Harden LinearGradient4fContext
Three distinct issues exposed by Fuzzer:
1) truncating the flags to 8 bits may trip the assert in SkToU8
Since clients can pass in any garbage, we cannot assume it fits in 8
bits. Just static_cast<> instead.
2) vertical gradients with dx == -0.0 don't trigger interval inversion.
For dx < 0 we want reversed intervals. But, alas, -0.0 < 0 == false
(thanks, Ob^WIEEE 754!). Use signbit() instead.
3) half closed range checking needs to be inverted for reversed
intervals.
Normally we check for [p0, p1), but for reversed intervals (p1 < p0) we
want to check for [p1, p0), and not (p1, p0]. Adjust the logic
accordingly.
BUG=skia:5647
R=reed@google.com,kjlubick@google.com
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2349153004
Review-Url: https://codereview.chromium.org/2349153004
diff --git a/src/effects/gradients/Sk4fLinearGradient.cpp b/src/effects/gradients/Sk4fLinearGradient.cpp
index dc6e530..cd1f770 100644
--- a/src/effects/gradients/Sk4fLinearGradient.cpp
+++ b/src/effects/gradients/Sk4fLinearGradient.cpp
@@ -100,12 +100,13 @@
return f < 0 ? f + 2 : f;
}
-// true when x is in [k1,k2)
+// true when x is in [k1,k2), or [k2, k1) when the interval is reversed.
+// TODO(fmalita): hoist the reversed interval check out of this helper.
bool in_range(SkScalar x, SkScalar k1, SkScalar k2) {
SkASSERT(k1 != k2);
return (k1 < k2)
- ? (x >= k1 && x < k2)
- : (x >= k2 && x < k1);
+ ? (x >= k1 && x < k2)
+ : (x > k2 && x <= k1);
}
} // anonymous namespace
@@ -116,7 +117,7 @@
: INHERITED(shader, rec) {
// Our fast path expects interval points to be monotonically increasing in x.
- const bool reverseIntervals = this->isFast() && fDstToPos.getScaleX() < 0;
+ const bool reverseIntervals = this->isFast() && signbit(fDstToPos.getScaleX());
this->buildIntervals(shader, rec, reverseIntervals);
SkASSERT(fIntervals.count() > 0);
@@ -290,6 +291,7 @@
, fDx(dx)
, fIsVertical(is_vertical)
{
+ SkASSERT(fAdvX >= 0);
SkASSERT(firstInterval <= lastInterval);
SkASSERT(in_range(fx, i->fP0, i->fP1));
this->compute_interval_props(fx - i->fP0);