Why Instance Design

The scope of this wiki page is essentially to explain why JOGL uses a instance-design instead of a static one, used by other libraries (such as Lwjgl).

The content has been taken from this thread where Sven decided to elaborate and list the reasons behind that since many people wonder and ask why.

Then why does JOGL use Instances of GLContext / GL* instead of exposing a Static API?

Essentially because this is how it should be planned, doing differently is a wrong design. We are all about exposing a correct API, reflecting the real implementation model / design.

Answer: "Isn't static invocation faster?"

Question:

- OpenGL is a state machine. It associates locks and memory references and those OpenGL rendering states.

In JOGL, we do track certain states, required for a functional binding.

- [/deployment/jogamp-next/javadoc/jogl/javadoc/com/jogamp/opengl/GLBufferStorage.html GLBufferStorage] and its private tracker is used to manage memory mapped and use-create storage.

- Seamless FBO handling requires us to track currently used [[/deployment/jogamp-next/javadoc/jogl/javadoc/com/jogamp/opengl/GLBase.html#getDefaultDrawFramebuffer FBO buffer]

This allows us to pipe even onscreen rendering using FBO as required for certain machines (OSX/CALayer w/ AWT). However, this can be utilized by user applications, since tracking of the FBO is for free.

- [/deployment/jogamp-next/javadoc/jogl/javadoc/com/jogamp/opengl/GLSharedContextSetter.html Sharing GLContext, to allow seamless and stable context sharing, we are required to track its actual state to know when we are able to create the shared 'slave' context.

- Last but not least, GLContext performs proper locking. User can query states and try locking, as well as associate data to TLS.