File 0001-Revert-platforms-x11-Force-glXSwapBuffers-to-block-w.patch of Package kwin5

From 412016f1b3acc9e5acc994627f9177b1cf6b32ea Mon Sep 17 00:00:00 2001
From: Fabian Vogt <fabian@ritter-vogt.de>
Date: Mon, 15 Apr 2019 08:52:34 +0200
Subject: [PATCH] Revert "[platforms/x11] Force glXSwapBuffers to block with
 NVIDIA driver"

This reverts commit 3ce5af5c21fd80e3da231b50c39c3ae357e9f15c.
---
 .../platforms/x11/standalone/glxbackend.cpp   | 22 ++++++++++++++-----
 1 file changed, 17 insertions(+), 5 deletions(-)

diff --git a/plugins/platforms/x11/standalone/glxbackend.cpp b/plugins/platforms/x11/standalone/glxbackend.cpp
index 70dba6000..eb2d46414 100644
--- a/plugins/platforms/x11/standalone/glxbackend.cpp
+++ b/plugins/platforms/x11/standalone/glxbackend.cpp
@@ -115,11 +115,6 @@ GlxBackend::GlxBackend(Display *display)
     , haveSwapInterval(false)
     , m_x11Display(display)
 {
-     // Ensures calls to glXSwapBuffers will always block until the next
-     // retrace when using the proprietary NVIDIA driver. This must be
-     // set before libGL.so is loaded.
-     setenv("__GL_MaxFramesAllowed", "1", true);
-
      // Force initialization of GLX integration in the Qt's xcb backend
      // to make it call XESetWireToEvent callbacks, which is required
      // by Mesa when using DRI2.
@@ -701,8 +696,25 @@ void GlxBackend::present()
                 glXWaitGL();
                 if (char result = m_swapProfiler.end()) {
                     gs_tripleBufferUndetected = gs_tripleBufferNeedsDetection = false;
+                    if (result == 'd' && GLPlatform::instance()->driver() == Driver_NVidia) {
+                        // TODO this is a workaround, we should get __GL_YIELD set before libGL checks it
+                        if (qstrcmp(qgetenv("__GL_YIELD"), "USLEEP")) {
+                            options->setGlPreferBufferSwap(0);
+                            setSwapInterval(0);
+                            result = 0; // hint proper behavior
+                            qCWarning(KWIN_X11STANDALONE) << "\nIt seems you are using the nvidia driver without triple buffering\n"
+                                              "You must export __GL_YIELD=\"USLEEP\" to prevent large CPU overhead on synced swaps\n"
+                                              "Preferably, enable the TripleBuffer Option in the xorg.conf Device\n"
+                                              "For this reason, the tearing prevention has been disabled.\n"
+                                              "See https://bugs.kde.org/show_bug.cgi?id=322060\n";
+                        }
+                    }
                     setBlocksForRetrace(result == 'd');
                 }
+            } else if (blocksForRetrace()) {
+                // at least the nvidia blob manages to swap async, ie. return immediately on double
+                // buffering - what messes our timing calculation and leads to laggy behavior #346275
+                glXWaitGL();
             }
         } else {
             waitSync();
-- 
2.20.1