Fix crashes and incorrect extension queries on GL3+

glGetString(GL_EXTENSIONS) is deprecated in OpenGL 3.0+.
This means that in core profiles on 3.2+ (or without the fwd
compatibility bit on 3.0/3.1), the call is not supported and may
return NULL. This causes a crash in at least one place where we
try to blindly strstr the result. The correct solution is to use
QOpenGLContext::extensions() and hasExtension() which is prepared
to handle GL3+.

Change-Id: I52fec7dcee001cdc0933af03f5eed4b7c822b2bb
Reviewed-by: Shawn Rutledge <shawn.rutledge@digia.com>
Reviewed-by: Gunnar Sletta <gunnar.sletta@jollamobile.com>
Reviewed-by: Sean Harmer <sean.harmer@kdab.com>

4 files changed, 10 insertions, 10 deletions

diff --git a/src/quick/items/context2d/qquickcontext2dtexture.cpp b/src/quick/items/context2d/qquickcontext2dtexture.cpp
index d3f2a956a3..ef1b65a04f 100644
--- a/src/quick/items/context2d/qquickcontext2dtexture.cpp
+++ b/src/quick/items/context2d/qquickcontext2dtexture.cpp
@@ -479,9 +479,9 @@ bool QQuickContext2DFBOTexture::doMultisampling() const
     static bool multisamplingSupported = false;
 
     if (!extensionsChecked) {
-        QList<QByteArray> extensions = QByteArray((const char *)glGetString(GL_EXTENSIONS)).split(' ');
-        multisamplingSupported = extensions.contains("GL_EXT_framebuffer_multisample")
-                && extensions.contains("GL_EXT_framebuffer_blit");
+        const QSet<QByteArray> extensions = m_context->glContext()->extensions();
+        multisamplingSupported = extensions.contains(QByteArrayLiteral("GL_EXT_framebuffer_multisample"))
+            && extensions.contains(QByteArrayLiteral("GL_EXT_framebuffer_blit"));
         extensionsChecked = true;
     }
 
diff --git a/src/quick/items/qquickshadereffectsource.cpp b/src/quick/items/qquickshadereffectsource.cpp
index 98203c51e5..f78a05ea9a 100644
--- a/src/quick/items/qquickshadereffectsource.cpp
+++ b/src/quick/items/qquickshadereffectsource.cpp
@@ -353,9 +353,9 @@ void QQuickShaderEffectTexture::grab()
             if (m_context->openglContext()->format().samples() <= 1) {
                 m_multisampling = false;
             } else {
-                QList<QByteArray> extensions = QByteArray((const char *)glGetString(GL_EXTENSIONS)).split(' ');
-                m_multisampling = extensions.contains("GL_EXT_framebuffer_multisample")
-                                && extensions.contains("GL_EXT_framebuffer_blit");
+                const QSet<QByteArray> extensions = m_context->openglContext()->extensions();
+                m_multisampling = extensions.contains(QByteArrayLiteral("GL_EXT_framebuffer_multisample"))
+                    && extensions.contains(QByteArrayLiteral("GL_EXT_framebuffer_blit"));
             }
             m_multisamplingChecked = true;
         }
diff --git a/src/quick/scenegraph/qsgdefaultglyphnode_p.cpp b/src/quick/scenegraph/qsgdefaultglyphnode_p.cpp
index ad0c9dad07..3267eeed83 100644
--- a/src/quick/scenegraph/qsgdefaultglyphnode_p.cpp
+++ b/src/quick/scenegraph/qsgdefaultglyphnode_p.cpp
@@ -206,7 +206,7 @@ void QSG24BitTextMaskShader::initialize()
     QSGTextMaskShader::initialize();
     // 0.25 was found to be acceptable error margin by experimentation. On Mac, the gamma is 2.0,
     // but using sRGB looks okay.
-    if (strstr((const char *) glGetString(GL_EXTENSIONS), "GL_ARB_framebuffer_sRGB")
+    if (QOpenGLContext::currentContext()->hasExtension(QByteArrayLiteral("GL_ARB_framebuffer_sRGB"))
             && m_glyphFormat == QFontEngine::Format_A32
             && qAbs(fontSmoothingGamma() - 2.2) < 0.25) {
         m_useSRGB = true;
diff --git a/src/quick/scenegraph/util/qsgpainternode.cpp b/src/quick/scenegraph/util/qsgpainternode.cpp
index ec44a994e0..b454f666ac 100644
--- a/src/quick/scenegraph/util/qsgpainternode.cpp
+++ b/src/quick/scenegraph/util/qsgpainternode.cpp
@@ -231,9 +231,9 @@ void QSGPainterNode::updateGeometry()
 void QSGPainterNode::updateRenderTarget()
 {
     if (!m_extensionsChecked) {
-        QList<QByteArray> extensions = QByteArray((const char *)glGetString(GL_EXTENSIONS)).split(' ');
-        m_multisamplingSupported = extensions.contains("GL_EXT_framebuffer_multisample")
-                && extensions.contains("GL_EXT_framebuffer_blit");
+        const QSet<QByteArray> extensions = m_context->openglContext()->extensions();
+        m_multisamplingSupported = extensions.contains(QByteArrayLiteral("GL_EXT_framebuffer_multisample"))
+            && extensions.contains(QByteArrayLiteral("GL_EXT_framebuffer_blit"));
         m_extensionsChecked = true;
     }