Android: very rare: SDL_CreateWindow fails with "Could not fetch native window"

[bostick]

Very rarely, in the Android app that I'm developing, I see SDL_CreateWindow fail with "Could not fetch native window".

I can never reproduce the error, but I am interested in tracking it down and learning the root cause.

I wondered if there is race condition with threads, but I do not see how anything could cause the error.

Are there any ideas / suggestions for tracking this down?

[slouken]

@1bsyl, any ideas?

[1bsyl]

SDL_CreateWindow, and also SDL_CreateRenderer can only be called while the activity is i foreground.
it can be reproduced, if you start the app from command line with adb ( adb shell am start -n $PACKAGE_NAME/.MainActivity ) while the device is locked screen for instance.

(doesn't seem to be reproduced with testsprite .. (maybe render should be set to GLES2) ? but on my app this is 100% reproducible)

In SDL code, we use Android_WaitActiveAndLockActivity(). to wait for the activity to be in resume state.

Since the Main C Thread has started, onResume() has been called, so Android_Paused == false.

But the SDL window is not created and maybe don't have the events from the life cycle.
In the log cat, it appears there is an immediate onResume(), onPause().
We usually poll event after creating the SDL window, so we haven't handle the lifecycle event yet and the callback Android_OnPause() is not called, so Android_WaitActiveAndLockActivity() thinks it is still in Resume state.

[1bsyl]

@bostick and @slouken , ok this fixes the issue: we pump lifecycle events, to have an Android_Paused correct.
so that: it is in Paused, we can really wait normally.

[1bsyl]

@bostick please give a try. on my side, I've tested it and this works better with that.

[bostick]

@1bsyl Thank you for looking into this. I have trouble reproducing the error to begin with, so I am hesitant making any statements about resolution. I will spend more time trying to reproduce the problem.

[1bsyl]

This makes sense.

You can add a sdl_delay of 5 sec. Put your app manually in background. So that sdl_createwindow occurs in background.

[bostick]

I have had some luck with generating errors by using this procedure:

• start app

• quickly hit Home

• hit Recents

• hit app

• quickly hit Home

• hit Recents

• hit app

• etc.

My app has a 3 second splash screen that gives enough time to do several of these cycles and hit interesting errors.

I have encountered these errors while doing the above procedure:

• glClear giving GL_OUT_OF_MEMORY (my code calls glClear)

• SDL_GL_SwapWindow giving "unable to show color buffer in an OS-native window (call to eglSwapBuffers failed, reporting an error of EGL_BAD_SURFACE)"

• SDL_CreateWindow giving "Could not fetch native window"

The glClear and SDL_GL_SwapWindow errors seem more "low-level" than the SDL_CreateWindow error, but that is just a feeling.

We can open new issues to discuss them.

It is hard to generate any errors, but tentatively, there is good news:

Before your patch, "Could not fetch native window" was the most common error.

After your patch, I have not seen "Could not fetch native window" generated.

This is good evidence that the patch fixes the "Could not fetch native window" error!

I do not understand the responsible code, so I defer to others for resolving etc.

[slouken]

@1bsyl, thanks for the patch! This is merged and cherry-picked for the next SDL release.