From ac32664dc1356189d6a40923ecb2a6c392b0d9b9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Thomas=20L=C3=BCbking?= <thomas.luebking@gmail.com>
Date: Wed, 17 Jul 2013 15:44:42 +0200
Subject: [PATCH] keep buffer swap pref automatic until GPU detected

enforce to "e" (cheap) when driver is still unknown after
detection must be assumed to have run, so a sane value is available
when the context is up

BUG: 322355
FIXED-IN: 4.11
REVIEW: 111548
---
 eglonxbackend.cpp | 3 +++
 glxbackend.cpp    | 3 +++
 options.cpp       | 2 +-
 3 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/eglonxbackend.cpp b/eglonxbackend.cpp
index 86c763eb08..9af3c0d507 100644
--- a/eglonxbackend.cpp
+++ b/eglonxbackend.cpp
@@ -74,6 +74,9 @@ void EglOnXBackend::init()
     glPlatform->detect(EglPlatformInterface);
     if (GLPlatform::instance()->driver() == Driver_Intel)
         options->setUnredirectFullscreen(false); // bug #252817
+    options->setGlPreferBufferSwap(options->glPreferBufferSwap()); // resolve autosetting
+    if (options->glPreferBufferSwap() == Options::AutoSwapStrategy)
+        options->setGlPreferBufferSwap('e'); // for unknown drivers - should not happen
     glPlatform->printResults();
     initGL(EglPlatformInterface);
     if (!hasGLExtension("GL_OES_EGL_image")) {
diff --git a/glxbackend.cpp b/glxbackend.cpp
index 7f2449cfe4..11f7017bf5 100644
--- a/glxbackend.cpp
+++ b/glxbackend.cpp
@@ -97,6 +97,9 @@ void GlxBackend::init()
     glPlatform->detect(GlxPlatformInterface);
     if (GLPlatform::instance()->driver() == Driver_Intel)
         options->setUnredirectFullscreen(false); // bug #252817
+    options->setGlPreferBufferSwap(options->glPreferBufferSwap()); // resolve autosetting
+    if (options->glPreferBufferSwap() == Options::AutoSwapStrategy)
+        options->setGlPreferBufferSwap('e'); // for unknown drivers - should not happen
     glPlatform->printResults();
     initGL(GlxPlatformInterface);
     // Check whether certain features are supported
diff --git a/options.cpp b/options.cpp
index cd3931cd8d..8f6a21f474 100644
--- a/options.cpp
+++ b/options.cpp
@@ -767,7 +767,7 @@ void Options::setGlPreferBufferSwap(char glPreferBufferSwap)
         // see http://www.x.org/releases/X11R7.7/doc/dri2proto/dri2proto.txt, item 2.5
         if (GLPlatform::instance()->driver() == Driver_NVidia)
             glPreferBufferSwap = CopyFrontBuffer;
-        else
+        else if (GLPlatform::instance()->driver() != Driver_Unknown) // undetected, finally resolved when context is initialized
             glPreferBufferSwap = ExtendDamage;
     }
     if (m_glPreferBufferSwap == (GlSwapStrategy)glPreferBufferSwap) {