From 19232dbe27521f60bdd265dbac0419d93c7ea5de Mon Sep 17 00:00:00 2001
From: VaL Doroshchuk <valentyn.doroshchuk@qt.io>
Date: Tue, 12 Mar 2019 10:28:46 +0100
Subject: Use QOpenGLContext::makeCurrent if QGLContext::makeCurrent failed
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If QPainterVideoSurface::setGLContext(QGLContext::currentContext()) is used
and no valid paint device has been provided to QGLContext, it fails to make the context current.
Thus there might be no available current context which might also produce crashes.

QGLContext::currentContext() creates QGLContext based on current QOpenGLContext instance,
and no paint device is available in QGLContext::device() in this case.

Currently QVideoWidget and QGraphicsVideoItem are effected.

It is relevant when a renderer calls currentContext->doneCurrent() before using the QPainterVideoSurface.
After this there is no any current context which could cause a crash, e.g. within compiling the shaders.

Task-number: QTBUG-74277
Change-Id: Ia28f4f6843a82a897399fd1ce2463e3b087b6437
Reviewed-by: Christian Strømme <christian.stromme@qt.io>
---
 src/multimediawidgets/qpaintervideosurface.cpp | 25 +++++++++++++++++--------
 1 file changed, 17 insertions(+), 8 deletions(-)

(limited to 'src/multimediawidgets')

diff --git a/src/multimediawidgets/qpaintervideosurface.cpp b/src/multimediawidgets/qpaintervideosurface.cpp
index e4762a7e1..440d5c858 100644
--- a/src/multimediawidgets/qpaintervideosurface.cpp
+++ b/src/multimediawidgets/qpaintervideosurface.cpp
@@ -62,6 +62,15 @@
 #include <QtDebug>
 QT_BEGIN_NAMESPACE
 
+static void makeCurrent(QGLContext *context)
+{
+    context->makeCurrent();
+
+    auto handle = context->contextHandle();
+    if (handle && QOpenGLContext::currentContext() != handle)
+        handle->makeCurrent(handle->surface());
+}
+
 QVideoSurfacePainter::~QVideoSurfacePainter()
 {
 }
@@ -395,7 +404,7 @@ QAbstractVideoSurface::Error QVideoSurfaceGLPainter::setCurrentFrame(const QVide
         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
     } else if (m_frame.map(QAbstractVideoBuffer::ReadOnly)) {
-        m_context->makeCurrent();
+        makeCurrent(m_context);
 
         for (int i = 0; i < m_textureCount; ++i) {
             glBindTexture(GL_TEXTURE_2D, m_textureIds[i]);
@@ -737,7 +746,7 @@ QAbstractVideoSurface::Error QVideoSurfaceArbFpPainter::start(const QVideoSurfac
 
     QAbstractVideoSurface::Error error = QAbstractVideoSurface::NoError;
 
-    m_context->makeCurrent();
+    makeCurrent(m_context);
 
     const char *program = 0;
 
@@ -862,7 +871,7 @@ QAbstractVideoSurface::Error QVideoSurfaceArbFpPainter::start(const QVideoSurfac
 void QVideoSurfaceArbFpPainter::stop()
 {
     if (m_context) {
-        m_context->makeCurrent();
+        makeCurrent(m_context);
 
         if (m_handleType != QAbstractVideoBuffer::GLTextureHandle)
             glDeleteTextures(m_textureCount, m_textureIds);
@@ -1115,7 +1124,7 @@ QAbstractVideoSurface::Error QVideoSurfaceGlslPainter::start(const QVideoSurface
 
     QAbstractVideoSurface::Error error = QAbstractVideoSurface::NoError;
 
-    m_context->makeCurrent();
+    makeCurrent(m_context);
 
     const char *fragmentProgram = 0;
 
@@ -1222,7 +1231,7 @@ QAbstractVideoSurface::Error QVideoSurfaceGlslPainter::start(const QVideoSurface
 void QVideoSurfaceGlslPainter::stop()
 {
     if (m_context) {
-        m_context->makeCurrent();
+        makeCurrent(m_context);
 
         if (m_handleType != QAbstractVideoBuffer::GLTextureHandle)
             glDeleteTextures(m_textureCount, m_textureIds);
@@ -1623,7 +1632,7 @@ void QPainterVideoSurface::setGLContext(QGLContext *context)
         //Set a dynamic property to access the OpenGL context
         this->setProperty("GLContext", QVariant::fromValue<QObject*>(m_glContext->contextHandle()));
 
-        m_glContext->makeCurrent();
+        makeCurrent(m_glContext);
 
         const QByteArray extensions(reinterpret_cast<const char *>(
                                         context->contextHandle()->functions()->glGetString(GL_EXTENSIONS)));
@@ -1734,13 +1743,13 @@ void QPainterVideoSurface::createPainter()
 #if !defined(QT_OPENGL_ES) && !defined(QT_OPENGL_DYNAMIC)
     case FragmentProgramShader:
         Q_ASSERT(m_glContext);
-        m_glContext->makeCurrent();
+        makeCurrent(m_glContext);
         m_painter = new QVideoSurfaceArbFpPainter(m_glContext);
         break;
 #endif // !QT_OPENGL_ES && !QT_OPENGL_DYNAMIC
     case GlslShader:
         Q_ASSERT(m_glContext);
-        m_glContext->makeCurrent();
+        makeCurrent(m_glContext);
         m_painter = new QVideoSurfaceGlslPainter(m_glContext);
         break;
     default:
-- 
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