Improve the compositing reasons when squashing fails

Source/platform/graphics/CompositingReasons.h

Index: Source/platform/graphics/CompositingReasons.h
diff --git a/Source/platform/graphics/CompositingReasons.h b/Source/platform/graphics/CompositingReasons.h
index 9f0bfd3c425915227ec6060417f2a2b46f7ceae7..b4aa6f895c2036b88b3ecf6a18e15c3124a1a990 100644
--- a/Source/platform/graphics/CompositingReasons.h
+++ b/Source/platform/graphics/CompositingReasons.h
@@ -10,67 +10,73 @@
 
 namespace WebCore {
 
-const uint64_t CompositingReasonNone                                   = 0;
-const uint64_t CompositingReasonAll                                    = ~static_cast<uint64_t>(0);
+const uint64_t CompositingReasonNone                                     = 0;
+const uint64_t CompositingReasonAll                                      = ~static_cast<uint64_t>(0);
 
 // Intrinsic reasons that can be known right away by the layer
-const uint64_t CompositingReason3DTransform                            = UINT64_C(1) << 0;
-const uint64_t CompositingReasonVideo                                  = UINT64_C(1) << 1;
-const uint64_t CompositingReasonCanvas                                 = UINT64_C(1) << 2;
-const uint64_t CompositingReasonPlugin                                 = UINT64_C(1) << 3;
-const uint64_t CompositingReasonIFrame                                 = UINT64_C(1) << 4;
-const uint64_t CompositingReasonBackfaceVisibilityHidden               = UINT64_C(1) << 5;
-const uint64_t CompositingReasonActiveAnimation                        = UINT64_C(1) << 6;
-const uint64_t CompositingReasonTransitionProperty                     = UINT64_C(1) << 7;
-const uint64_t CompositingReasonFilters                                = UINT64_C(1) << 8;
-const uint64_t CompositingReasonPositionFixed                          = UINT64_C(1) << 9;
-// Bit 10 is available.
-const uint64_t CompositingReasonOverflowScrollingTouch                 = UINT64_C(1) << 11;
-const uint64_t CompositingReasonOverflowScrollingParent                = UINT64_C(1) << 12;
-const uint64_t CompositingReasonOutOfFlowClipping                      = UINT64_C(1) << 13;
-const uint64_t CompositingReasonVideoOverlay                           = UINT64_C(1) << 14;
-const uint64_t CompositingReasonWillChangeCompositingHint              = UINT64_C(1) << 15;
-// Bit 16 is available.
+const uint64_t CompositingReason3DTransform                              = UINT64_C(1) << 0;
+const uint64_t CompositingReasonVideo                                    = UINT64_C(1) << 1;
+const uint64_t CompositingReasonCanvas                                   = UINT64_C(1) << 2;
+const uint64_t CompositingReasonPlugin                                   = UINT64_C(1) << 3;
+const uint64_t CompositingReasonIFrame                                   = UINT64_C(1) << 4;
+const uint64_t CompositingReasonBackfaceVisibilityHidden                 = UINT64_C(1) << 5;
+const uint64_t CompositingReasonActiveAnimation                          = UINT64_C(1) << 6;
+const uint64_t CompositingReasonTransitionProperty                       = UINT64_C(1) << 7;
+const uint64_t CompositingReasonFilters                                  = UINT64_C(1) << 8;
+const uint64_t CompositingReasonPositionFixed                            = UINT64_C(1) << 9;
+const uint64_t CompositingReasonOverflowScrollingTouch                   = UINT64_C(1) << 10;
+const uint64_t CompositingReasonOverflowScrollingParent                  = UINT64_C(1) << 11;
+const uint64_t CompositingReasonOutOfFlowClipping                        = UINT64_C(1) << 12;
+const uint64_t CompositingReasonVideoOverlay                             = UINT64_C(1) << 13;
+const uint64_t CompositingReasonWillChangeCompositingHint                = UINT64_C(1) << 14;
 
 // Overlap reasons that require knowing what's behind you in paint-order before knowing the answer
-const uint64_t CompositingReasonAssumedOverlap                         = UINT64_C(1) << 17;
-const uint64_t CompositingReasonOverlap                                = UINT64_C(1) << 18;
-const uint64_t CompositingReasonNegativeZIndexChildren                 = UINT64_C(1) << 19;
-const uint64_t CompositingReasonNoSquashingTargetFound                 = UINT64_C(1) << 20;
+const uint64_t CompositingReasonAssumedOverlap                           = UINT64_C(1) << 15;
+const uint64_t CompositingReasonOverlap                                  = UINT64_C(1) << 16;
+const uint64_t CompositingReasonNegativeZIndexChildren                   = UINT64_C(1) << 17;
+const uint64_t CompositingReasonScrollsWithRespectToSquashingLayer       = UINT64_C(1) << 18;
+const uint64_t CompositingReasonSquashingSparsityExceeded                = UINT64_C(1) << 19;
+const uint64_t CompositingReasonSquashingClippingContainerMismatch       = UINT64_C(1) << 20;
+const uint64_t CompositingReasonSquashingOpacityAncestorMismatch         = UINT64_C(1) << 21;
+const uint64_t CompositingReasonSquashingTransformAncestorMismatch       = UINT64_C(1) << 22;
+const uint64_t CompositingReasonSquashingFilterAncestorMismatch          = UINT64_C(1) << 23;
+const uint64_t CompositingReasonSquashingWouldBreakPaintOrder            = UINT64_C(1) << 24;
+const uint64_t CompositingReasonSquashingVideoIsDisallowed               = UINT64_C(1) << 25;
+const uint64_t CompositingReasonSquashedLayerClipsCompositingDescendants = UINT64_C(1) << 26;
 
 // Subtree reasons that require knowing what the status of your subtree is before knowing the answer
-const uint64_t CompositingReasonTransformWithCompositedDescendants     = UINT64_C(1) << 21;
-const uint64_t CompositingReasonOpacityWithCompositedDescendants       = UINT64_C(1) << 22;
-const uint64_t CompositingReasonMaskWithCompositedDescendants          = UINT64_C(1) << 23;
-const uint64_t CompositingReasonReflectionWithCompositedDescendants    = UINT64_C(1) << 24;
-const uint64_t CompositingReasonFilterWithCompositedDescendants        = UINT64_C(1) << 25;
-const uint64_t CompositingReasonBlendingWithCompositedDescendants      = UINT64_C(1) << 26;
-const uint64_t CompositingReasonClipsCompositingDescendants            = UINT64_C(1) << 27;
-const uint64_t CompositingReasonPerspectiveWith3DDescendants           = UINT64_C(1) << 28;
-const uint64_t CompositingReasonPreserve3DWith3DDescendants            = UINT64_C(1) << 29;
-const uint64_t CompositingReasonReflectionOfCompositedParent           = UINT64_C(1) << 30;
-const uint64_t CompositingReasonIsolateCompositedDescendants           = UINT64_C(1) << 31;
+const uint64_t CompositingReasonTransformWithCompositedDescendants       = UINT64_C(1) << 27;
+const uint64_t CompositingReasonOpacityWithCompositedDescendants         = UINT64_C(1) << 28;
+const uint64_t CompositingReasonMaskWithCompositedDescendants            = UINT64_C(1) << 29;
+const uint64_t CompositingReasonReflectionWithCompositedDescendants      = UINT64_C(1) << 30;
+const uint64_t CompositingReasonFilterWithCompositedDescendants          = UINT64_C(1) << 31;
+const uint64_t CompositingReasonBlendingWithCompositedDescendants        = UINT64_C(1) << 32;
+const uint64_t CompositingReasonClipsCompositingDescendants              = UINT64_C(1) << 33;
+const uint64_t CompositingReasonPerspectiveWith3DDescendants             = UINT64_C(1) << 34;
+const uint64_t CompositingReasonPreserve3DWith3DDescendants              = UINT64_C(1) << 35;
+const uint64_t CompositingReasonReflectionOfCompositedParent             = UINT64_C(1) << 36;
+const uint64_t CompositingReasonIsolateCompositedDescendants             = UINT64_C(1) << 37;
 
 // The root layer is a special case that may be forced to be a layer, but also it needs to be
 // a layer if anything else in the subtree is composited.
-const uint64_t CompositingReasonRoot                                   = UINT64_C(1) << 32;
+const uint64_t CompositingReasonRoot                                     = UINT64_C(1) << 38;
 
 // CompositedLayerMapping internal hierarchy reasons
-const uint64_t CompositingReasonLayerForAncestorClip                   = UINT64_C(1) << 33;
-const uint64_t CompositingReasonLayerForDescendantClip                 = UINT64_C(1) << 34;
-const uint64_t CompositingReasonLayerForPerspective                    = UINT64_C(1) << 35;
-const uint64_t CompositingReasonLayerForHorizontalScrollbar            = UINT64_C(1) << 36;
-const uint64_t CompositingReasonLayerForVerticalScrollbar              = UINT64_C(1) << 37;
-const uint64_t CompositingReasonLayerForScrollCorner                   = UINT64_C(1) << 38;
-const uint64_t CompositingReasonLayerForScrollingContents              = UINT64_C(1) << 39;
-const uint64_t CompositingReasonLayerForScrollingContainer             = UINT64_C(1) << 40;
-const uint64_t CompositingReasonLayerForSquashingContents              = UINT64_C(1) << 41;
-const uint64_t CompositingReasonLayerForSquashingContainer             = UINT64_C(1) << 42;
-const uint64_t CompositingReasonLayerForForeground                     = UINT64_C(1) << 43;
-const uint64_t CompositingReasonLayerForBackground                     = UINT64_C(1) << 44;
-const uint64_t CompositingReasonLayerForMask                           = UINT64_C(1) << 45;
-const uint64_t CompositingReasonLayerForClippingMask                   = UINT64_C(1) << 46;
-const uint64_t CompositingReasonLayerForScrollingBlockSelection        = UINT64_C(1) << 47;
+const uint64_t CompositingReasonLayerForAncestorClip                     = UINT64_C(1) << 39;
+const uint64_t CompositingReasonLayerForDescendantClip                   = UINT64_C(1) << 40;
+const uint64_t CompositingReasonLayerForPerspective                      = UINT64_C(1) << 41;
+const uint64_t CompositingReasonLayerForHorizontalScrollbar              = UINT64_C(1) << 42;
+const uint64_t CompositingReasonLayerForVerticalScrollbar                = UINT64_C(1) << 43;
+const uint64_t CompositingReasonLayerForScrollCorner                     = UINT64_C(1) << 44;
+const uint64_t CompositingReasonLayerForScrollingContents                = UINT64_C(1) << 45;
+const uint64_t CompositingReasonLayerForScrollingContainer               = UINT64_C(1) << 46;
+const uint64_t CompositingReasonLayerForSquashingContents                = UINT64_C(1) << 47;
+const uint64_t CompositingReasonLayerForSquashingContainer               = UINT64_C(1) << 48;
+const uint64_t CompositingReasonLayerForForeground                       = UINT64_C(1) << 49;
+const uint64_t CompositingReasonLayerForBackground                       = UINT64_C(1) << 50;
+const uint64_t CompositingReasonLayerForMask                             = UINT64_C(1) << 51;
+const uint64_t CompositingReasonLayerForClippingMask                     = UINT64_C(1) << 52;
+const uint64_t CompositingReasonLayerForScrollingBlockSelection          = UINT64_C(1) << 53;
 
 // Various combinations of compositing reasons are defined here also, for more intutive and faster bitwise logic.
 const uint64_t CompositingReasonComboAllDirectReasons =
@@ -103,7 +109,15 @@ const uint64_t CompositingReasonComboReasonsThatRequireOwnBacking =
     | CompositingReasonOverlap
     | CompositingReasonAssumedOverlap
     | CompositingReasonNegativeZIndexChildren
-    | CompositingReasonNoSquashingTargetFound
+    | CompositingReasonScrollsWithRespectToSquashingLayer
+    | CompositingReasonSquashingSparsityExceeded
+    | CompositingReasonSquashingClippingContainerMismatch
+    | CompositingReasonSquashingOpacityAncestorMismatch
+    | CompositingReasonSquashingTransformAncestorMismatch
+    | CompositingReasonSquashingFilterAncestorMismatch
+    | CompositingReasonSquashingWouldBreakPaintOrder
+    | CompositingReasonSquashingVideoIsDisallowed
+    | CompositingReasonSquashedLayerClipsCompositingDescendants
     | CompositingReasonTransformWithCompositedDescendants
     | CompositingReasonOpacityWithCompositedDescendants
     | CompositingReasonMaskWithCompositedDescendants
@@ -199,9 +213,33 @@ static const CompositingReasonStringMap compositingReasonStringMap[] = {
     { CompositingReasonNegativeZIndexChildren,
         "negativeZIndexChildren",
         "Parent with composited negative z-index content" },
-    {  CompositingReasonNoSquashingTargetFound,
-        "noSquashingTargetFound",
-        "Cannot be squashed due to no compatible squashing owner found" },
+    { CompositingReasonScrollsWithRespectToSquashingLayer,
+        "scrollsWithRespectToSquashingLayer",
+        "Cannot be squashed since this layer scrolls with respect to the squashing layer" },
+    { CompositingReasonSquashingSparsityExceeded,
+        "squashingSparsityExceeded",
+        "Cannot be squashed as the squashing layer would become too sparse" },
+    { CompositingReasonSquashingClippingContainerMismatch,
+        "squashingClippingContainerMismatch",
+        "Cannot be squashed because this layer has a different clipping container than the squashing layer" },
+    { CompositingReasonSquashingOpacityAncestorMismatch,
+        "squashingOpacityAncestorMismatch",
+        "Cannot be squashed because this layer has a different opacity ancestor than the squashing layer" },
+    { CompositingReasonSquashingTransformAncestorMismatch,
+        "squashingTransformAncestorMismatch",
+        "Cannot be squashed because this layer has a different transform ancestor than the squashing layer" },
+    { CompositingReasonSquashingFilterAncestorMismatch,
+        "squashingFilterAncestorMismatch",
+        "Cannot be squashed because this layer has a different filter ancestor than the squashing layer" },
+    { CompositingReasonSquashingWouldBreakPaintOrder,
+        "squashingWouldBreakPaintOrder",
+        "Cannot be squashed without breaking paint order" },
+    { CompositingReasonSquashingVideoIsDisallowed,
+        "squashingVideoIsDisallowed",
+        "Squashing video is not supported" },
+    { CompositingReasonSquashedLayerClipsCompositingDescendants,
+        "squashedLayerClipsCompositingDescendants",
+        "Squashing a layer that clips composited descendants is not supported." },
     { CompositingReasonTransformWithCompositedDescendants,
         "transformWithCompositedDescendants",
         "Has a transform that needs to be known by compositor because of composited descendants" },