chore: scrollToIndex and scrollToOffset adjustments

android/src/main/java/com/shadowlist/SLContainer.java

@@ -235,4 +235,20 @@ public void run() {
       }
     }, 16);
   }
+
+  public void scrollToIndex(int index, boolean animated) {
+    MapBuffer stateMapBuffer = mStateWrapper.getStateDataMapBuffer();
+    int headerFooter = 1;
+    int offset = mChildrenMeasurements.adjustVisibleStartIndex(
+      (int) mChildrenMeasurements.sum(index + headerFooter),
+      stateMapBuffer.getInt(SLContainerManager.SLCONTAINER_STATE_CHILDREN_MEASUREMENTS_TREE_SIZE)
+    );
+    float[] scrollPosition = mScrollable.getScrollPositionFromOffset(offset);
+    mScrollContainerVertical.scrollTo((int)PixelUtil.toPixelFromDIP(scrollPosition[0]), (int)PixelUtil.toPixelFromDIP(scrollPosition[1]));
+  }
+
+  public void scrollToOffset(int offset, boolean animated) {
+    float[] scrollPosition = mScrollable.getScrollPositionFromOffset(offset);
+    mScrollContainerVertical.scrollTo((int)PixelUtil.toPixelFromDIP(scrollPosition[0]), (int)PixelUtil.toPixelFromDIP(scrollPosition[1]));
+  }
 }

android/src/main/java/com/shadowlist/SLContainerManager.java

@@ -180,12 +180,12 @@ public void receiveCommand(@NonNull SLContainer view, String commandId, @Nullabl
 
   @Override
   public void scrollToIndex(SLContainer view, int index, boolean animated) {
-
+    view.scrollToIndex(index, animated);
   }
 
   @Override
   public void scrollToOffset(SLContainer view, int offset, boolean animated) {
-
+    view.scrollToOffset(offset, animated);
   }
 
   public static final String NAME = "SLContainer";

android/src/main/java/com/shadowlist/SLScrollable.java

@@ -126,4 +126,8 @@ public float getVisibleStartOffset(float[] scrollPosition) {
   public float getVisibleEndOffset(float[] scrollPosition) {
     return getScrollPosition(scrollPosition) + mScrollContainerHeight;
   }
+
+  public float[] getScrollPositionFromOffset(float scrollOffset) {
+    return mHorizontal ? new float[]{scrollOffset, 0} : new float[]{0, scrollOffset};
+  }
 }

example/src/App.tsx

@@ -1,4 +1,4 @@
-import { useRef, useCallback } from 'react';
+import { useRef, useCallback, useEffect } from 'react';
 import { SafeAreaView, StyleSheet, Text, View } from 'react-native';
 import type { DirectEventHandler } from 'react-native/Libraries/Types/CodegenTypes';
 import {
@@ -16,6 +16,7 @@ const ITEMS_COUNT = 50;
 const IS_INVERTED = false;
 const IS_HORIZONTAL = false;
 const INITIAL_SCROLL_INDEX = 0;
+const FINAL_SCROLL_INDEX = 0;
 
 const ListHeaderComponent = () => (
   <View style={styles.static}>
@@ -43,6 +44,13 @@ export default function App() {
   const data = useData({ length: ITEMS_COUNT, inverted: IS_INVERTED });
   const ref = useRef<SLContainerRef>(null);
 
+  useEffect(() => {
+    if (!FINAL_SCROLL_INDEX) return;
+    setTimeout(() => {
+      ref.current?.scrollToIndex({ index: FINAL_SCROLL_INDEX });
+    }, 1000);
+  }, []);
+
   const onStartReached = useCallback<DirectEventHandler<OnStartReached>>(
     (event) => {
       !IS_INVERTED ? data.loadPrepend() : data.loadAppend();

ios/SLContainer.mm

@@ -175,18 +175,18 @@ - (void)handleCommand:(const NSString *)commandName args:(const NSArray *)args
 - (void)scrollToIndexNativeCommand:(int)index animated:(BOOL)animated
 {
   auto headerFooter = 1;
-  auto stateData = _state->getData();
-  stateData.scrollPosition = stateData.calculateScrollPositionOffset(
-    stateData.childrenMeasurementsTree.sum(index + headerFooter)
+  auto nextStateData = self->_state->getData();
+  auto offset = adjustVisibleStartIndex(
+    nextStateData.childrenMeasurementsTree.sum(index + headerFooter),
+    nextStateData.childrenMeasurementsTree.size()
   );
-  self->_state->updateState(std::move(stateData));
+
+  [self->_scrollContent setContentOffset:[self->_scrollable getScrollPositionFromOffset:offset] animated:animated];
 }
 
 - (void)scrollToOffsetNativeCommand:(int)offset animated:(BOOL)animated
 {
-  auto stateData = _state->getData();
-  stateData.scrollPosition = stateData.calculateScrollPositionOffset(offset);
-  self->_state->updateState(std::move(stateData));
+  [self->_scrollContent setContentOffset:[self->_scrollable getScrollPositionFromOffset:offset] animated:animated];
 }
 
 - (void)handleRefresh {

ios/SLScrollable.h

@@ -22,5 +22,6 @@
 - (float)getScrollPosition:(CGPoint)scrollPosition;
 - (float)getVisibleStartOffset:(CGPoint)scrollPosition;
 - (float)getVisibleEndOffset:(CGPoint)scrollPosition;
+- (CGPoint)getScrollPositionFromOffset:(float)scrollOffset;
 
 @end

ios/SLScrollable.mm

@@ -124,4 +124,7 @@ - (float)getVisibleEndOffset:(CGPoint)scrollPosition {
   return [self getScrollPosition:scrollPosition] + self->_scrollContainerHeight;
 }
 
+- (CGPoint)getScrollPositionFromOffset:(float)scrollOffset {
+  return self->_horizontal ? CGPointMake(scrollOffset, 0) : CGPointMake(0, scrollOffset);
+}
 @end