Updates break if another view creates/uses an EAGLContext

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Updates break if another view creates/uses an EAGLContext - bug?

(9 posts) (5 voices)

Started 2 years ago by Turtle
Latest reply from crmagicxxx

Tags:

Turtle
Member
I've found what appears to be a bug. It causes cocos to break (stop updating) if any other view creates and uses an EAGLContext.

The problem seems to be that the EAGLView cocos uses includes code to save and restore the context in its swapBuffers method (presumably, to prevent it from interfering with other views that are drawing to different contexts) but, if another view has changed the current context without restoring it, all of OpenGL functions called by cocos are done prior to the context being set by EAGLView in the swapBuffers method.

Is there a good reason the correct context isn't set before doing drawing? Moving this code from EAGLView's swapBuffers method into the mainLoop fixed the problem in my application. Specifically, I added
```
 
	EAGLContext *oldContext = [EAGLContext currentContext];
	if(oldContext != openGLView_.context) 
		[EAGLContext setCurrentContext:openGLView_.context]; 
```
to the front of mainLoop and
```
 
	if(oldContext != openGLView_.context) 
		[EAGLContext setCurrentContext:oldContext]; 
```
at the end, and removed the similar code for setting and restoring the context from the swapBuffers method.

Edit:
It occurs to me that creating textures with the wrong context will cause problems too. So simply moving the code as above does not fix everything.
Posted 2 years ago #
yarri
Member

Hi, I found it better to use two EAGLview classes in my case. Although I'm currently using cocos2D for my HUD in the 3D engine SIO2 and found a way to get it to work by hacking Director.m. Are you trying to run two cocos2D views or something else?

--yarri

Posted 2 years ago #
riq
Key Master

@turtle: look at the TexutreMgr.m file. It creates a context to create textures in another thread.

Posted 2 years ago #
ripp
Member

@yarri, I'm trying to add an additional EAGLview to a coocos2d view but I can't quite get my head around it yet. Do you mind sharing your method or maybe just pointing me in the right direction?

Posted 2 years ago #
yarri
Member

@ripp Hi, it's not clear what you're trying to do... I've done both of these:
1) Add an EAGLview as a subview to the existing cocos2d openGLview (ie., [[[Director sharedDirector] openGLview] addsubview: newOpenGLView] ), or
2) Force cocos2d to run within a new EAGLview class (ie., not using the cocos2d EAGLview, but something else)

For the first, you just need to make sure you don't have a name space conflict (the v.0.9 CC* namespace should help). The only issue with this approach is you can't draw on top of this new EAGLview class but there's tricks to fake that.

For the second, you need to hack cocos2D director. Here are the steps I took:
a) In your new EAGLview class createFramebuffer() method, initialize cocos2d normally
b) Update Director class initOpenGLViewWithView: method so it *only* loads the FPSLabel and returns - you don't want to attach in the cocos2d opengl view
c) Update Director class convertCoordinate: and winSize methods per the patch I posted: (Issue 149)
d) Update Director class end method to remove the [self detach] method
e) Update Director class mainLoop method to remove any unnecessary openGL calls & remove the swap buffers call

Easy!

--yarri

PS I used the first technique to show a "picture in picture" of a 3D view within cocos2d, whereas with the second I'm using cocos2d as my HUD for SIO2.

Posted 2 years ago #
ripp
Member

@yarri, Thanks for outlining these steps. I'm trying to accomplish method 2 to run cocos2d on top of FlowCover. I'll try out the method and report back. Much obliged.

Posted 2 years ago #
yarri
Member

@ripp: this might be easier to use... it's a UIView
http://apparentlogic.com/openflow/

--yarri

Posted 2 years ago #
ripp
Member
@yarri, thanks for the link! I had seen that during my search of the interwebs and was gonna be my backup plan. Your method 1 above got me thinking, and after a night of reading up and a little trial and error, I was able to make it work. Here's the code if anyone is interested in integrating FlowCover to a cocos2d project (the source for FlowCover can be found here).
```
-(void) ShowCoverFlow: (id) sender
{
	flowCoverView = [[[UIView alloc] initWithFrame:[[UIScreen mainScreen] bounds]] autorelease];

        testViewController = [[UIViewController alloc] init];
	FlowCoverViewController *flowCover;

	[flowCoverWindow addSubview:flowCoverView];
	[testViewController setView:flowCoverView];

	NSArray *array = [[NSBundle mainBundle] loadNibNamed:@"TestFC" owner:self options:nil];

	flowCover = [array objectAtIndex:0];
	[testViewController presentModalViewController:flowCover animated:YES];

 }
```
and to dismiss the view
```
[[self parentViewController] dismissModalViewControllerAnimated:YES];
```
If anyone sees anything here that would create a black hole and swallow my iPod I'd appreciate the feedback, and if I can figure out how to embed a short video I'll put one up.
Posted 2 years ago #
crmagicxxx
Member

Hey Ripp

Can you please try to update your cover flow implementation to work with latest cocos 0.99.0? I converting your project http://ripprapp.com/blog/?p=50 to newest cocos, but failed. Suppose it has something to do with new opengl states, but I am lost trying to make it work...

Thanks

Posted 1 year ago #

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