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Allow cancelling rAF callbacks from within rAF #1005

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Merged
merged 2 commits into from
Apr 21, 2020
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Allow cancelling rAF callbacks from within rAF #1005

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Allow cancelling rAF callbacks from within rAF
Manishearth Apr 21, 2020
56e0c03
Address review comments
Manishearth Apr 21, 2020
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13 changes: 7 additions & 6 deletions index.bs
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Expand Up @@ -857,7 +857,7 @@ callback XRFrameRequestCallback = void (DOMHighResTimeStamp time, XRFrame frame)

Each {{XRFrameRequestCallback}} object has a <dfn for="XRFrameRequestCallback">cancelled</dfn> boolean initially set to <code>false</code>.

Each {{XRSession}} has a <dfn>list of animation frame callbacks</dfn>, which is initially empty, and an <dfn>animation frame callback identifier</dfn>, which is a number which is initially zero.
Each {{XRSession}} has a <dfn>list of animation frame callbacks</dfn>, which is initially empty, a <dfn>list of currently running animation frame callbacks</dfn>, which is also initially empty, and an <dfn>animation frame callback identifier</dfn>, which is a number which is initially zero.

<div class="algorithm" data-algorithm="request-animation-frame">

Expand All @@ -879,7 +879,7 @@ The <dfn method for="XRSession">cancelAnimationFrame(|handle|)</dfn> method canc
When this method is invoked, the user agent MUST run the following steps:

1. Let |session| be the target {{XRSession}} object.
1. Find the entry in |session|'s [=list of animation frame callbacks=] that is associated with the value |handle|.
1. Find the entry in |session|'s [=list of animation frame callbacks=] and |session|'s [=list of currently running animation frame callbacks=] that is associated with the value |handle|.
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Nit: This could be an "or", since the value should not exist in both at once.

1. If there is such an entry, set its [=cancelled=] boolean to <code>true</code> and remove it from |session|'s [=list of animation frame callbacks=].

</div>
Expand All @@ -892,15 +892,16 @@ When an {{XRSession}} |session| receives updated [=viewer=] state for timestamp
1. If |session|'s [=pending render state=] is not <code>null</code>, [=apply the pending render state=].
1. If |session|'s {{XRSession/renderState}}'s {{XRRenderState/baseLayer}} is <code>null</code>, abort these steps.
1. If |session|'s [=XRSession/mode=] is {{XRSessionMode/"inline"}} and |session|'s {{XRSession/renderState}}'s [=XRRenderState/output canvas=] is <code>null</code>, abort these steps.
1. Let |callbacks| be a list of the entries in |session|'s [=list of animation frame callback=], in the order in which they were added to the list.
1. Set |session|'s [=list of currently running animation frame callbacks=] to be a copy of the list of the entries in |session|'s [=list of animation frame callbacks=], in the order in which they were added to the list.
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What's the reasoning behind the new copy here? We should be able to just move the pointer around, so to speak, right?

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Trying to preserve the clause that that list is in order of append, but really that's how lists work anyway so i don't think this is necessary.

1. Set |session|'s [=list of animation frame callbacks=] to the empty list.
1. Set |frame|'s [=active=] boolean to <code>true</code>.
1. Set |frame|'s [=animationFrame=] boolean to <code>true</code>.
1. [=XRFrame/Apply frame updates=] for |frame|.
1. For each entry in |callbacks|, in order:
1. If the entry's [=cancelled=] boolean is <code>true</code>, continue to the next entry.
1. [=Invoke the Web IDL callback function=], passing |now| and |frame| as the arguments
1. For each |entry| in |session|'s [=list of currently running animation frame callbacks=], in order:
1. If the |entry|'s [=cancelled=] boolean is <code>true</code>, continue to the next entry.
1. [=Invoke the Web IDL callback function=] for |entry|, passing |now| and |frame| as the arguments
1. If an exception is thrown, [=report the exception=].
1. Set |session|'s [=list of currently running animation frame callbacks=] to the empty [=/list=].
1. Set |frame|'s [=active=] boolean to <code>false</code>.

</div>
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