Fail early when creating QOpenGLVertexArrayObject

There is a significant performance regression with using
QOpenGLVertexArrayObject::Binder on platforms not supporting VAOs. This
is because of the function resolving/initialization in create which is
called once pr bind if d->vao == 0.

Change-Id: I74e77f50921116c306247dc371c68b287a2e22d7
Reviewed-by: Sean Harmer <sean.harmer@kdab.com>
Reviewed-by: Giuseppe D'Angelo <giuseppe.dangelo@kdab.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/src/gui/opengl/qopenglvertexarrayobject.cpp b/src/gui/opengl/qopenglvertexarrayobject.cpp
index 3b106fecf5..f39b10dc60 100644
--- a/src/gui/opengl/qopenglvertexarrayobject.cpp
+++ b/src/gui/opengl/qopenglvertexarrayobject.cpp
@@ -150,6 +150,11 @@ bool QOpenGLVertexArrayObjectPrivate::create()
         qWarning("QOpenGLVertexArrayObject::create() requires a valid current OpenGL context");
         return false;
     }
+
+    //Fail early, if context is the same as ctx, it means we have tried to initialize for this context and failed
+    if (ctx == context)
+        return false;
+
     context = ctx;
     QObject::connect(context, SIGNAL(aboutToBeDestroyed()), q, SLOT(_q_contextAboutToBeDestroyed()));