From 9f13e9b26035984906896a56d64e85e11522c581 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Thomas=20L=C3=BCbking?= <thomas.luebking@gmail.com>
Date: Tue, 26 May 2015 22:52:16 +0200
Subject: [PATCH] WORKAROUND for nvidia VBO failures

When switching virtual terminals,
suspending to ram and resizing the
screen (GL viewport) at least the
nvidia driver moves VBO data between
the video RAM and the system heap -
and something about this isn't reliable:

An often perceived resulted are scattered
windows but it may also be the cause for
entirely black screens reported for same
occasions.

As a workaround, we hook into the GL debug
messages and filter them for the suspicious
message, then re-init VBOs

TODO:
figure whether that's our fault or nvidias

REVIEW: 123936
CCBUG: 344326

Patch applies to KWin 5.4
---
 scene_opengl.cpp | 31 ++++++++++++++++++++++++++++++-
 1 file changed, 30 insertions(+), 1 deletion(-)

diff --git a/scene_opengl.cpp b/scene_opengl.cpp
index c33f5ccc09..9f7399ee79 100644
--- a/scene_opengl.cpp
+++ b/scene_opengl.cpp
@@ -436,9 +436,11 @@ SceneOpenGL::SceneOpenGL(OpenGLBackend *backend, QObject *parent)
     }
 }
 
+static SceneOpenGL *gs_debuggedScene = nullptr;
 SceneOpenGL::~SceneOpenGL()
 {
     // do cleanup after initBuffer()
+    gs_debuggedScene = nullptr;
     SceneOpenGL::EffectFrame::cleanup();
     if (init_ok) {
         delete m_syncManager;
@@ -448,12 +450,32 @@ SceneOpenGL::~SceneOpenGL()
     }
 }
 
+static void scheduleVboReInit()
+{
+    if (!gs_debuggedScene)
+        return;
+
+    static QPointer<QTimer> timer;
+    if (!timer) {
+        delete timer;
+        timer = new QTimer(gs_debuggedScene);
+        timer->setSingleShot(true);
+        QObject::connect(timer, &QTimer::timeout, gs_debuggedScene, []() {
+            GLVertexBuffer::cleanup();
+            GLVertexBuffer::initStatic();
+        });
+    }
+    timer->start(250);
+}
+
 void SceneOpenGL::initDebugOutput()
 {
     const bool have_KHR_debug = hasGLExtension(QByteArrayLiteral("GL_KHR_debug"));
     if (!have_KHR_debug && !hasGLExtension(QByteArrayLiteral("GL_ARB_debug_output")))
         return;
 
+    gs_debuggedScene = this;
+
     // Set the callback function
     auto callback = [](GLenum source, GLenum type, GLuint id,
                        GLenum severity, GLsizei length,
@@ -469,10 +491,17 @@ void SceneOpenGL::initDebugOutput()
             qCWarning(KWIN_CORE, "%#x: %.*s", id, length, message);
             break;
 
+        case GL_DEBUG_TYPE_OTHER:
+            // at least the nvidia driver seems prone to end up with invalid VBOs after
+            // transferring them between system heap and VRAM
+            // so we re-init them whenever this happens (typically when switching VT, resuming
+            // from STR and XRandR events - #344326
+            if (strstr(message, "Buffer detailed info:") && strstr(message, "has been updated"))
+                scheduleVboReInit();
+            // fall through! for general message printing
         case GL_DEBUG_TYPE_DEPRECATED_BEHAVIOR:
         case GL_DEBUG_TYPE_PORTABILITY:
         case GL_DEBUG_TYPE_PERFORMANCE:
-        case GL_DEBUG_TYPE_OTHER:
         default:
             qCDebug(KWIN_CORE, "%#x: %.*s", id, length, message);
             break;