fix: overscanning for bidirectional layouts

Author: nwidynski

packages/@react-stately/virtualizer/src/OverscanManager.ts

@@ -35,23 +35,19 @@ export class OverscanManager {
     this.visibleRect = rect;
   }
 
-  getOverscannedRect(orientation: Orientation): Rect {
+  getOverscannedRect(): Rect {
     let overscanned = this.visibleRect.copy();
 
-    if (orientation === 'vertical' || this.velocity.y !== 0) {
-      let overscanY = this.visibleRect.height / 3;
-      overscanned.height += overscanY;
-      if (this.velocity.y < 0) {
-        overscanned.y -= overscanY;
-      }
+    let overscanY = this.visibleRect.height / 3;
+    overscanned.height += overscanY;
+    if (this.velocity.y < 0) {
+      overscanned.y -= overscanY;
     }
 
-    if (orientation === 'horizontal' || this.velocity.x !== 0) {
-      let overscanX = this.visibleRect.width / 3;
-      overscanned.width += overscanX;
-      if (this.velocity.x < 0) {
-        overscanned.x -= overscanX;
-      }
+    let overscanX = this.visibleRect.width / 3;
+    overscanned.width += overscanX;
+    if (this.velocity.x < 0) {
+      overscanned.x -= overscanX;
     }
 
     return overscanned;

packages/@react-stately/virtualizer/src/Virtualizer.ts

@@ -191,7 +191,7 @@ export class Virtualizer<T extends object, V> {
     if (isTestEnv && !(isClientWidthMocked && isClientHeightMocked)) {
       rect = new Rect(0, 0, this.contentSize.width, this.contentSize.height);
     } else {
-      rect = this._overscanManager.getOverscannedRect(this.layout.getOrientation!()!);
+      rect = this._overscanManager.getOverscannedRect();
     }
     let layoutInfos = this.layout.getVisibleLayoutInfos(rect);
     let map = new Map;