scrollview: add option to tag event while drawing (#128)

Author: hannojg

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/shell/MainReactPackage.kt

@@ -139,7 +139,7 @@ constructor(private val config: MainPackageConfig? = null) :
           ReactHorizontalScrollViewManager(),
           ReactHorizontalScrollContainerViewManager(),
           ReactProgressBarViewManager(),
-          ReactScrollViewManager(),
+          // ReactScrollViewManager(),
           ReactSwitchManager(),
           ReactSafeAreaViewManager(),
           SwipeRefreshLayoutManager(),
@@ -172,8 +172,8 @@ constructor(private val config: MainPackageConfig? = null) :
               ModuleSpec.viewManagerSpec { ReactProgressBarViewManager() },
           ReactSafeAreaViewManager.REACT_CLASS to
               ModuleSpec.viewManagerSpec { ReactSafeAreaViewManager() },
-          ReactScrollViewManager.REACT_CLASS to
-              ModuleSpec.viewManagerSpec { ReactScrollViewManager() },
+          // ReactScrollViewManager.REACT_CLASS to
+          //     ModuleSpec.viewManagerSpec { ReactScrollViewManager() },
           ReactSwitchManager.REACT_CLASS to ModuleSpec.viewManagerSpec { ReactSwitchManager() },
           SwipeRefreshLayoutManager.REACT_CLASS to
               ModuleSpec.viewManagerSpec { SwipeRefreshLayoutManager() },

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/uimanager/events/Event.kt

@@ -40,6 +40,9 @@ public abstract class Event<T : Event<T>> {
   public var viewTag: Int = 0
     private set
 
+  /** @return whether this event is dispatched during a drawing pass */
+  public var isDrawing: Boolean = false
+
   /**
    * @return the time at which the event happened in the [android.os.SystemClock.uptimeMillis] base.
    */

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/views/scroll/ReactScrollView.java

@@ -463,24 +463,29 @@ private void scrollToChild(View child) {
 
   @Override
   protected void onScrollChanged(int x, int y, int oldX, int oldY) {
-    Systrace.beginSection(Systrace.TRACE_TAG_REACT, "ReactScrollView.onScrollChanged");
-    try {
-      super.onScrollChanged(x, y, oldX, oldY);
+    onScrollChanged(x, y, oldX, oldY, false);
+  }
 
-      mActivelyScrolling = true;
+  protected void onScrollChanged(int x, int y, int oldX, int oldY, boolean isDrawing) {
+      Systrace.beginSection(Systrace.TRACE_TAG_REACT, "ReactScrollView.onScrollChanged");
+      try {
+          super.onScrollChanged(x, y, oldX, oldY);
 
-      if (mOnScrollDispatchHelper.onScrollChanged(x, y)) {
-        if (mRemoveClippedSubviews) {
-          updateClippingRect();
-        }
-        ReactScrollViewHelper.updateStateOnScrollChanged(
-            this,
-            mOnScrollDispatchHelper.getXFlingVelocity(),
-            mOnScrollDispatchHelper.getYFlingVelocity());
+          mActivelyScrolling = true;
+
+          if (mOnScrollDispatchHelper.onScrollChanged(x, y)) {
+              if (mRemoveClippedSubviews) {
+                  updateClippingRect();
+              }
+              ReactScrollViewHelper.updateStateOnScrollChanged(
+                      this,
+                      mOnScrollDispatchHelper.getXFlingVelocity(),
+                      mOnScrollDispatchHelper.getYFlingVelocity(),
+                      isDrawing);
+          }
+      } finally {
+          Systrace.endSection(Systrace.TRACE_TAG_REACT);
       }
-    } finally {
-      Systrace.endSection(Systrace.TRACE_TAG_REACT);
-    }
   }
 
   @Override

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/views/scroll/ReactScrollViewHelper.kt

@@ -65,10 +65,10 @@ public object ReactScrollViewHelper {
 
   /** Shared by [ReactScrollView] and [ReactHorizontalScrollView]. */
   @JvmStatic
-  public fun <T> emitScrollEvent(scrollView: T, xVelocity: Float, yVelocity: Float) where
+  public fun <T> emitScrollEvent(scrollView: T, xVelocity: Float, yVelocity: Float, isDrawing: Boolean = false) where
   T : HasScrollEventThrottle?,
   T : ViewGroup {
-    emitScrollEvent(scrollView, ScrollEventType.SCROLL, xVelocity, yVelocity)
+    emitScrollEvent(scrollView, ScrollEventType.SCROLL, xVelocity, yVelocity, isDrawing)
   }
 
   @JvmStatic
@@ -111,6 +111,7 @@ public object ReactScrollViewHelper {
       scrollEventType: ScrollEventType,
       xVelocity: Float,
       yVelocity: Float,
+      isDrawing: Boolean = false
   ) where T : HasScrollEventThrottle?, T : ViewGroup {
     val now = System.currentTimeMillis()
     // Throttle the scroll event if scrollEventThrottle is set to be equal or more than 17 ms.
@@ -146,7 +147,9 @@ public object ReactScrollViewHelper {
               contentView.width,
               contentView.height,
               scrollView.width,
-              scrollView.height))
+              scrollView.height).also {
+                  it.isDrawing = isDrawing
+          })
       if (scrollEventType == ScrollEventType.SCROLL) {
         scrollView.lastScrollDispatchTime = now
       }
@@ -368,7 +371,8 @@ public object ReactScrollViewHelper {
   public fun <T> updateStateOnScrollChanged(
       scrollView: T,
       xVelocity: Float,
-      yVelocity: Float
+      yVelocity: Float,
+      isDrawing: Boolean = false
   ) where
   T : HasFlingAnimator?,
   T : HasScrollEventThrottle?,
@@ -380,7 +384,7 @@ public object ReactScrollViewHelper {
     // "more correct" scroll position. It will frequently be /incorrect/ but this decreases
     // the error as much as possible.
     updateFabricScrollState(scrollView, scrollView.scrollX, scrollView.scrollY)
-    emitScrollEvent(scrollView, xVelocity, yVelocity)
+    emitScrollEvent(scrollView, xVelocity, yVelocity, isDrawing)
   }
 
   public fun <T> registerFlingAnimator(scrollView: T) where