Managing opengl contexts for more than one window

jbb · 2016-08-19T16:19:58

How do people manage multiple opengl contexts, if in fact they do? My code has a 'Window' class, so, in theory at least, you can create two or more windows. Each window can have it's own pixel format and opengl context due to the way it works. Now the problem is that before making *every* call to opengl I have to check that the current gl context is the correct one, and if not do wglMakeCurrent to switch to it. Or else I have to make a function on 'Window' called something like 'makeActive' before I do any opengl operations on it. And be sure to always remember to do this. My question is how do people cope with this? Is doing this very slow? Or do people generally not support more than one context in a program? Secondly, it seems that on windows at least, you have to call opengl functions via function pointers obtained from wglGetProcAddress and those pointers can be *different* for each context if they have different pixel formats. I am using multisampled output window in my main window and intend in a debug mode to have a separate window that doesn't need to have that so I *will* be having different pixel formats. So I can't just slap them into a lot of global variables. How do people cope with this? Or do people in general decide that supporting multiple windows is more effort than it's worth and find alternative solutions?

Graphics and GPU Programming Programming OpenGL

Started by jbb August 11, 2016 10:52 AM

10 comments, last by JohnnyCode 7 years, 8 months ago

jbb

471

Author

August 13, 2016 07:26 AM

Thanks again all.

?Based on the comments I'm not going to try to support multiple windows :) My project doesn't need them anyway.

My problem is that I identified 'Window' as being a good abstraction of something I'd need my application to have and a common one. And once I did that it because natural to ask does it make sense to have more than one window in an application.... Yes, it makes sense.
And then the issue of how to implement it nagged and nagged at me leading to complete coding paralysis!

I have decided that I have no need to implement multiple windows/contexts in my project so I will not do.
?Having decided that it seems natural to merge window and context management into my 'Game' class as they don't really need their own identity and it's natural to have a single "Game" object created in a program but not so much a 'Window'

JohnnyCode

1,084

August 19, 2016 04:19 PM

Thanks again all.

?Based on the comments I'm not going to try to support multiple windows :) My project doesn't need them anyway.

You can render to any amount of windows by their window handle being identified and provided to a context, as context can get succesfully updated to output onto a new window.

This window can be a background of a modal form etc (I once even hijacked IE browser window to output my Present(), this was in DX though)

Multiple separate contexts do not make much sense unless they make sense.

Managing opengl contexts for more than one window

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Managing opengl contexts for more than one window

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