From ec56b2760a8754bdfded16e8979461506fcd0fab Mon Sep 17 00:00:00 2001
From: Geoffrey McRae <geoff@hostfission.com>
Date: Sat, 7 Aug 2021 03:39:11 +1000
Subject: [PATCH] [client] x11: don't allow window manager events to skew cal
 timing

---
 client/displayservers/X11/x11.c | 7 ++++++-
 client/displayservers/X11/x11.h | 2 ++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/client/displayservers/X11/x11.c b/client/displayservers/X11/x11.c
index 7c20bf5d..2c30e043 100644
--- a/client/displayservers/X11/x11.c
+++ b/client/displayservers/X11/x11.c
@@ -674,6 +674,8 @@ static int x11EventThread(void * unused)
 
       case ConfigureNotify:
       {
+        atomic_store(&x11.lastWMEvent, microtime());
+
         int x, y;
 
         /* the window may have been re-parented so we need to translate to
@@ -707,6 +709,7 @@ static int x11EventThread(void * unused)
 
       case Expose:
       {
+        atomic_store(&x11.lastWMEvent, microtime());
         app_invalidateWindow(false);
         break;
       }
@@ -1227,7 +1230,9 @@ static bool x11WaitFrame(void)
   lastmsc = msc;
 
   /* adjustments if we are still seeing odd skips */
-  if (delay > 0 && deltamsc > 1)
+  const uint64_t lastWMEvent = atomic_load(&x11.lastWMEvent);
+  const uint64_t eventDelta = ust > lastWMEvent ? ust - lastWMEvent : 0;
+  if (delay > 0 && deltamsc > 1 && eventDelta > 1000000UL)
   {
     /* only adjust if the last skip was less then 1s ago */
     static uint64_t lastSkip = 0;
diff --git a/client/displayservers/X11/x11.h b/client/displayservers/X11/x11.h
index 0fd6322f..820259c6 100644
--- a/client/displayservers/X11/x11.h
+++ b/client/displayservers/X11/x11.h
@@ -40,6 +40,8 @@ struct X11DSState
   Window        window;
   XVisualInfo * visual;
 
+  _Atomic(uint64_t) lastWMEvent;
+
   int               xpresentOp;
   bool              jitRender;
   _Atomic(uint64_t) presentMsc, presentUst;