CODEWITHSUNDEEP
opengljogl
Kan Li
Kan Li

Reputation: 8797

JOGL check extension availability before creating any GLCanvas

To check extension availability, I need to use GL.isExtensionAvailable. In order to get the GL object, I need to create some GLCanvas and get the GL instance in init() or display().

Is there a way to check the extension availability even before I create the window, at the beginning of main()?

Upvotes: 0

Views: 204

Answers (2)

gouessej
gouessej

Reputation: 4076

It's possible to call GLContext.getCurrent().getPlatformExtensionsString() very early but it will return a non null value only when the OpenGL context has been made current at least once and on the appropriate thread. Don't forget to call GLProfile.initSingleton() before calling GLContext.getCurrent().

However, pqnet's comment is correct. Numerous computers (especially modern laptops) have several graphics cards and mechanisms difficult to understand to switch to another one (for example Optimus) depending on the power consumption, the performance profile ("high performance" or not). Moreover, different drivers might be supported (the crappy GDI renderer and the true OpenGL driver under Windows), several profiles are often supported (forward compatible and backward compatible profiles, ES profiles even on desktop machines), ... JOGL will do its best to pick the most capable one but it can use different ones for offscreen and onscreen. The first OpenGL context used by GLProfile and the one used by the first created drawable can be very different.

This problem isn't only a problem with JOGL. My suggestion helps to know which extensions are available with the default device. You can use GLProfile.glAvailabilityToString() and GLProfile.getDefault() too.

N.B: I assume that you use at least JOGL 2.3.1. The maintenance of JOGL 1 was stopped about 5 years ago.

Upvotes: 0

pqnet
pqnet

Reputation: 6588

I guess you are out of luck. The availability of some extension may change according to which video card is connected to the screen you want to visualize your GL content, so you cannot get reliably that information before creating the GL context. You may be able to create an offscreen context only to get that information, however result may differ from a context bound to a window

Upvotes: 2

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