fix: use world matrices in getSpaceFromAncestors for XRLayer positioning

XRLayers were incorrectly positioned when inside components that override
updateWorldMatrix (e.g., UIKit's Content component which applies layout
transforms like globalMatrix and childrenMatrix).

The previous implementation accumulated local matrices via premultiply(),
which missed any custom transforms applied during updateWorldMatrix().

This change switches to using matrixWorld directly, ensuring that any
custom matrix computations are properly reflected in XRLayer positioning.

Author: myers

packages/xr/src/space.ts

@@ -48,19 +48,31 @@ export function getSpaceFromAncestors(
   originReferenceSpace?: XRReferenceSpace,
   targetOffsetMatrix?: Matrix4,
 ) {
-  targetOffsetMatrix?.copy(object.matrix)
-  const result = getXRSpaceFromAncestorsRec(object.parent, targetOffsetMatrix)
-  if (result != null) {
-    return result
+  // Update world matrices to ensure they're current.
+  // This is critical for components that override updateWorldMatrix to apply
+  // custom transforms (e.g., UIKit's Content component applies layout transforms).
+  // The old approach of accumulating local matrices missed these overrides.
+  object.updateWorldMatrix(true, false)
+
+  const xrSpaceAncestor = findXRSpaceAncestor(object.parent)
+
+  if (xrSpaceAncestor != null) {
+    if (targetOffsetMatrix != null) {
+      xrSpaceAncestor.updateWorldMatrix(true, false)
+      // Compute offset: ancestor.matrixWorld^-1 * object.matrixWorld
+      targetOffsetMatrix.copy(xrSpaceAncestor.matrixWorld).invert().multiply(object.matrixWorld)
+    }
+    return xrSpaceAncestor.xrSpace
   }
+
   if (targetOffsetMatrix != null) {
     computeOriginReferenceSpaceOffset(object, origin, targetOffsetMatrix)
   }
   return originReferenceSpace
 }
 
 function computeOriginReferenceSpaceOffset(object: Object3D, origin: Object3D | undefined, target: Matrix4): void {
-  object.updateWorldMatrix(true, false)
+  // object.updateWorldMatrix already called in getSpaceFromAncestors
   if (origin == null) {
     target.copy(object.matrixWorld)
     return
@@ -71,16 +83,12 @@ function computeOriginReferenceSpaceOffset(object: Object3D, origin: Object3D |
   target.copy(origin.matrixWorld).invert().multiply(object.matrixWorld)
 }
 
-function getXRSpaceFromAncestorsRec(
-  object: Object3D | null,
-  targetOffsetMatrix: Matrix4 | undefined,
-): XRSpace | undefined {
+function findXRSpaceAncestor(object: Object3D | null): (Object3D & { xrSpace: XRSpace }) | undefined {
   if (object == null) {
     return undefined
   }
   if (object.xrSpace != null) {
-    return object.xrSpace
+    return object as Object3D & { xrSpace: XRSpace }
   }
-  targetOffsetMatrix?.premultiply(object.matrix)
-  return getXRSpaceFromAncestorsRec(object.parent, targetOffsetMatrix)
+  return findXRSpaceAncestor(object.parent)
 }