From 0788890233850ca598af55abe52641d7b4254f14 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Thomas=20L=C3=BCbking?= <thomas.luebking@gmail.com>
Date: Fri, 9 Oct 2015 18:44:10 +0200
Subject: [PATCH] re-detect triple-buffering after compositor resume

and also hint the proper blocking condition (if turning
off swap control)

The detection vars are global, but the swap control requirement
is not preserved, so the detection must re-occur.

Alternatively (and better) the swap control should be saved
and re-applied, but there's trouble on initial detection

CCBUG: 343184
REVIEW: 125659
---
 eglonxbackend.cpp | 11 ++++++++---
 glxbackend.cpp    | 10 +++++++---
 2 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/eglonxbackend.cpp b/eglonxbackend.cpp
index 03cd5259cb..990be752c0 100644
--- a/eglonxbackend.cpp
+++ b/eglonxbackend.cpp
@@ -68,12 +68,19 @@ EglOnXBackend::EglOnXBackend(xcb_connection_t *connection, Display *display, xcb
     setIsDirectRendering(true);
 }
 
+static bool gs_tripleBufferUndetected = true;
+static bool gs_tripleBufferNeedsDetection = false;
+
 EglOnXBackend::~EglOnXBackend()
 {
     if (isFailed() && m_overlayWindow) {
         m_overlayWindow->destroy();
     }
     cleanup();
+
+    gs_tripleBufferUndetected = true;
+    gs_tripleBufferNeedsDetection = false;
+
     if (m_overlayWindow) {
         if (overlayWindow()->window()) {
             overlayWindow()->destroy();
@@ -82,9 +89,6 @@ EglOnXBackend::~EglOnXBackend()
     }
 }
 
-static bool gs_tripleBufferUndetected = true;
-static bool gs_tripleBufferNeedsDetection = false;
-
 void EglOnXBackend::init()
 {
     if (!initRenderingContext()) {
@@ -343,6 +347,7 @@ void EglOnXBackend::present()
                     if (qstrcmp(qgetenv("__GL_YIELD"), "USLEEP")) {
                         options->setGlPreferBufferSwap(0);
                         eglSwapInterval(eglDisplay(), 0);
+                        result = 0; // hint proper behavior
                         qCWarning(KWIN_CORE) << "\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"
diff --git a/glxbackend.cpp b/glxbackend.cpp
index 5447bfe09d..4c9e78c962 100644
--- a/glxbackend.cpp
+++ b/glxbackend.cpp
@@ -117,6 +117,9 @@ GlxBackend::GlxBackend()
     init();
 }
 
+static bool gs_tripleBufferUndetected = true;
+static bool gs_tripleBufferNeedsDetection = false;
+
 GlxBackend::~GlxBackend()
 {
     if (isFailed()) {
@@ -127,6 +130,9 @@ GlxBackend::~GlxBackend()
     cleanupGL();
     doneCurrent();
 
+    gs_tripleBufferUndetected = true;
+    gs_tripleBufferNeedsDetection = false;
+
     if (ctx)
         glXDestroyContext(display(), ctx);
 
@@ -140,9 +146,6 @@ GlxBackend::~GlxBackend()
     delete m_overlayWindow;
 }
 
-static bool gs_tripleBufferUndetected = true;
-static bool gs_tripleBufferNeedsDetection = false;
-
 void GlxBackend::init()
 {
     initGLX();
@@ -636,6 +639,7 @@ void GlxBackend::present()
                         if (qstrcmp(qgetenv("__GL_YIELD"), "USLEEP")) {
                             options->setGlPreferBufferSwap(0);
                             setSwapInterval(0);
+                            result = 0; // hint proper behavior
                             qCWarning(KWIN_CORE) << "\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"