Enable access to the VAO resolvers through QOpenGLContextPrivate

This is a commit in preparation for an upcoming change in QtQuick.
We want to store the resolved functions for managing VAOs somewhere;
the "least worst" choice is next to the all other function resolvers,
which are in QOpenGLContext(Private).

To avoid moving the VAO resolvers themselves, leave a hook in
QOGLCPrivate, similar to e.g. the texture function resolvers. The hook
gets populated when the VAO resolvers for a given context are
requested.

This removes memory management burden from the users of those functions
(again, just like other function resolvers), and makes the
initialization of the functions automatic.

Change-Id: I0eba30a85bf8ad82946a5d68e91009d8b4bd91cf
Reviewed-by: Laszlo Agocs <laszlo.agocs@qt.io>

2 files changed, 13 insertions, 0 deletions

diff --git a/src/gui/kernel/qopenglcontext.cpp b/src/gui/kernel/qopenglcontext.cpp
index d164f44e73..5c6d082f98 100644
--- a/src/gui/kernel/qopenglcontext.cpp
+++ b/src/gui/kernel/qopenglcontext.cpp
@@ -484,6 +484,13 @@ void QOpenGLContext::destroy()
     }
     d->textureFunctions = nullptr;
 
+    if (d->vaoHelperDestroyCallback) {
+        Q_ASSERT(d->vaoHelper);
+        d->vaoHelperDestroyCallback(d->vaoHelper);
+        d->vaoHelperDestroyCallback = nullptr;
+    }
+    d->vaoHelper = nullptr;
+
     d->nativeHandle = QVariant();
 }
 
diff --git a/src/gui/kernel/qopenglcontext_p.h b/src/gui/kernel/qopenglcontext_p.h
index ede41d5a93..c5f971fa4a 100644
--- a/src/gui/kernel/qopenglcontext_p.h
+++ b/src/gui/kernel/qopenglcontext_p.h
@@ -191,6 +191,7 @@ private:
 class QPaintEngineEx;
 class QOpenGLFunctions;
 class QOpenGLTextureHelper;
+class QOpenGLVertexArrayObjectHelper;
 
 class Q_GUI_EXPORT QOpenGLContextVersionFunctionHelper
 {
@@ -211,6 +212,8 @@ public:
         , functions(nullptr)
         , textureFunctions(nullptr)
         , versionFunctions(nullptr)
+        , vaoHelper(nullptr)
+        , vaoHelperDestroyCallback(nullptr)
         , max_texture_size(-1)
         , workaround_brokenFBOReadBack(false)
         , workaround_brokenTexSubImage(false)
@@ -242,6 +245,9 @@ public:
     QOpenGLTextureHelper* textureFunctions;
     std::function<void()> textureFunctionsDestroyCallback;
     QOpenGLContextVersionFunctionHelper *versionFunctions;
+    QOpenGLVertexArrayObjectHelper *vaoHelper;
+    using QOpenGLVertexArrayObjectHelperDestroyCallback_t = void (*)(QOpenGLVertexArrayObjectHelper *);
+    QOpenGLVertexArrayObjectHelperDestroyCallback_t vaoHelperDestroyCallback;
 
     GLint max_texture_size;