[Fabric] Implement snapToInterval property for ScrollView

[anupriya13]

Description

Type of Change

• New feature (non-breaking change which adds functionality)

Why

Implement snapToInterval property for ScrollView in Fabric

Resolves #13150

What

https://reactnative.dev/docs/scrollview#snaptointerval

The snapToInterval property was available in the Paper implementation via ScrollViewManager.cpp but was missing from the Fabric implementation in ScrollViewComponentView.cpp. This meant that developers using the new architecture couldn't use interval-based snapping behavior.

Solution

Added comprehensive support for snapToInterval that:

1. Detects property changes: Modified updateProps() to check for snapToInterval changes alongside existing snap properties
2. Generates snap points: Created updateSnapPoints() helper method that converts interval values to discrete snap point offsets
3. Handles content changes: Modified updateContentVisualSize() to recalculate snap points when content size changes
4. Respects priority: Follows React Native behavior where snapToOffsets takes priority over snapToInterval

Implementation Details

// Property priority (matches React Native behavior)
if (viewProps.snapToOffsets.size() > 0) {
  // Use explicit snapToOffsets
} else if (viewProps.snapToInterval > 0) {
  // Generate snap points at regular intervals
  float interval = viewProps.snapToInterval * pointScaleFactor;
  for (float offset = 0; offset <= contentLength; offset += interval) {
    snapToOffsets.Append(offset);
  }
}

Testing

Playground tested

Changelog

Should this change be included in the release notes: yes

Add a brief summary of the change to use in the release notes for the next release.
Implement snapToInterval property for ScrollView in Fabric

Microsoft Reviewers: Open in CodeFlow