From c08038e0a63f51202762fa72943d5cd3884a82f8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Thomas=20L=C3=BCbking?= <thomas.luebking@gmail.com>
Date: Sat, 9 May 2015 16:46:21 +0200
Subject: [PATCH] prefer query Screens::refreshRate()

ScreenInfo::rate is reporting 50Hz (on at least nvidia)
... AGAIN! * sigh*

In addition we check for __GL_SYNC_DISPLAY_DEVICE to pick
the rate of the screen that the driver will actually sync to
(hopefully...)

The patch is limited to nvidia systems for 5.3, applied everywhere
in master (ie. will be in 5.4 unless there's some problem)

BUG: 347360
REVIEW: 123693
---
 options.cpp | 32 ++++++++++++++++++++++++++++----
 1 file changed, 28 insertions(+), 4 deletions(-)

diff --git a/options.cpp b/options.cpp
index 7362c6b80a..804f05b7aa 100644
--- a/options.cpp
+++ b/options.cpp
@@ -29,6 +29,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #include <QProcess>
 
 #include "compositingprefs.h"
+#include "screens.h"
 #include "settings.h"
 #include "xcbutils.h"
 #include <kwinglplatform.h>
@@ -43,21 +44,44 @@ namespace KWin
 int currentRefreshRate()
 {
     int rate = -1;
-    if (options->refreshRate() > 0)   // use manually configured refresh rate
+    QString syncScreenName(QLatin1String("primary screen"));
+    if (options->refreshRate() > 0) {  // use manually configured refresh rate
         rate = options->refreshRate();
-    else if (Xcb::Extensions::self()->isRandrAvailable()) {
+    } else if (GLPlatform::instance()->driver() == Driver_NVidia &&
+               Screens::self()->count() > 0) {
+        // prefer the refreshrate calculated from the screens mode information
+        // at least the nvidia driver reports 50Hz BS ... *again*!
+        int syncScreen = 0;
+        if (Screens::self()->count() > 1) {
+            const QByteArray syncDisplayDevice(qgetenv("__GL_SYNC_DISPLAY_DEVICE"));
+            // if __GL_SYNC_DISPLAY_DEVICE is exported, the GPU shall sync to that device
+            // so we try to use its refresh rate
+            if (!syncDisplayDevice.isEmpty()) {
+                for (int i = 0; i < Screens::self()->count(); ++i) {
+                    if (Screens::self()->name(i) == syncDisplayDevice) {
+                        syncScreenName = Screens::self()->name(i);
+                        syncScreen = i;
+                        break;
+                    }
+                }
+            }
+        }
+        rate = qRound(Screens::self()->refreshRate(syncScreen)); // TODO forward float precision?
+    } else if (Xcb::Extensions::self()->isRandrAvailable()) {
+        // last restort - query XRandR screenInfo rate - probably wrong on nvidia systems
         Xcb::RandR::ScreenInfo screenInfo(rootWindow());
         rate = screenInfo->rate;
     }
 
     // 0Hz or less is invalid, so we fallback to a default rate
     if (rate <= 0)
-        rate = 60;
+        rate = 60; // and not shitty 50Hz for sure! *grrr*
+
     // QTimer gives us 1msec (1000Hz) at best, so we ignore anything higher;
     // however, additional throttling prevents very high rates from taking place anyway
     else if (rate > 1000)
         rate = 1000;
-    qCDebug(KWIN_CORE) << "Vertical Refresh rate " << rate << "Hz";
+    qCDebug(KWIN_CORE) << "Vertical Refresh rate " << rate << "Hz (" << syncScreenName << ")";
     return rate;
 }