android: Assertion failure at SDL_AddTouch with Android API 28

[bostick]

Running the HelloWorld example on an Android API 28 device and getting this assertion failure:

Assertion failure at SDL_AddTouch (/Users/brenton/development/github/SDL/src/events/SDL_touch.c:170), triggered 1 time:
'touchID != 0'

the stack trace is:

SDL_AddTouch SDL_touch.c:172
Java_org_libsdl_app_SDLActivity_nativeAddTouch SDL_android.c:1083
Android_JNI_InitTouch SDL_android.c:2070
Android_InitTouch SDL_androidtouch.c:43
Android_VideoInit SDL_androidvideo.c:189
SDL_VideoInit SDL_video.c:705
SDL_InitSubSystem SDL.c:357
SDL_Init SDL.c:534
SDL_AppInit main.c:62
SDL_InitMainCallbacks SDL_main_callbacks.c:104
SDL_EnterAppMainCallbacks SDL_sysmain_callbacks.c:56
SDL_main SDL_main_impl.h:59
Java_org_libsdl_app_SDLActivity_nativeRunMain SDL_android.c:858

happens with API 28, but not API 29 or above

EDIT:
the original comment had this incorrect stack trace:

SDL_AddTouch SDL_touch.c:170
SDL_MouseTouchEventsChanged SDL_mouse.c:177
SDL_AddHintCallback SDL_hints.c:366
SDL_PreInitMouse SDL_mouse.c:288
SDL_VideoInit SDL_video.c:633
SDL_InitSubSystem SDL.c:357
SDL_Init SDL.c:534
SDL_main(int, char **) main.cpp:93
Java_org_libsdl_app_SDLActivity_nativeRunMain SDL_android.c:870

[1bsyl]

@bostick, are you sure of the stack trace, because:

In SDL_mouse.c, in SDL_MouseTouchEventsChanged(), the touch id is a constant:

SDL_AddTouch(SDL_MOUSE_TOUCHID, SDL_TOUCH_DEVICE_DIRECT, "mouse_input");

defined in SDL_touch.h:

typedef Uint64 SDL_TouchID;
#define SDL_MOUSE_TOUCHID ((SDL_TouchID)-1)

maybe your API 28 device, is an armv7a, 32bits.
and there is some cast underneath, 64 -> 32 bits.

what about testing to change in src/events/SDL_touch.c line ~172
SDL_assert(touchID != 0);
to
SDL_assert(touchID != 0L);

[bostick]

@1bsyl You are correct. SDL_AddTouch is called multiple times, and I originally included the first stack trace, not the asserting stack trace.

Comment is now updated with correct stack trace. Thank you.

I looked a little into this, and it is to do with output of InputDevice.getDeviceIds() (e.g. [-1, 0]) and deviceId of 0 slipping through and SDL_TouchID and SDL_FingerID treating 0 as invalid.

[1bsyl]

thanks !

https://developer.android.com/reference/android/view/InputDevice#getId()
doesn't say anything about id != 0 ..

So maybe we should +1 all positive ID.

BTW, I found this comment I wrote before, but removed, it could be still valid.

                int touchDevId = device.getId();
                /*
                 * Prevent id to be -1, since it's used in SDL internal for synthetic events
                 * Appears when using Android emulator, eg:
                 *  adb shell input mouse tap 100 100
                 *  adb shell input touchscreen tap 100 100
                 */
                if (touchDevId < 0) {
                    touchDevId -= 1;
                }
                nativeAddTouch(touchDevId, device.getName());
 

A patch would be something like:

               if (touchDevId < 0) {
                    touchDevId -= 1;
                } else {
                    touchDevId += 1;
               }

So it doesn't assert for 0 ...

[bostick]

I think 0 started being treated as an invalid value in this commit from Jan 2024:
a31dc6d

[slouken]

Yes, we do something similar for other platforms.

[1bsyl]

I ll make a patch and try again the "adb shell input touchscreen tap 100 100"

[1bsyl]

For the record, this is the list of device on emulator:

device.getId(): -1 device.getName(): Virtual
device.getId(): 0 device.getName(): qwerty2           (here, not added because not a SOURCE_TOUCHSCREEN)
device.getId(): 2 device.getName(): virtio_input_multi_touch_11
... many virtio_input_multi_touch_* ...
device.getId(): 12 device.getName(): virtio_input_multi_touch_1
device.getId(): 13 device.getName(): AT Translated Set 2 keyboard
device.getId(): 14 device.getName(): Power Button

with some command:

adb shell input mouse tap 100 100
-> not a touch
adb shell input touchscreen tap 100 100
-> device id=-1

@bostick
can you try the patch / PR ? #13716

also, wondering what is your device 0 ? in SDLActivity.java
Log.e("SDL", "device.getId(): " + device.getId() + " device.getName(): " + device.getName());

[bostick]

I printed this:

Log.e("SDL", "device.getId(): " + device.getId() +  " device.getName(): " + device.getName() + " touchscreen: " + ((device.getSources() & InputDevice.SOURCE_TOUCHSCREEN) == InputDevice.SOURCE_TOUCHSCREEN) + " device.isVirtual(): " + device.isVirtual());

My device 0:

device.getId(): 0 device.getName(): qwerty2 touchscreen: true device.isVirtual(): false

it IS a touchscreen source and slips through.

This is with an API 28 emulator, so it should be easy to reproduce.

[1bsyl]

there is the fact that device=0 triggers the assert so this should be fixed with the patch.

but maybe the qwerty shouldn't be added to SDL_TouchDevice. this sounds to be a keyboards and we dont want touch event for this I guess