Add Visibility flag for hiding/unhiding trees (facebook#20043)

* Add Visibility flag for hiding/unhiding trees

There's `beforeblur` logic in the snapshot phase that needs to visit
every Suspense boundary whose visibility is toggled. Right now it does
that by visiting Placement and Deletion effects. That includes many
unrelated nodes.

By adding a new flag specifically for toggling Visibility, we will only
visit the relevant Suspense (and Offscreen) boundaries, instead of all
nodes that have a Placement.

Potential follow-ups (not urgent):

- The `beforeblur` logic also has a check to see whether the visibility
was toggled on or off. It only cares about things being hidden. As a
follow up, I can split the Visibility flag into separate Hide/Show
flags, and only visit Hide.
- Now that this is separate from Update, we can move the rest of the
Suspense's layout effects (like attaching retry listeners) to the
passive phase.

* Gate behind createEventHandle feature flag

Only need to visit deleted and hidden trees during the snapshot phase
if the experimental `createEventHandle` flag is enabled. Currently,
it's only used internally at Facebook, not open source.

packages/react-reconciler/src/ReactFiberCompleteWork.new.js

@@ -73,6 +73,7 @@ import {
   NoFlags,
   DidCapture,
   Snapshot,
+  Visibility,
   MutationMask,
   LayoutMask,
   PassiveMask,
@@ -1154,8 +1155,8 @@ function completeWork(
         // TODO: Only schedule updates if not prevDidTimeout.
         if (nextDidTimeout) {
           // If this boundary just timed out, schedule an effect to attach a
-          // retry listener to the promise. This flag is also used to hide the
-          // primary children.
+          // retry listener to the promise.
+          // TODO: Move to passive phase
           workInProgress.flags |= Update;
         }
       }
@@ -1167,7 +1168,7 @@ function completeWork(
           // primary children. In mutation mode, we also need the flag to
           // *unhide* children that were previously hidden, so check if this
           // is currently timed out, too.
-          workInProgress.flags |= Update;
+          workInProgress.flags |= Update | Visibility;
         }
       }
       if (
@@ -1176,6 +1177,7 @@ function completeWork(
         workInProgress.memoizedProps.suspenseCallback != null
       ) {
         // Always notify the callback
+        // TODO: Move to passive phase
         workInProgress.flags |= Update;
       }
       bubbleProperties(workInProgress);
@@ -1523,7 +1525,7 @@ function completeWork(
           prevIsHidden !== nextIsHidden &&
           newProps.mode !== 'unstable-defer-without-hiding'
         ) {
-          workInProgress.flags |= Update;
+          workInProgress.flags |= Update | Visibility;
         }
       }
 

packages/react-reconciler/src/ReactFiberFlags.js

@@ -7,62 +7,72 @@
  * @flow
  */
 
+import {enableCreateEventHandleAPI} from 'shared/ReactFeatureFlags';
+
 export type Flags = number;
 
 // Don't change these two values. They're used by React Dev Tools.
-export const NoFlags = /*                      */ 0b000000000000000000;
-export const PerformedWork = /*                */ 0b000000000000000001;
+export const NoFlags = /*                      */ 0b0000000000000000000;
+export const PerformedWork = /*                */ 0b0000000000000000001;
 
 // You can change the rest (and add more).
-export const Placement = /*                    */ 0b000000000000000010;
-export const Update = /*                       */ 0b000000000000000100;
-export const PlacementAndUpdate = /*           */ 0b000000000000000110;
-export const Deletion = /*                     */ 0b000000000000001000;
-export const ContentReset = /*                 */ 0b000000000000010000;
-export const Callback = /*                     */ 0b000000000000100000;
-export const DidCapture = /*                   */ 0b000000000001000000;
-export const Ref = /*                          */ 0b000000000010000000;
-export const Snapshot = /*                     */ 0b000000000100000000;
-export const Passive = /*                      */ 0b000000001000000000;
-// TODO (effects) Remove this bit once the new reconciler is synced to the old.
-export const PassiveUnmountPendingDev = /*     */ 0b000010000000000000;
-export const Hydrating = /*                    */ 0b000000010000000000;
-export const HydratingAndUpdate = /*           */ 0b000000010000000100;
+export const Placement = /*                    */ 0b0000000000000000010;
+export const Update = /*                       */ 0b0000000000000000100;
+export const PlacementAndUpdate = /*           */ 0b0000000000000000110;
+export const Deletion = /*                     */ 0b0000000000000001000;
+export const ContentReset = /*                 */ 0b0000000000000010000;
+export const Callback = /*                     */ 0b0000000000000100000;
+export const DidCapture = /*                   */ 0b0000000000001000000;
+export const Ref = /*                          */ 0b0000000000010000000;
+export const Snapshot = /*                     */ 0b0000000000100000000;
+export const Passive = /*                      */ 0b0000000001000000000;
+export const Hydrating = /*                    */ 0b0000000010000000000;
+export const HydratingAndUpdate = /*           */ 0b0000000010000000100;
+export const Visibility = /*                   */ 0b0000000100000000000;
 
 // Passive & Update & Callback & Ref & Snapshot
-export const LifecycleEffectMask = /*          */ 0b000000001110100100;
+export const LifecycleEffectMask = /*          */ 0b0000000001110100100;
 
 // Union of all host effects
-export const HostEffectMask = /*               */ 0b000000011111111111;
+export const HostEffectMask = /*               */ 0b0000000111111111111;
 
 // These are not really side effects, but we still reuse this field.
-export const Incomplete = /*                   */ 0b000000100000000000;
-export const ShouldCapture = /*                */ 0b000001000000000000;
-export const ForceUpdateForLegacySuspense = /* */ 0b000100000000000000;
+export const Incomplete = /*                   */ 0b0000001000000000000;
+export const ShouldCapture = /*                */ 0b0000010000000000000;
+// TODO (effects) Remove this bit once the new reconciler is synced to the old.
+export const PassiveUnmountPendingDev = /*     */ 0b0000100000000000000;
+export const ForceUpdateForLegacySuspense = /* */ 0b0001000000000000000;
 
 // Static tags describe aspects of a fiber that are not specific to a render,
 // e.g. a fiber uses a passive effect (even if there are no updates on this particular render).
 // This enables us to defer more work in the unmount case,
 // since we can defer traversing the tree during layout to look for Passive effects,
 // and instead rely on the static flag as a signal that there may be cleanup work.
-export const PassiveStatic = /*                */ 0b001000000000000000;
+export const PassiveStatic = /*                */ 0b0010000000000000000;
 
 // Union of side effect groupings as pertains to subtreeFlags
-// TODO: Don't need to visit Placement during BeforeMutation phase
-// TODO: Only need to visit Deletions during BeforeMutation phase if an element
-// is focused.
-export const BeforeMutationMask = /*           */ 0b000000000100001010;
-export const MutationMask = /*                 */ 0b000000010010011110;
-export const LayoutMask = /*                   */ 0b000000000010100100;
-export const PassiveMask = /*                  */ 0b000000001000001000;
+
+export const BeforeMutationMask =
+  Snapshot |
+  (enableCreateEventHandleAPI
+    ? // createEventHandle needs to visit deleted and hidden trees to
+      // fire beforeblur
+      // TODO: Only need to visit Deletions during BeforeMutation phase if an
+      // element is focused.
+      Deletion | Visibility
+    : 0);
+
+export const MutationMask = /*                 */ 0b0000000110010011110;
+export const LayoutMask = /*                   */ 0b0000000000010100100;
+export const PassiveMask = /*                  */ 0b0000000001000001000;
 
 // Union of tags that don't get reset on clones.
 // This allows certain concepts to persist without recalculting them,
 // e.g. whether a subtree contains passive effects or portals.
-export const StaticMask = /*                   */ 0b001000000000000000;
+export const StaticMask = /*                   */ 0b0010000000000000000;
 
 // These flags allow us to traverse to fibers that have effects on mount
 // without traversing the entire tree after every commit for
 // double invoking
-export const MountLayoutDev = /*               */ 0b010000000000000000;
-export const MountPassiveDev = /*              */ 0b100000000000000000;
+export const MountLayoutDev = /*               */ 0b0100000000000000000;
+export const MountPassiveDev = /*              */ 0b1000000000000000000;

packages/react-reconciler/src/ReactFiberWorkLoop.new.js

@@ -134,6 +134,7 @@ import {
   HostEffectMask,
   Hydrating,
   HydratingAndUpdate,
+  Visibility,
   BeforeMutationMask,
   MutationMask,
   LayoutMask,
@@ -2155,8 +2156,10 @@ function commitBeforeMutationEffectsImpl(fiber: Fiber) {
 
   if (!shouldFireAfterActiveInstanceBlur && focusedInstanceHandle !== null) {
     // Check to see if the focused element was inside of a hidden (Suspense) subtree.
-    // TODO: Move this out of the hot path using a dedicated effect tag.
     if (
+      // TODO: Can optimize this further with separate Hide and Show flags. We
+      // only care about Hide here.
+      (flags & Visibility) !== NoFlags &&
       fiber.tag === SuspenseComponent &&
       isSuspenseBoundaryBeingHidden(current, fiber) &&
       doesFiberContain(fiber, focusedInstanceHandle)