x11-wm/kwinft: support mac_priority(4) on Wayland

https://blog.martin-graesslin.com/blog/2017/09/kwinwayland-goes-real-time/

x11-wm/kwinft/Makefile

@@ -1,7 +1,7 @@
 PORTNAME=	kwinft
 DISTVERSIONPREFIX=	${PORTNAME}@
 DISTVERSION=	5.27.0
-PORTREVISION=	1
+PORTREVISION=	2
 CATEGORIES=	x11-wm wayland
 
 MAINTAINER=	jbeich@FreeBSD.org

x11-wm/kwinft/files/patch-main__wayland.cpp

@@ -0,0 +1,36 @@
+- Emulate SCHED_RESET_ON_FORK via pthread_atfork
+- Switch to pthread_setschedparam as Linux sched_setscheduler
+  operates on threads contrary to POSIX
+
+--- main_wayland.cpp.orig	2023-02-17 14:50:58 UTC
++++ main_wayland.cpp
+@@ -58,7 +58,7 @@ along with this program.  If not, see <http://www.gnu.
+ #include <QDebug>
+ #include <QWindow>
+ 
+-#include <sched.h>
++#include <pthread.h>
+ #include <sys/resource.h>
+ 
+ #include <iostream>
+@@ -122,12 +122,17 @@ void gainRealTime()
+ namespace {
+ void gainRealTime()
+ {
+-#if HAVE_SCHED_RESET_ON_FORK
+     const int minPriority = sched_get_priority_min(SCHED_RR);
+     sched_param sp;
+     sp.sched_priority = minPriority;
+-    sched_setscheduler(0, SCHED_RR | SCHED_RESET_ON_FORK, &sp);
+-#endif
++    if (pthread_setschedparam(pthread_self(), SCHED_RR, &sp))
++        return;
++
++    pthread_atfork(NULL, NULL, []() {
++        sched_param sp;
++        sp.sched_priority = 0;
++        pthread_setschedparam(pthread_self(), SCHED_OTHER, &sp);
++    });
+ }
+ }
+ 

x11-wm/kwinft/pkg-message

@@ -36,6 +36,13 @@ Replace KWin in Plasma Desktop:
   $ pkg set -o x11-wm/plasma5-kwin:x11-wm/kwinft
   $ pkg upgrade -f kwinft
   $ pkg lock kwinft
+
+Improve Wayland responsiveness under high load:
+
+  $ sysrc kld_list+=mac_priority
+  $ service kld restart
+  $ pw groupmod realtime -m <user>
+  $ exit # log out to refresh group permissions
 EOM
 }
 ]