Merge pull request #1395 from cabanier/pen-ray

clarify the target ray origin of pen-like devices

index.bs

@@ -1852,7 +1852,7 @@ The <dfn attribute for="XRInputSource">handedness</dfn> attribute describes whic
 The <dfn attribute for="XRInputSource">targetRayMode</dfn> attribute describes the method used to produce the target ray, and indicates how the application should present the target ray to the user if desired.
 
   - <dfn enum-value for="XRTargetRayMode">gaze</dfn> indicates the target ray will originate at the viewer and follow the direction it is facing. (This is commonly referred to as a "gaze input" device in the context of head-mounted displays.)
-  - <dfn enum-value for="XRTargetRayMode">tracked-pointer</dfn> indicates that the target ray originates from either a handheld device or other hand-tracking mechanism and represents that the user is using their hands or the held device for pointing. The orientation of the target ray relative to the tracked object MUST follow platform-specific ergonomics guidelines when available. In the absence of platform-specific guidance, the target ray SHOULD point in the same direction as the user's index finger if it was outstretched.
+  - <dfn enum-value for="XRTargetRayMode">tracked-pointer</dfn> indicates that the target ray originates from either a handheld device or other hand-tracking mechanism and represents that the user is using their hands or the held device for pointing. The orientation of the target ray relative to the tracked object MUST follow platform-specific ergonomics guidelines when available. In the absence of platform-specific guidance, the target ray SHOULD point in the same direction as the user's index finger if it was outstretched. If the {{XRSystem}} determines that part of the handheld device is or becomes intended to contact real-world surfaces (such as a pen tip), the target ray MUST originate at that point.
   - <dfn enum-value for="XRTargetRayMode">screen</dfn> indicates that the input source was an interaction with the canvas element associated with an inline session's output context, such as a mouse click or touch event.
   - <dfn enum-value for="XRTargetRayMode">transient-pointer</dfn> indicates that the input source was generated as part of an operating system interaction intent rather than a specific piece of hardware. Some examples are user intents based on information too sensitive to expose directly such as gaze, synthesised inputs from web driver or inputs generated by assistive technologies. This should only be used for assistive technologies if it is also used as a primary input so as to not inadvertently indicate that assistive technology is being used as per the W3C design principals.