Always composite position: fixed elements with composited descendants.

third_party/WebKit/Source/platform/graphics/CompositingReasons.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CompositingReasons_h
 #define CompositingReasons_h
 
 #include "platform/PlatformExport.h"
 #include "wtf/MathExtras.h"
 #include <stdint.h>
@@ skipping 44 matching lines @@
 const uint64_t CompositingReasonOpacityWithCompositedDescendants         = UINT64_C(1) << 33;
 const uint64_t CompositingReasonMaskWithCompositedDescendants            = UINT64_C(1) << 34;
 const uint64_t CompositingReasonReflectionWithCompositedDescendants      = UINT64_C(1) << 35;
 const uint64_t CompositingReasonFilterWithCompositedDescendants          = UINT64_C(1) << 36;
 const uint64_t CompositingReasonBlendingWithCompositedDescendants        = UINT64_C(1) << 37;
 const uint64_t CompositingReasonClipsCompositingDescendants              = UINT64_C(1) << 38;
 const uint64_t CompositingReasonPerspectiveWith3DDescendants             = UINT64_C(1) << 39;
 const uint64_t CompositingReasonPreserve3DWith3DDescendants              = UINT64_C(1) << 40;
 const uint64_t CompositingReasonReflectionOfCompositedParent             = UINT64_C(1) << 41;
 const uint64_t CompositingReasonIsolateCompositedDescendants             = UINT64_C(1) << 42;
+const uint64_t CompositingReasonPositionFixedWithCompositedDescendants   = UINT64_C(1) << 43;
 
 // 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) << 43;
+const uint64_t CompositingReasonRoot                                     = UINT64_C(1) << 44;
 
 // CompositedLayerMapping internal hierarchy reasons
-const uint64_t CompositingReasonLayerForAncestorClip                     = UINT64_C(1) << 44;
-const uint64_t CompositingReasonLayerForDescendantClip                   = UINT64_C(1) << 45;
-const uint64_t CompositingReasonLayerForPerspective                      = UINT64_C(1) << 46;
-const uint64_t CompositingReasonLayerForHorizontalScrollbar              = UINT64_C(1) << 47;
-const uint64_t CompositingReasonLayerForVerticalScrollbar                = UINT64_C(1) << 48;
-const uint64_t CompositingReasonLayerForOverflowControlsHost             = UINT64_C(1) << 49;
-const uint64_t CompositingReasonLayerForScrollCorner                     = UINT64_C(1) << 50;
-const uint64_t CompositingReasonLayerForScrollingContents                = UINT64_C(1) << 51;
-const uint64_t CompositingReasonLayerForScrollingContainer               = UINT64_C(1) << 52;
-const uint64_t CompositingReasonLayerForSquashingContents                = UINT64_C(1) << 53;
-const uint64_t CompositingReasonLayerForSquashingContainer               = UINT64_C(1) << 54;
-const uint64_t CompositingReasonLayerForForeground                       = UINT64_C(1) << 55;
-const uint64_t CompositingReasonLayerForBackground                       = UINT64_C(1) << 56;
-const uint64_t CompositingReasonLayerForMask                             = UINT64_C(1) << 57;
-const uint64_t CompositingReasonLayerForClippingMask                     = UINT64_C(1) << 58;
-const uint64_t CompositingReasonLayerForScrollingBlockSelection          = UINT64_C(1) << 59;
+const uint64_t CompositingReasonLayerForAncestorClip                     = UINT64_C(1) << 45;
+const uint64_t CompositingReasonLayerForDescendantClip                   = UINT64_C(1) << 46;
+const uint64_t CompositingReasonLayerForPerspective                      = UINT64_C(1) << 47;
+const uint64_t CompositingReasonLayerForHorizontalScrollbar              = UINT64_C(1) << 48;
+const uint64_t CompositingReasonLayerForVerticalScrollbar                = UINT64_C(1) << 49;
+const uint64_t CompositingReasonLayerForOverflowControlsHost             = UINT64_C(1) << 50;
+const uint64_t CompositingReasonLayerForScrollCorner                     = UINT64_C(1) << 51;
+const uint64_t CompositingReasonLayerForScrollingContents                = UINT64_C(1) << 52;
+const uint64_t CompositingReasonLayerForScrollingContainer               = UINT64_C(1) << 53;
+const uint64_t CompositingReasonLayerForSquashingContents                = UINT64_C(1) << 54;
+const uint64_t CompositingReasonLayerForSquashingContainer               = UINT64_C(1) << 55;
+const uint64_t CompositingReasonLayerForForeground                       = UINT64_C(1) << 56;
+const uint64_t CompositingReasonLayerForBackground                       = UINT64_C(1) << 57;
+const uint64_t CompositingReasonLayerForMask                             = UINT64_C(1) << 58;
+const uint64_t CompositingReasonLayerForClippingMask                     = UINT64_C(1) << 59;
+const uint64_t CompositingReasonLayerForScrollingBlockSelection          = UINT64_C(1) << 60;
 
 // Composited elements with inline transforms trigger assumed overlap so that
 // we can update their transforms quickly.
-const uint64_t CompositingReasonInlineTransform                          = UINT64_C(1) << 60;
+const uint64_t CompositingReasonInlineTransform                          = UINT64_C(1) << 61;
 
-const uint64_t CompositingReasonCompositorProxy                          = UINT64_C(1) << 61;
+const uint64_t CompositingReasonCompositorProxy                          = UINT64_C(1) << 62;
 
 // Various combinations of compositing reasons are defined here also, for more intutive and faster bitwise logic.
 const uint64_t CompositingReasonComboAllDirectReasons =
     CompositingReason3DTransform
     | CompositingReasonVideo
     | CompositingReasonCanvas
     | CompositingReasonPlugin
     | CompositingReasonIFrame
     | CompositingReasonBackfaceVisibilityHidden
     | CompositingReasonActiveAnimation
@@ skipping 17 matching lines @@
     | CompositingReasonBackdropFilter;
 
 const uint64_t CompositingReasonComboCompositedDescendants =
     CompositingReasonTransformWithCompositedDescendants
     | CompositingReasonIsolateCompositedDescendants
     | CompositingReasonOpacityWithCompositedDescendants
     | CompositingReasonMaskWithCompositedDescendants
     | CompositingReasonFilterWithCompositedDescendants
     | CompositingReasonBlendingWithCompositedDescendants
     | CompositingReasonReflectionWithCompositedDescendants
-    | CompositingReasonClipsCompositingDescendants;
+    | CompositingReasonClipsCompositingDescendants
+    | CompositingReasonPositionFixedWithCompositedDescendants;
 
 const uint64_t CompositingReasonCombo3DDescendants =
     CompositingReasonPreserve3DWith3DDescendants
     | CompositingReasonPerspectiveWith3DDescendants;
 
 const uint64_t CompositingReasonComboAllStyleDeterminedReasons =
     CompositingReasonComboAllDirectStyleDeterminedReasons
     | CompositingReasonComboCompositedDescendants
     | CompositingReasonCombo3DDescendants
     | CompositingReasonInlineTransform;
@@ skipping 17 matching lines @@
     | CompositingReasonSquashingBlendingIsDisallowed
     | CompositingReasonTransformWithCompositedDescendants
     | CompositingReasonOpacityWithCompositedDescendants
     | CompositingReasonMaskWithCompositedDescendants
     | CompositingReasonFilterWithCompositedDescendants
     | CompositingReasonBlendingWithCompositedDescendants
     | CompositingReasonIsolateCompositedDescendants
     | CompositingReasonPreserve3DWith3DDescendants // preserve-3d has to create backing store to ensure that 3d-transformed elements intersect.
     | CompositingReasonSquashingNearestFixedPositionMismatch
     | CompositingReasonScrollChildWithCompositedDescendants
-    | CompositingReasonBackdropFilter;
+    | CompositingReasonBackdropFilter
+    | CompositingReasonPositionFixedWithCompositedDescendants;
 
 const uint64_t CompositingReasonComboSquashableReasons =
     CompositingReasonOverlap
     | CompositingReasonAssumedOverlap
     | CompositingReasonOverflowScrollingParent;
 
 typedef uint64_t CompositingReasons;
 
 // Any reasons other than overlap or assumed overlap will require the layer to be separately compositing.
 inline bool requiresCompositing(CompositingReasons reasons)
@@ skipping 12 matching lines @@
     const char* shortName;
     const char* description;
 };
 
 PLATFORM_EXPORT extern const CompositingReasonStringMap kCompositingReasonStringMap[];
 PLATFORM_EXPORT extern size_t kNumberOfCompositingReasons;
 
 } // namespace blink
 
 #endif // CompositingReasons_h