From e712f4aa1f514d5875cb322a58f564362682612e Mon Sep 17 00:00:00 2001
From: Vasily <vautkin@teknik.io>
Date: Thu, 18 Jul 2019 18:48:03 +0200
Subject: [PATCH] Reduce update rate of chaperone velocity modifiers

Having the application call Sync() every frame led to slowdowns on some
4 core CPUs and instant crashes on some older CPUs.

This makes the chaperone velocity modifier only update on every 101st
frame. This might not be the ideal framerate, but having it update every
frame makes the app crash on start for some users.

On Manjaro with a i7-6700K (4 cores) this led to instant crashes of
SteamVR+Steam+OVRAS, with a SEGFAULT in SteamVR.
Issue here:
https://github.com/OpenVR-Advanced-Settings/OpenVR-AdvancedSettings/issues/252
---
 src/tabcontrollers/ChaperoneTabController.cpp | 43 ++++++++++---------
 1 file changed, 22 insertions(+), 21 deletions(-)

diff --git a/src/tabcontrollers/ChaperoneTabController.cpp b/src/tabcontrollers/ChaperoneTabController.cpp
index 4fcf8f2..e23e72e 100644
--- a/src/tabcontrollers/ChaperoneTabController.cpp
+++ b/src/tabcontrollers/ChaperoneTabController.cpp
@@ -574,27 +574,6 @@ void ChaperoneTabController::eventLoopTick(
     float rightSpeed,
     float hmdSpeed )
 {
-    m_chaperoneVelocityModifierCurrent = 1.0f;
-    if ( m_enableChaperoneVelocityModifier )
-    {
-        float mod = m_chaperoneVelocityModifier
-                    * std::max( { leftSpeed, rightSpeed, hmdSpeed } );
-        if ( mod > 0.02f )
-        {
-            m_chaperoneVelocityModifierCurrent += mod;
-        }
-    }
-    float newFadeDistance = m_fadeDistance * m_chaperoneVelocityModifierCurrent;
-    if ( m_fadeDistanceModified != newFadeDistance )
-    {
-        m_fadeDistanceModified = newFadeDistance;
-        vr::VRSettings()->SetFloat(
-            vr::k_pch_CollisionBounds_Section,
-            vr::k_pch_CollisionBounds_FadeDistance_Float,
-            m_fadeDistanceModified );
-        vr::VRSettings()->Sync();
-    }
-
     if ( devicePoses )
     {
         m_isHMDActive = false;
@@ -687,6 +666,28 @@ void ChaperoneTabController::eventLoopTick(
 
     if ( settingsUpdateCounter >= k_chaperoneSettingsUpdateCounter )
     {
+        m_chaperoneVelocityModifierCurrent = 1.0f;
+        if ( m_enableChaperoneVelocityModifier )
+        {
+            float mod = m_chaperoneVelocityModifier
+                        * std::max( { leftSpeed, rightSpeed, hmdSpeed } );
+            if ( mod > 0.02f )
+            {
+                m_chaperoneVelocityModifierCurrent += mod;
+            }
+        }
+        float newFadeDistance
+            = m_fadeDistance * m_chaperoneVelocityModifierCurrent;
+        if ( m_fadeDistanceModified != newFadeDistance )
+        {
+            m_fadeDistanceModified = newFadeDistance;
+            vr::VRSettings()->SetFloat(
+                vr::k_pch_CollisionBounds_Section,
+                vr::k_pch_CollisionBounds_FadeDistance_Float,
+                m_fadeDistanceModified );
+            vr::VRSettings()->Sync();
+        }
+
         if ( parent->isDashboardVisible() )
         {
             vr::EVRSettingsError vrSettingsError;