OpenGLContext: Only create and use a VAO in contexts using the core profile

modules/juce_opengl/opengl/juce_OpenGLContext.cpp

@@ -409,7 +409,7 @@ public:
 
     void bindVertexArray() noexcept
     {
-        if (openGLVersion.major >= 3)
+        if (shouldUseCustomVAO())
             if (vertexArrayObject != 0)
                 context.extensions.glBindVertexArray (vertexArrayObject);
     }
@@ -616,9 +616,7 @@ public:
 
         gl::loadFunctions();
 
-        openGLVersion = getOpenGLVersion();
-
-        if (openGLVersion.major >= 3)
+        if (shouldUseCustomVAO())
         {
             context.extensions.glGenVertexArrays (1, &vertexArrayObject);
             bindVertexArray();
@@ -662,6 +660,31 @@ public:
         nativeContext->shutdownOnRenderThread();
     }
 
+    /*  Returns true if the context requires a non-zero vertex array object (VAO) to be bound.
+
+        If the context is a compatibility context, we can just pretend that VAOs don't exist,
+        and use the default VAO all the time instead. This provides a more consistent experience
+        in user code, which might make calls (like glVertexPointer()) that only work when VAO 0 is
+        bound in OpenGL 3.2+.
+    */
+    bool shouldUseCustomVAO() const
+    {
+       #if JUCE_OPENGL_ES
+        return false;
+       #else
+        clearGLError();
+        GLint mask = 0;
+        glGetIntegerv (GL_CONTEXT_PROFILE_MASK, &mask);
+
+        // The context isn't aware of the profile mask, so it pre-dates the core profile
+        if (glGetError() == GL_INVALID_ENUM)
+            return false;
+
+        // Also assumes a compatibility profile if the mask is completely empty for some reason
+        return (mask & (GLint) GL_CONTEXT_CORE_PROFILE_BIT) != 0;
+       #endif
+    }
+
     //==============================================================================
     struct BlockingWorker  : public OpenGLContext::AsyncWorker
     {
@@ -752,7 +775,6 @@ public:
     OpenGLContext& context;
     Component& component;
 
-    Version openGLVersion;
     OpenGLFrameBuffer cachedImageFrameBuffer;
     RectangleList<int> validArea;
     Rectangle<int> lastScreenBounds;