fix linear gradient assert, by explicitly clamping
BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1556993003
Review URL: https://codereview.chromium.org/1556993003
diff --git a/src/effects/gradients/SkLinearGradient.cpp b/src/effects/gradients/SkLinearGradient.cpp
index 298466c..4f90c27 100644
--- a/src/effects/gradients/SkLinearGradient.cpp
+++ b/src/effects/gradients/SkLinearGradient.cpp
@@ -668,12 +668,12 @@
}
fx += n * dx;
- count -= n;
- SkASSERT(count >= 0);
+ // fx should now outside of the p0..p1 interval. However, due to float precision loss,
+ // its possible that fx is slightly too small/large, so we clamp it.
if (dx_is_pos) {
- SkASSERT(0 == count || fx >= p1);
+ fx = SkTMax(fx, p1);
} else {
- SkASSERT(0 == count || fx <= p0);
+ fx = SkTMin(fx, p0);
}
ramp<apply_alpha>(dstC, n, c, dc, dither0, dither1);
@@ -683,6 +683,9 @@
if (n & 1) {
SkTSwap(dither0, dither1);
}
+
+ count -= n;
+ SkASSERT(count >= 0);
}
}
diff --git a/tests/GradientTest.cpp b/tests/GradientTest.cpp
index 8d73569..6a277d5 100644
--- a/tests/GradientTest.cpp
+++ b/tests/GradientTest.cpp
@@ -212,9 +212,31 @@
surface->getCanvas()->drawPaint(paint);
}
+// A linear gradient interval can, due to numerical imprecision (likely in the divide)
+// finish an interval with the final fx not landing outside of [p0...p1].
+// The old code had an assert which this test triggered.
+// We now explicitly clamp the resulting fx value.
+static void test_linear_fuzz(skiatest::Reporter* reporter) {
+ SkAutoTUnref<SkSurface> surface(SkSurface::NewRasterN32Premul(1300, 630));
+
+ const SkPoint pts[] = {{ 179.5f, -179.5f }, { 1074.5f, 715.5f }};
+ const SkColor colors[] = { SK_ColorBLACK, SK_ColorWHITE, SK_ColorBLACK, SK_ColorWHITE };
+ const SkScalar pos[] = {0, 0.200000003f, 0.800000012f, 1 };
+
+
+ SkAutoTUnref<SkShader> gradient(
+ SkGradientShader::CreateLinear(pts, colors, pos, 4, SkShader::kClamp_TileMode));
+
+ SkPaint paint;
+ paint.setShader(gradient);
+ SkRect r = {0, 83, 1254, 620};
+ surface->getCanvas()->drawRect(r, paint);
+}
+
DEF_TEST(Gradient, reporter) {
TestGradientShaders(reporter);
TestConstantGradient(reporter);
test_big_grad(reporter);
test_nearly_vertical(reporter);
+ test_linear_fuzz(reporter);
}