Fix GrReducedClip.cpp: assertion failure surrounding tiny query bounds

Some assertions cannot be relied upon due to FP error.

Bug: skia:5990
Change-Id: I32445b320b9100ae2f80d2f762707d823da77805
Reviewed-on: https://skia-review.googlesource.com/18602
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Chris Dalton <csmartdalton@google.com>

3 files changed, 50 insertions, 9 deletions

diff --git a/src/gpu/GrClip.h b/src/gpu/GrClip.h
index c44653baad..2e247c82f2 100644
--- a/src/gpu/GrClip.h
+++ b/src/gpu/GrClip.h
@@ -90,12 +90,16 @@ public:
      */
     template <typename TRect>
     constexpr static bool IsOutsideClip(const TRect& outerClipBounds, const SkRect& queryBounds) {
-        return outerClipBounds.fRight - outerClipBounds.fLeft <= kBoundsTolerance ||
-               outerClipBounds.fBottom - outerClipBounds.fTop <= kBoundsTolerance ||
-               outerClipBounds.fLeft >= queryBounds.fRight - kBoundsTolerance ||
-               outerClipBounds.fTop >= queryBounds.fBottom - kBoundsTolerance ||
-               outerClipBounds.fRight <= queryBounds.fLeft + kBoundsTolerance ||
-               outerClipBounds.fBottom <= queryBounds.fTop + kBoundsTolerance;
+        return
+            // Is the clip so small that it is effectively empty?
+            outerClipBounds.fRight - outerClipBounds.fLeft <= kBoundsTolerance ||
+            outerClipBounds.fBottom - outerClipBounds.fTop <= kBoundsTolerance ||
+
+            // Are the query bounds effectively outside the clip?
+            outerClipBounds.fLeft >= queryBounds.fRight - kBoundsTolerance ||
+            outerClipBounds.fTop >= queryBounds.fBottom - kBoundsTolerance ||
+            outerClipBounds.fRight <= queryBounds.fLeft + kBoundsTolerance ||
+            outerClipBounds.fBottom <= queryBounds.fTop + kBoundsTolerance;
     }
 
     /**
diff --git a/src/gpu/GrReducedClip.cpp b/src/gpu/GrReducedClip.cpp
index b7ffa7b26f..8c98ac1c71 100644
--- a/src/gpu/GrReducedClip.cpp
+++ b/src/gpu/GrReducedClip.cpp
@@ -45,7 +45,7 @@ GrReducedClip::GrReducedClip(const SkClipStack& stack, const SkRect& queryBounds
     bool iior;
     stack.getBounds(&stackBounds, &stackBoundsType, &iior);
 
-    if (stackBounds.isEmpty() || GrClip::IsOutsideClip(stackBounds, queryBounds)) {
+    if (GrClip::IsOutsideClip(stackBounds, queryBounds)) {
         bool insideOut = SkClipStack::kInsideOut_BoundsType == stackBoundsType;
         fInitialState = insideOut ? InitialState::kAllIn : InitialState::kAllOut;
         return;
@@ -72,7 +72,10 @@ GrReducedClip::GrReducedClip(const SkClipStack& stack, const SkRect& queryBounds
         SkRect tightBounds;
         SkAssertResult(tightBounds.intersect(stackBounds, queryBounds));
         fIBounds = GrClip::GetPixelIBounds(tightBounds);
-        SkASSERT(!fIBounds.isEmpty()); // Empty should have been blocked by IsOutsideClip above.
+        if (fIBounds.isEmpty()) {
+            fInitialState = InitialState::kAllOut;
+            return;
+        }
         fHasIBounds = true;
 
         // Implement the clip with an AA rect element.
@@ -92,7 +95,10 @@ GrReducedClip::GrReducedClip(const SkClipStack& stack, const SkRect& queryBounds
     }
 
     fIBounds = GrClip::GetPixelIBounds(tighterQuery);
-    SkASSERT(!fIBounds.isEmpty()); // Empty should have been blocked by IsOutsideClip above.
+    if (fIBounds.isEmpty()) {
+        fInitialState = InitialState::kAllOut;
+        return;
+    }
     fHasIBounds = true;
 
     // Now that we have determined the bounds to use and filtered out the trivial cases, call the
diff --git a/tests/ClipStackTest.cpp b/tests/ClipStackTest.cpp
index e0df2ca902..1cb644a80f 100644
--- a/tests/ClipStackTest.cpp
+++ b/tests/ClipStackTest.cpp
@@ -1357,6 +1357,36 @@ static void test_reduced_clip_stack_aa(skiatest::Reporter* reporter) {
     }
 }
 
+static void test_tiny_query_bounds_assertion_bug(skiatest::Reporter* reporter) {
+    // https://bugs.chromium.org/p/skia/issues/detail?id=5990
+    const SkRect clipBounds = SkRect::MakeXYWH(1.5f, 100, 1000, 1000);
+
+    SkClipStack rectStack;
+    rectStack.clipRect(clipBounds, SkMatrix::I(), kIntersect_SkClipOp, true);
+
+    SkPath clipPath;
+    clipPath.moveTo(clipBounds.left(), clipBounds.top());
+    clipPath.quadTo(clipBounds.right(), clipBounds.top(),
+                    clipBounds.right(), clipBounds.bottom());
+    clipPath.quadTo(clipBounds.left(), clipBounds.bottom(),
+                    clipBounds.left(), clipBounds.top());
+    SkClipStack pathStack;
+    pathStack.clipPath(clipPath, SkMatrix::I(), kIntersect_SkClipOp, true);
+
+    for (const SkClipStack& stack : {rectStack, pathStack}) {
+        for (SkRect queryBounds : {SkRect::MakeXYWH(53, 60, GrClip::kBoundsTolerance, 1000),
+                                   SkRect::MakeXYWH(53, 60, GrClip::kBoundsTolerance/2, 1000),
+                                   SkRect::MakeXYWH(53, 160, 1000, GrClip::kBoundsTolerance),
+                                   SkRect::MakeXYWH(53, 160, 1000, GrClip::kBoundsTolerance/2)}) {
+            const GrReducedClip reduced(stack, queryBounds);
+            REPORTER_ASSERT(reporter, !reduced.hasIBounds());
+            REPORTER_ASSERT(reporter, reduced.elements().isEmpty());
+            REPORTER_ASSERT(reporter,
+                            GrReducedClip::InitialState::kAllOut == reduced.initialState());
+        }
+    }
+}
+
 #endif
 
 DEF_TEST(ClipStack, reporter) {
@@ -1409,6 +1439,7 @@ DEF_TEST(ClipStack, reporter) {
     test_reduced_clip_stack_genid(reporter);
     test_reduced_clip_stack_no_aa_crash(reporter);
     test_reduced_clip_stack_aa(reporter);
+    test_tiny_query_bounds_assertion_bug(reporter);
 #endif
 }