Add support for querying "glxconfig" from native interface

This makes it possible to retrieve the GLXFBConfig used by Qt to
create the GLXContext. QtWebEngine on desktop needs this so that
Chromium can use the same config as Qt to eliminate BadMatch errors.

Change-Id: If18c0937b5af3e457ddbfda035e5d652230211c6
Reviewed-by: Laszlo Agocs <laszlo.agocs@digia.com>

src/plugins/platforms/xcb/qglxintegration.cpp

@@ -166,6 +166,7 @@ QGLXContext::QGLXContext(QXcbScreen *screen, const QSurfaceFormat &format, QPlat
                          const QVariant &nativeHandle)
     : QPlatformOpenGLContext()
     , m_screen(screen)
+    , m_config(0)
     , m_context(0)
     , m_shareContext(0)
     , m_format(format)
@@ -190,6 +191,7 @@ void QGLXContext::init(QXcbScreen *screen, QPlatformOpenGLContext *share)
         m_shareContext = static_cast<const QGLXContext*>(share)->glxContext();
 
     GLXFBConfig config = qglx_findConfig(DISPLAY_FROM_XCB(screen),screen->screenNumber(),m_format);
+    m_config = config;
     XVisualInfo *visualInfo = 0;
     Window window = 0; // Temporary window used to query OpenGL context
 
@@ -399,6 +401,8 @@ void QGLXContext::init(QXcbScreen *screen, QPlatformOpenGLContext *share, const
             qWarning("QGLXContext: Multiple configs for FBConfig ID %d", configId);
 
         config = configs[0];
+        // Store the config.
+        m_config = config;
     }
 
     Q_ASSERT(vinfo || config);

src/plugins/platforms/xcb/qglxintegration.h

@@ -72,6 +72,7 @@ public:
     bool isValid() const;
 
     GLXContext glxContext() const { return m_context; }
+    GLXFBConfig glxConfig() const { return m_config; }
 
     QVariant nativeHandle() const;
 
@@ -83,6 +84,7 @@ private:
     void init(QXcbScreen *screen, QPlatformOpenGLContext *share, const QVariant &nativeHandle);
 
     QXcbScreen *m_screen;
+    GLXFBConfig m_config;
     GLXContext m_context;
     GLXContext m_shareContext;
     QSurfaceFormat m_format;

src/plugins/platforms/xcb/qxcbnativeinterface.cpp

@@ -79,6 +79,7 @@ static int resourceType(const QByteArray &key)
         QByteArrayLiteral("display"),  QByteArrayLiteral("egldisplay"),
         QByteArrayLiteral("connection"), QByteArrayLiteral("screen"),
         QByteArrayLiteral("eglcontext"),
+        QByteArrayLiteral("glxconfig"),
         QByteArrayLiteral("glxcontext"), QByteArrayLiteral("apptime"),
         QByteArrayLiteral("appusertime"), QByteArrayLiteral("hintstyle"),
         QByteArrayLiteral("startupid"), QByteArrayLiteral("traywindow"),
@@ -240,6 +241,9 @@ void *QXcbNativeInterface::nativeResourceForContext(const QByteArray &resourceSt
     case EglContext:
         result = eglContextForContext(context);
         break;
+    case GLXConfig:
+        result = glxConfigForContext(context);
+        break;
     case GLXContext:
         result = glxContextForContext(context);
         break;
@@ -471,4 +475,17 @@ void *QXcbNativeInterface::glxContextForContext(QOpenGLContext *context)
 
 }
 
+void *QXcbNativeInterface::glxConfigForContext(QOpenGLContext *context)
+{
+    Q_ASSERT(context);
+#if defined(XCB_USE_GLX)
+    QGLXContext *glxPlatformContext = static_cast<QGLXContext *>(context->handle());
+    return glxPlatformContext->glxConfig();
+#else
+    Q_UNUSED(context);
+    return 0;
+#endif
+
+}
+
 QT_END_NAMESPACE

src/plugins/platforms/xcb/qxcbnativeinterface.h

@@ -63,6 +63,7 @@ public:
         Connection,
         Screen,
         EglContext,
+        GLXConfig,
         GLXContext,
         AppTime,
         AppUserTime,
@@ -104,6 +105,7 @@ public:
     static void setAppUserTime(QScreen *screen, xcb_timestamp_t time);
     static void *eglContextForContext(QOpenGLContext *context);
     static void *glxContextForContext(QOpenGLContext *context);
+    static void *glxConfigForContext(QOpenGLContext *context);
 
     Q_INVOKABLE void beep();
     Q_INVOKABLE bool systemTrayAvailable(const QScreen *screen) const;