From dc870c52a953a8778899a3f57c32f8c053c8049b Mon Sep 17 00:00:00 2001
From: Alexey Knyazev <3479527+lexaknyazev@users.noreply.github.com>
Date: Mon, 4 Mar 2024 00:00:00 +0000
Subject: [PATCH] Add flow/throttle

---
 .../KHR_interactivity/Specification.adoc      | 41 +++++++++++++++++++
 1 file changed, 41 insertions(+)

diff --git a/extensions/2.0/Khronos/KHR_interactivity/Specification.adoc b/extensions/2.0/Khronos/KHR_interactivity/Specification.adoc
index 081887776b..5071a5c875 100644
--- a/extensions/2.0/Khronos/KHR_interactivity/Specification.adoc
+++ b/extensions/2.0/Khronos/KHR_interactivity/Specification.adoc
@@ -1761,3 +1761,44 @@ When any of the `<i>` input flows is activated:
 .. activate the `completed` output flow.
 3. If the `remainingInputs` value is not zero:
 .. activate the `out` output flow.
+
+===== Throttle
+
+[cols="1h,1,2"]
+|===
+| Type | `flow/throttle` | Activate the output flow unless it has been activated less than a certain time ago
+.2+| Input flow sockets
+|   `in`  | The entry flow into this node
+| `reset` | When this flow is activated, the output flow throttling state is reset
+| Input value sockets
+| `float duration` | The time, in seconds, to wait after an output flow activation before allowing subsequent output flow activations
+.2+| Output flow sockets
+| `out` | The flow to be activated if the output flow is not currently throttled
+| `err` | The flow to be activated if the `duration` input value is negative, infinite, or NaN
+| Output value sockets
+| `float lastRemainingTime` | The remaining throttling time, in seconds, at the moment of the last valid activation of the input flow or NaN if the input flow has never been activated with a valid `duration` input value
+|===
+
+The internal state of this node consists of an uninitialized _timestamp_ value of an implementation-defined high-precision type and a floating-point `lastRemainingTime` value initialized to NaN.
+
+When the `reset` input flow is activated:
+
+1. Reset the `lastRemainingTime` value to NaN.
+
+When the `in` input flow is activated:
+
+1. Evaluate the `duration` input value.
+2. If the `duration` input value is NaN, infinite, or negative,
+.. activate the `err` output flow and skip the next steps.
+3. If the `lastRemainingTime` value is not NaN:
+.. Let `elapsed` be a non-negative difference, in seconds, between the _timestamp_ and the current time.
+.. If `duration` is less than or equal to `elapsed`,
+... set the _timestamp_ value to the current time;
+... set the `lastRemainingTime` value to zero;
+... activate the `out` output flow.
+.. If `duration` is greater than `elapsed`,
+... set the `lastRemainingTime` value to the positive difference, in seconds, between `duration` and `elapsed`.
+4. If the `lastRemainingTime` value is NaN,
+.. set the _timestamp_ value to the current time;
+.. set the `lastRemainingTime` value to zero;
+.. activate the `out` output flow.