fix(rtl): horizontal RTL initial scroll mispositions on mount (mirror at end, blank at index 0)

src/components/LegendList.tsx

@@ -518,7 +518,14 @@ const LegendListInner = typedForwardRef(function LegendListInner<T>(
         }
 
         const resolvedOffset = initialScroll.contentOffset ?? resolveInitialScrollOffset(ctx, initialScroll);
-        return usesBootstrapInitialScroll && state.initialScrollSession?.kind === "bootstrap" && Platform.OS === "web"
+        // For a horizontal RTL *bootstrap* scroll (initialScrollIndex / initialScrollAtEnd),
+        // this seed is a logical (LTR) offset; feeding it to the native `contentOffset`
+        // unconverted lands on the RTL mirror. Skip the seed and let the bootstrap
+        // dispatch (which converts) position the list. Scoped to bootstrap sessions so
+        // offset-only initial scrolls still apply their offset.
+        return usesBootstrapInitialScroll &&
+            ((state.initialScrollSession?.kind === "bootstrap" && Platform.OS === "web") ||
+                isHorizontalRTLProps({ horizontal, rtl }))
             ? undefined
             : resolvedOffset;
     }, [usesBootstrapInitialScroll]);

src/core/bootstrapInitialScroll.ts

@@ -10,6 +10,7 @@ import { IS_DEV } from "@/utils/devEnvironment";
 import { getId } from "@/utils/getId";
 import { getItemSize } from "@/utils/getItemSize";
 import { requestAdjust } from "@/utils/requestAdjust";
+import { isHorizontalRTL } from "@/utils/rtl";
 
 const DEFAULT_BOOTSTRAP_REVEAL_EPSILON = 1;
 const DEFAULT_BOOTSTRAP_REVEAL_MAX_FRAMES = 8;
@@ -525,6 +526,12 @@ export function startBootstrapInitialScrollOnMount(
     const shouldFinishAtOrigin =
         offset === 0 &&
         !initialScrollAtEnd &&
+        // For a horizontal RTL list a logical offset of 0 is NOT the native origin:
+        // the native ScrollView rests at the opposite (max-offset) edge, so finishing
+        // "at origin" without scrolling leaves the list on the mirror end and the
+        // target index (e.g. initialScrollIndex 0) renders blank. Let the bootstrap
+        // dispatch run so the offset is converted to native RTL coordinates.
+        !isHorizontalRTL(state) &&
         (isOffsetInitialScrollSession(state)
             ? Math.abs(target.contentOffset ?? 0) <= 1
             : target.index === 0 && (target.viewPosition ?? 0) === 0 && Math.abs(target.viewOffset ?? 0) <= 1);
@@ -943,6 +950,12 @@ export function evaluateBootstrapInitialScroll(ctx: StateContext) {
     if (
         Platform.OS !== "web" &&
         Platform.OS !== "android" &&
+        // For a horizontal RTL list the mount seed and observed offset are logical 0,
+        // but the native origin is the opposite (max-offset) edge — so "already at the
+        // resolved offset" is a false positive and finishing without a scroll leaves
+        // index 0 blank. Always dispatch for horizontal RTL (which converts logical 0
+        // to the native RTL coordinate). Mirrors the shouldFinishAtOrigin guard above.
+        !isHorizontalRTL(state) &&
         Math.abs(bootstrapInitialScroll.seedContentOffset - resolvedOffset) <= 1 &&
         Math.abs(getObservedBootstrapInitialScrollOffset(state) - resolvedOffset) <= 1
     ) {

src/core/checkFinishedScroll.ts

@@ -6,6 +6,7 @@ import { initialScrollCompletion, initialScrollWatchdog } from "@/core/initialSc
 import { Platform } from "@/platform/Platform";
 import { getContentSize } from "@/state/getContentSize";
 import type { StateContext } from "@/state/state";
+import { toNativeHorizontalOffset } from "@/utils/rtl";
 
 type ActiveScrollTarget = NonNullable<StateContext["state"]["scrollingTo"]>;
 const INITIAL_SCROLL_MAX_FALLBACK_CHECKS = 20;
@@ -151,10 +152,16 @@ function checkFinishedScrollFrame(ctx: StateContext) {
 }
 
 function scrollToFallbackOffset(ctx: StateContext, offset: number) {
-    ctx.state.refScroller.current?.scrollTo({
+    const state = ctx.state;
+    const isHorizontal = !!state.props.horizontal;
+    // `offset` is a logical (LTR) offset. The normal dispatch path converts it to
+    // the native RTL coordinate; do the same here so the watchdog/retry doesn't
+    // dispatch an unconverted offset and land on the RTL mirror index.
+    const x = isHorizontal ? toNativeHorizontalOffset(state, offset, getContentSize(ctx)) : 0;
+    state.refScroller.current?.scrollTo({
         animated: false,
-        x: ctx.state.props.horizontal ? offset : 0,
-        y: ctx.state.props.horizontal ? 0 : offset,
+        x,
+        y: isHorizontal ? 0 : offset,
     });
 }