Deleting WebGL contexts

8
votes

I have a page that is using many many webgl contexts, one per canvas. canvases can be reloaded, resized, etc. each time creating new contexts. It works for several reloads, but eventually when I try to create a new context it returns a null value. I assume that I'm running out of memory.

I would like to be able to delete the contexts that I'm no longer using so I can recover the memory and use it for my new contexts. Is there any way to do this? Or is there a better way to handle many canvases?

Thanks.

2
memory-managementcanvaswebgl
The getContext() call is returning null, so the failure occurs when I try to set the viewport it errors because the object is null. - user2089247
Well you should be checking that your context is valid before doing anything else after your call to getContext() - Aesthete
It fails when the ~200th context is created. The first 199 are beautiful and wonderful. Code is pretty simple. - user2089247
try { gl = canvas.getContext("experimental-webgl"); gl.viewportWidth = 300; gl.viewportHeight = 150; } catch (e) { } if (!gl) { alert("Could not initialise WebGL, sorry :-("); } - user2089247
200 contexts? Simultaneously? - Aesthete

2 Answers

6
votes

This is a long standing bug in Chrome and WebKit

http://code.google.com/p/chromium/issues/detail?id=124238

There is no way to "delete" a context in WebGL. Contexts are deleted by garbage collection whenever the system gets around to it. All resources will be freed at that point but it's best if you delete your own resources rather than waiting for the browser to delete them.

As I said this is a bug. It will eventually be fixed but I have no ETA.

I would suggest not deleting canvases. Keep them around and re-use them.

Another suggestion would be tell us why you need 200 canvases. Maybe the problem you are trying to solve would be better solved a different way.

4
votes

I would assume, that until you release all the resources attached to your context, something will still hold references to it, and therefore it will still exist.

A few things to try:

  • Here is some debug gl code. There is a function there to reset a context to it's initial state. Try that before deleting the canvas it belongs to.

  • It's possible that some event system could hold reference to your contexts, keeping them in a zombie state.

  • Are you deleting your canvases from the DOM? I'm sure there is a limit on resources the page can maintain in one instance.

SO was complaining that our comment thread was getting a bit long. Try these things first and let me know if it help.