aligned for coincidence.
Other bugs fixed include detecting when a
section of a pair of curves have devolved into
lines and are coincident.
TBR=reed@google.com
Review URL: https://codereview.chromium.org/1394503003
crbug.com/526025 includes a minimized SVG test case.
Translating that test case into native code (fuzzTNG)
did not reproduce the bug. That test case should
have not been included with skia issue 1323813003,
and is deleted here.
Running the minimal test case in a modified version
of chrome isolated the bug. The modified version
generated the test fuzz763_3 with the edit
#define DEBUGGING_PATHOPS_FROM_HOST 1
in src/pathops/SkPathopsOp.cpp line 188.
Rename fuzz763_3 to issue_526025 to associate the test
with the bug. Note that the bug contains the body of the
CL in comment $5.
R=reed@google.com
Review URL: https://codereview.chromium.org/1315503005
The list of intersection points on a curve segment may have
entries that can be safely removed when nearby points have
nearly the same t value and point value. When a path includes
very large curves as well as small ones, as is the case with
this fuzzer, additional points may lie between the similar
points that do not meet the nearby criteria.
After merging the nearby point with its doppelganger,
SkOpSegment::moveNearby() unnecessarily set the doppelganger's
next pointer to the one following the nearby point. While
this usually has no effect, since the merge already updated
the linked list, the explicit call removes the additional
outlier points from the segment.
TBR=reed@google.com
BUG=526025
Review URL: https://codereview.chromium.org/1323813003
If a curve has the identical start and control points, the
initial or final tangent can't be trivally determined. The
perpendicular to the tangent is used to measure coincidence.
Add logic for cubics, quadratics, and conics, to use the
secondary control points or the end points if the initial
control point alone can't determine the tangent.
Add debugging (currently untriggered by exhaustive testing)
to detect zero-length tangents which are not at the curve
endpoints.
Increase the number of temporary intersecions gathered from
10 to 12 but reduce the max passed in by cubic intersection from
27 to 12. Also, add checks if the max passed exceeds the
storage allocated.
When cleaning up parallel lines, choose the intersection which
is on the end of both segments over the intersection which
is on the end of a single segment.
TBR=reed@google.com
BUG=425140,516266
Review URL: https://codereview.chromium.org/1288863004
Improve line/curve coincident detection and resolution. This fixed the remaining simple failures.
When an edge is unsortable, use the ray intersection to determine the angles' winding.
Deal with degenerate segments.
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BUG=skia:3588,skia:3762
Review URL: https://codereview.chromium.org/1140813002
This replacement shoots axis-aligned rays through all intersecting edges to find the outermost one either horizontally or vertically. The resulting code is smaller and twice as fast.
To support this, most of the horizontal / vertical intersection code was rewritten and standardized, and old code supporting the top-directed winding was deleted.
Contours were pointed to by an SkTDArray. Instead, put them in a linked list, and designate the list head with its own class to ensure that methods that take lists of contours start at the top. This change removed a large percentage of memory allocations used by path ops.
TBR=reed@google.com
BUG=skia:3588
Review URL: https://codereview.chromium.org/1111333002
