Fix hand tracking visuals by deduplicating input sources across session arrays

Summary: Fixed an issue where hand tracking visuals were not displayed due to some WebXR runtimes including the same hands in both session.inputSources and session.trackedSources as different objects. Processing duplicates from trackedSources would overwrite the isPrimary flag, hiding hand visuals. The fix adds deduplication logic to skip reprocessing duplicates, preserving the correct isPrimary status.

Reviewed By: zjm-meta

Differential Revision:
D86931308

Privacy Context Container: L1334777

fbshipit-source-id: 5ebb295cd7fae786753d1c892c2e41330a25e201

Author: felixtrz

packages/xr-input/src/xr-input-manager.ts

@@ -100,6 +100,8 @@ export class XRInputManager {
   private scene: Scene;
   private hadSession = false;
 
+  private processedInputSourceKeys = new Set<string>();
+
   constructor(options: XRInputOptions) {
     const { scene, camera, assetLoader } = options;
     this.xrOrigin = new XROrigin();
@@ -227,13 +229,41 @@ export class XRInputManager {
     this.primaryInputSources.right = undefined;
   }
 
+  /**
+   * Updates the active input sources from the XR session.
+   *
+   * IMPORTANT: This method handles a platform quirk where some runtimes
+   * include the same hands in BOTH session.inputSources AND session.trackedSources.
+   * The duplicate entries represent the same physical hands but as different XRInputSource objects
+   * with different properties (e.g., different gamepad.buttons lengths).
+   *
+   * To prevent the trackedSources from overwriting the isPrimary status set by inputSources,
+   * we track which handedness+type combinations have already been processed and skip
+   * re-processing duplicates from trackedSources.
+   *
+   * Without this deduplication:
+   * - Hands from inputSources would be marked as isPrimary=true
+   * - Then the same hands from trackedSources would overwrite with isPrimary=false
+   * - This causes hand visuals to not be displayed (since visibility is tied to isPrimary)
+   */
   private updateActiveInputSources(session: XRSession): void {
+    this.processedInputSourceKeys.clear();
+
+    // Process inputSources (these are primary)
     for (const inputSource of session.inputSources) {
       this.assignInputSource(inputSource, true);
+      const key = `${inputSource.handedness}-${inputSource.hand ? 'hand' : 'controller'}`;
+      this.processedInputSourceKeys.add(key);
     }
+
+    // Process trackedSources (these are non-primary)
+    // Skip any that were already in inputSources to avoid overwriting isPrimary
     if (session.trackedSources) {
       for (const inputSource of session.trackedSources) {
-        this.assignInputSource(inputSource, false);
+        const key = `${inputSource.handedness}-${inputSource.hand ? 'hand' : 'controller'}`;
+        if (!this.processedInputSourceKeys.has(key)) {
+          this.assignInputSource(inputSource, false);
+        }
       }
     }
   }