Possible SDL2 issues introduced with P4A 2019.06.06

[jere-botes]

Kivy is an amazing framework and it is great that Kivy and P4A is moving forward and keeping up with the times. Unfortunately, I have been experiencing a few issues since moving from the “trusty and very stable P4A v0.6” to P4A 2019.06.06 and later.

My suspicion is that the issues might be related to SDL2 being upgraded from 2.0.4 to 2.0.9, as this seems to be the major variable that was changed from P4A 2019.06.06 onwards.

1. Severe drop in frame rate on android.

I have an app that requires moving around appx. 30-40 widgets at a fast pace. Previously (with P4A v0.6 & SDL2.0.4), I achieved 60fps without a hitch, but since the upgrade, building an apk using the exact same code the frame rate has dropped to less than 20fps.

Could this be SDL2 related, or something else?

2. App crashes on exit on android.

In the past I used one of two methods to gracefully exit an app:

Method 1

App.get_running_app().stop()
Window.close()

Method 2

import stopTouchApp kivy.base.stopTouchApp
stopTouchApp()

Since P4A 2019.06.06 and later releases, the app crashes on exit using these methods or causes and ANR on android (Tested on android 5.1 and android 9 – happens about 70% of the time.)

For the time being, I managed to circumvent the issue by running the exit code on UI thread eg: (It still crashes on exit sometimes, but much less frequently) Anyone with an idea why this happens?

3. Screen irregularities on android on_start and on_pause.

Using P4A 2019.06.06 or later, I have been noticing some issues with the Window / Screen on android device. The android status bar is shown on the splash screen while the app is loading – previously this was hidden. But, more importantly there intermittently appear a 'space' or 'black bar' at the top of the screen when on_resume is called causing the screen to ‘hop’ down and up, before being restored to normal. (Previously such screen transitions happened very smoothly, and was imperceptible.)

I created a minimal kivy app example to clearly demonstrate these issues on android. Please see built environment comparison below:

Test APK: KivyBench1 (No issues)
Build environment:

• VM: 0.4
• P4A: v0.6
• Kivy: 1.10.1
• Buildozer: 0.35
• API: 27
• NDK: Crystax 10.3.2
• Arch: armeabi-v7a

Test APK: KivyBench2 (Issues 1-3 as described previously)
Build environment:

• VM: 0.5
• P4A: v2019.07.08
• Kivy: 1.11
• Buildozer: 0.39
• API: 28
• NDK: r17c
• Arch: armeabi-v7a

Both apks are built with the exact same code, but if you run a performance test with KivyBench1 (built with P4A 0.6) with 100 widgets a frame rate of 60fps is achieved. Whereas, if you run KivyBench2 (built with P4A 2019.07.08) with 100 widgets, the frame rate is way down to 15 fps. (Tested with Android 9 device: Galaxy Note 9)

I also tried variations to build KivyBench2 for example changing Kivy version, NDK versions and all new P4A versions (2019.xx.xx), but the slow performance & other issues remain present. It looks like the issues is caused by the later versions of P4A, possibly SDL2 related… You will also notice the app crashes on exit with KivyBench2.

I’m attaching the app source code & sample apk packages etc, if anyone would like to build the apks to see if they get the same results.

LINK: https://github.com/jere-botes/KivyBench/

[inclement]

Thanks for the detailed report. I'll try to look into this.
@jtc0de have you seen anything like this during the SDL2 testing?

Hmmm I vaguely remember there being performance issues in between but I can't tell off the top of my head if that was ever in the specific version we use. (Since I'm usually ahead of p4a master anyway with the SDL2 version I use) The crash sounds like kivy maybe is accessing some UI things in a non main thread on shutdown?

As for the status bar, there definitely have been multiple issues with SDL2 with this I've witnessed on the SDL2 bugtracker, so if we simply bump up the SDL2 version this might easily go away. If not, then this and the perf issue most likely need to be addressed upstream. SDL2 has been quite responsive to android bugs recently, so it's all a matter of seeing if the latest version still has this and if it does, report it

[jere-botes]

Thanks for looking into this. I wish I could help, but unfortunately this is beyond my skill set…
The performance drop is quite severe in recent P4A versions. Even moving around as little as 15 widgets on screen, there is a perceptible drop in frame rate. This would badly affect any app that relies on minor animations etc.

Not sure if it will help, but here are some more info regarding my troubleshooting efforts:
I did tests building with arm64-v8a arch, hoping this might improve things, but has no effect.
The mentioned issues are all present in P4A 2019.06.06, 2019.07.08, 2019.08.06, but it seems there is a slight improvement in performance with P4A 2019.10.06 and the crashes / ANR's on exit are also less frequent.

[jere-botes]

I think I have made some progress in my pursuit to pinpoint where the performance issues come from...

I was able to build an apk version of ‘KivyBench’ using P4A_2019.08.09 but forced it to package with Kivy 1.10.1 instead of Kivy 1.11 as is the default with recent P4A releases.
I am happy to report that this gets rid of the very slow performance issue. Using 100 widgets again as an experiment appx 60 fps is achieved. (Using Kivy 1.11, achieves only +-15fps)

It seems however, that the recent P4A versions does not play nice with the older Kivy 1.10.1, as this brings about other issues, for example: screen orientation issues where even if you specify portrait, the app still opens in landscape. Anyone with an idea how this screen orientation can be fixed?

As for the performance issue, if looks like the issue lies with Kivy 1.11 and not P4A or SDL2 as I originally thought. Has anyone perhaps tried to test / recreate the performance issues mentioned in this thread?

[inclement]

Very interesting, thanks. If I have time I'll do some Kivy version comparisons. It ought to be possible to git bisect the slowdown, although it's inconvenient if it's necessary to build for android each time.

[inclement]

Anyone with an idea how this screen orientation can be fixed?

There were some specific commits, some by me, to make Kivy fully compatible with the newer SDL version. If you can find those commits, you can see what they changed.

[quitegreensky]

Yeah. The problem lies with current version of kivy. version 1.10.1 works fine! I'm facing with same issue

[jere-botes]

Just a quick update from my side…

Issue 1: Slow fps
Using the old Kivy 1.10.1 with P4A 2019.08.09 gets rid of the slow fps issues, but causes a problem with the screen orientation on android.
If it helps anyone, the screen orientation can be overridden in the SDLactivity.java file in the setOrientationBis() class – because the screen orientation setting in buildozer.spec file does not work anymore.

I don’t have any experience with java, but comparing the SDLacticity.java file from the stable P4A v0.6 with the SDLactivity.java file from the latest P4A 2019.08.09, I think this is also where the other two problems mentioned earlier in this thread is coming from…

Issue 2: Crashes on exit
The on_destroy method in SDLacticity.java has been rewritten in the latest P4A – Could there be an issue in the new java code that causes the crashes on exit?

Issue 3: Screen irregularities on android ‘sticky immersive’ mode
It also seems that there was a lot of changes made to SDLacticity.java with regard to the on_start, on_resume methods. Could it be that the rewritten methods are causing the screen issues on android immersive mode for example the status bar is shown intermittently on_start & on_resume causing the screen to ‘hop’ down & up and flash etc. Previously, the status bar was completely hidden and never ‘popped-up’ during screen transitions…

[jere-botes]

My 'issue 3', appears to be related to this thread:
#1117

The SYSTEM_UI_FLAG_FULLSCREEN flag in setSystemUiVisibility() is required to hide the status bar in android's 'sticky_immersive' mode. Although this is set in the onSystemUiVisibilityChange() class in SDLactivity.java, perhaps there is a problem with the implementation here that causes this issue...

[quitegreensky]

@inclement @jere-botes
Here is my update:
I did some version comparison and found that the fps regression issue comes from #4219. Every version before this commit works fine .

[inclement]

@quitegreensky Great work, thanks! I'll look at getting that revert in Kivy ASAP.

[yunus-ceyhan]

I emphasized this issue few monts ago on Kivy's discord channel but nobody beleved me even though i recorded a video to prove it. I knew soon or later every kivy developer would face that issue on android. I'm looking forward to a solution to be released regarding it which has made me stop developing apps with Kivy since then.

[quitegreensky]

@yunus-ceyhan Me too. I have opened a lot of issues in different places and it seemed no one is facing with this issue! But that was a BIG bug indeed so i tried to find the problem on my own and finaly i did . I solved this problem in my Kivy fork. You can use my fork for now.

[yunus-ceyhan]

@yunus-ceyhan Me too. I have opened a lot of issues in different places and it seemed no one is facing with this issue! But that was a BIG bug indeed so i tried to find the problem on my own and finaly i did . I solved this problem in my Kivy fork. You can use my fork for now.

thank you so much but i got that error.

https://paste.ubuntu.com/p/wjw2VjnwCB/