Add basic active pointer tracking to the pointer event processor (#38865

)

Summary:
Pull Request resolved: #38865

Changelog: [Internal] - Add basic active pointer tracking to the pointer event processor

This diff lays the groundwork for keeping track of all the "active" pointers. The ActivePointer struct right now only contains a copy of the PointerEvent data but in future diffs this will be extended to include additional stateful metadata.

It's important to note that the code as written in this diff only "tracks" pointers when they are down and won't track pointers that are only hovering. I do want to include this in future diffs but I couldn't include that handling here as it requires changes to the iOS native pointer handling to stop deriving its own hover events which ends up snowballing even more changes. I will be making this change in (hopefully) the next diff where I refactor the hover event derivation to the fabric C++ layer.

Reviewed By: rozele

Differential Revision: D48167438

fbshipit-source-id: d1c7146e7b8d46b2f8defd4785618ee1cd54f155

packages/react-native/ReactCommon/react/renderer/uimanager/PointerEventsProcessor.cpp

@@ -222,6 +222,16 @@ void PointerEventsProcessor::interceptPointerEvent(
     eventTarget = retargeted.target.get();
   }
 
+  if (type == "topPointerDown") {
+    registerActivePointer(pointerEvent);
+  } else if (type == "topPointerMove") {
+    // TODO: Remove the need for this check by properly handling
+    // pointerenter/pointerleave events emitted from the native platform
+    if (getActivePointer(pointerEvent.pointerId) != nullptr) {
+      updateActivePointer(pointerEvent);
+    }
+  }
+
   eventTarget->retain(runtime);
   auto shadowNode = getShadowNodeFromEventTarget(runtime, *eventTarget);
   if (shadowNode != nullptr &&
@@ -237,30 +247,45 @@ void PointerEventsProcessor::interceptPointerEvent(
     processPendingPointerCapture(
         pointerEvent, runtime, eventDispatcher, uiManager);
   }
+
+  if (type == "topPointerUp" || type == "topPointerCancel") {
+    unregisterActivePointer(pointerEvent);
+  }
 }
 
 void PointerEventsProcessor::setPointerCapture(
     PointerIdentifier pointerId,
     ShadowNode::Shared const &shadowNode) {
-  // TODO: Throw DOMException with name "NotFoundError" when pointerId does not
-  // match any of the active pointers
-  pendingPointerCaptureTargetOverrides_[pointerId] = shadowNode;
+  if (auto activePointer = getActivePointer(pointerId)) {
+    // As per the spec this method should silently fail if the pointer in
+    // question does not have any active buttons
+    if (activePointer->event.buttons == 0) {
+      return;
+    }
+
+    pendingPointerCaptureTargetOverrides_[pointerId] = shadowNode;
+  } else {
+    // TODO: Throw DOMException with name "NotFoundError" when pointerId does
+    // not match any of the active pointers
+  }
 }
 
 void PointerEventsProcessor::releasePointerCapture(
     PointerIdentifier pointerId,
     ShadowNode const *shadowNode) {
-  // TODO: Throw DOMException with name "NotFoundError" when pointerId does not
-  // match any of the active pointers
-
-  // We only clear the pointer's capture target override if release was called
-  // on the shadowNode which has the capture override, otherwise the result
-  // should no-op
-  auto pendingTarget = getCaptureTargetOverride(
-      pointerId, pendingPointerCaptureTargetOverrides_);
-  if (pendingTarget != nullptr &&
-      pendingTarget->getTag() == shadowNode->getTag()) {
-    pendingPointerCaptureTargetOverrides_.erase(pointerId);
+  if (getActivePointer(pointerId) != nullptr) {
+    // We only clear the pointer's capture target override if release was called
+    // on the shadowNode which has the capture override, otherwise the result
+    // should no-op
+    auto pendingTarget = getCaptureTargetOverride(
+        pointerId, pendingPointerCaptureTargetOverrides_);
+    if (pendingTarget != nullptr &&
+        pendingTarget->getTag() == shadowNode->getTag()) {
+      pendingPointerCaptureTargetOverrides_.erase(pointerId);
+    }
+  } else {
+    // TODO: Throw DOMException with name "NotFoundError" when pointerId does
+    // not match any of the active pointers
   }
 }
 
@@ -275,6 +300,38 @@ bool PointerEventsProcessor::hasPointerCapture(
   return false;
 }
 
+ActivePointer *PointerEventsProcessor::getActivePointer(
+    PointerIdentifier pointerId) {
+  auto it = activePointers_.find(pointerId);
+  return (it == activePointers_.end()) ? nullptr : &it->second;
+}
+
+void PointerEventsProcessor::registerActivePointer(PointerEvent const &event) {
+  ActivePointer activePointer = {};
+  activePointer.event = event;
+
+  activePointers_[event.pointerId] = activePointer;
+}
+
+void PointerEventsProcessor::updateActivePointer(PointerEvent const &event) {
+  if (auto activePointer = getActivePointer(event.pointerId)) {
+    activePointer->event = event;
+  } else {
+    LOG(WARNING)
+        << "Inconsistency between local and platform pointer registries: attempting to update an active pointer which has never been registered.";
+  }
+}
+
+void PointerEventsProcessor::unregisterActivePointer(
+    PointerEvent const &event) {
+  if (getActivePointer(event.pointerId) != nullptr) {
+    activePointers_.erase(event.pointerId);
+  } else {
+    LOG(WARNING)
+        << "Inconsistency between local and platform pointer registries: attempting to unregister an active pointer which has never been registered.";
+  }
+}
+
 void PointerEventsProcessor::processPendingPointerCapture(
     PointerEvent const &event,
     jsi::Runtime &runtime,

packages/react-native/ReactCommon/react/renderer/uimanager/PointerEventsProcessor.h

@@ -15,6 +15,18 @@
 
 namespace facebook::react {
 
+// Helper struct to package a PointerEvent and SharedEventTarget together
+struct PointerEventTarget {
+  PointerEvent event;
+  SharedEventTarget target;
+};
+
+// Helper struct to contain an active pointer's event data along with additional
+// metadata
+struct ActivePointer {
+  PointerEvent event;
+};
+
 using DispatchEvent = std::function<void(
     jsi::Runtime &runtime,
     const EventTarget *eventTarget,
@@ -26,11 +38,8 @@ using PointerIdentifier = int32_t;
 using CaptureTargetOverrideRegistry =
     std::unordered_map<PointerIdentifier, ShadowNode::Weak>;
 
-// Helper struct to package a PointerEvent and SharedEventTarget together
-struct PointerEventTarget {
-  PointerEvent event;
-  SharedEventTarget target;
-};
+using ActivePointerRegistry =
+    std::unordered_map<PointerIdentifier, ActivePointer>;
 
 class PointerEventsProcessor final {
  public:
@@ -54,12 +63,20 @@ class PointerEventsProcessor final {
       ShadowNode const *shadowNode);
 
  private:
+  ActivePointer *getActivePointer(PointerIdentifier pointerId);
+
+  void registerActivePointer(PointerEvent const &event);
+  void updateActivePointer(PointerEvent const &event);
+  void unregisterActivePointer(PointerEvent const &event);
+
   void processPendingPointerCapture(
       PointerEvent const &event,
       jsi::Runtime &runtime,
       DispatchEvent const &eventDispatcher,
       UIManager const &uiManager);
 
+  ActivePointerRegistry activePointers_;
+
   CaptureTargetOverrideRegistry pendingPointerCaptureTargetOverrides_;
   CaptureTargetOverrideRegistry activePointerCaptureTargetOverrides_;
 };