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Mouse events simulation doesn't work on Android 11 #3836

SDLBugzilla opened this issue Feb 11, 2021 · 0 comments

Mouse events simulation doesn't work on Android 11 #3836

SDLBugzilla opened this issue Feb 11, 2021 · 0 comments


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@SDLBugzilla SDLBugzilla commented Feb 11, 2021

This bug report was migrated from our old Bugzilla tracker.

These attachments are available in the static archive:

Reported in version: HG 2.1
Reported for operating system, platform: Android (All), All

Comments on the original bug report:

On 2020-10-02 20:47:18 +0000, Deve wrote:

I mean the events that are sent when SDL_HINT_TOUCH_MOUSE_EVENTS is enabled. On Android 11 it doesn't work anymore. It seems that Android doesn't report touch id, because the id is always -1, so that the


in SDL_SendTouch() SDL_touch.c:261 is never true and mouse event is never sent.

We have bug reports from some people that SuperTuxKart doesn't work on Android 11 (we use mouse events for GUI navigation).

I also reproduced it under emulator by using "input tap x y" command from adb shell (it was working on older versions, but didn't work on Android 11).

From what I understand the SDL_MOUSE_TOUCHID is just to avoid multiple events, that eg. mouse event simulates touch event, and then touch event shouldn't simulate mouse event again (true?).

As a quick fix we changed SDL_MOUSE_TOUCHID to different value, so that it doesn't conflict with the id=-1.

I can make a patch or make some tests, but do you have some particular fixes in mind? Add additional parameter to SDL_SendTouch() function for simulated events? Or just change SDL_MOUSE_TOUCHID value?

Btw. there are also some issues with gamepad support on Android 11, but I don't have real device to test... I will open separate bug report later.

On 2020-10-03 11:46:32 +0000, Sylvain wrote:

Just the context: SDL2 is creating Mouse (resp. Touch.) 'synthetic' events when the user move the real Touch (resp. Mouse) device. They appear with an id -1.
And only if the hints are enabled.
/* Used as the device ID for mouse events simulated with touch input /
#define SDL_TOUCH_MOUSEID ((Uint32)-1)
Used as the SDL_TouchID for touch events simulated with mouse input */
#define SDL_MOUSE_TOUCHID ((Sint64)-1)
See the hints:


you can add traces in public boolean onTouch(View v, MotionEvent event):
trace the value of "touchDevId", it should be a real value, not -1.

( )

But maybe the simulator reports a virtual device. And maybe you can dump the "event.getSource()" too.

(If needed, other places:
src/video/android/SDL_androidtouch.c: Android_OnTouchAndroid_OnTouch()
src/video/android/SDL_androidmouse.c: Android_OnMouse() )

Maybe there are stuff in the bug report:
"Android, some issue with InputDevice checks"
I saw various strange checks.

On 2020-10-04 09:23:15 +0000, Sylvain wrote:

If Android just send -1 as a valid id, the easiest patch for SDL2, would be to add:

"if (touchDevId < 0) touchDevId -= 1;"

So that -1 is restrict to the synthetic events.

Also, maybe please dump stuffs from "initTouch()"

On 2020-10-05 07:59:18 +0000, Sylvain wrote:

I tried with Android 11 emulator rev8, and I also got -1 id when using adb shell.
to send mouse and touch events.

When using the real mouse or real touch screen, it worked though.

Here's a fix, can you double check:

On 2020-10-05 08:32:42 +0000, Deve wrote:

I think just make sure that touchDevId is not equal to SDL_MOUSE_TOUCHID should be enough, so your fix should work. I will test today.

Though in theory it's possible on other platforms too, so maybe better use additional parameter, something like this?

int SDL_SendTouch(SDL_TouchID id, SDL_FingerID fingerid, SDL_Window * window, SDL_bool down, float x, float y, float pressure, bool simulated = false);

And are you able to test real gamepad device? It seems that it returns -1 too...

On 2020-10-05 17:32:23 +0000, Sylvain wrote:

  • We don't want to drop the -1 id coming from Android, it's valid even if it's a virtual device. we re-affect it to -2, and other n negative to n - 1. We keep -1 for internal sdl synthetic id.
    We could change the function, as well, not sure why we didn't do that.

I have no real android 11 so I used the emulator. Also I can't connect a gamepad and only use the shell commands.
id -1 seems to be the joystick named Virtual

This probably need to be changed to accept -1 :

I see the joystick appearing, but I could get it working neither with android 11 nor old android.

The check here might be wrong
could be:
int source = event.getSource();
if (source == InputDevice.SOURCE_JOYSTICK || source == InputDevice.SOURCE_GAMEPAD || source == InputDevice.SOURCE_DPAD) {

Just after, all MotionEvent.ACTION_* are not handle.
so, we might want to return "true" for ACTION_MOVE and false otherwise...
and/or move the code onNativePad{Up,Down} from SDLActivity.
Not really sure ...

On 2020-10-05 20:57:10 +0000, Deve wrote:

If you get Virtual -1, then it's the same what gets that guy on his Pixel 4 XL Phone with Android 11 and Logitech USB controller (see the screenshot).

And he already tested my quick fix with changing SDL_MOUSE_TOUCHID to different value and it fixed these mouse events for him. I can ask him to test your patch if you need to try it on real device.

I also tested your patch on android emulator and it works for me too.

On 2020-10-05 20:57:50 +0000, Deve wrote:

Created attachment 4474
screenshot gamepad

On 2020-10-06 06:17:54 +0000, Sylvain wrote:

Please don't use your patch (eg.
As a quick fix we changed SDL_MOUSE_TOUCHID to different value, so that it doesn't conflict with the id=-1. )

Ask the user to test:
with this first patch in

Also, in addition, with this second patch (to be made) to accept -1:

if ((device == null) || (deviceId < 0)) {
if (device == null) {

Please tell if all is ok with those two patches, thanks

On 2020-10-06 08:27:53 +0000, Sylvain wrote:

NB: by default, even on non Android 10, and without gamepad connected,
my phone report a device id with -1,

Virtual id=-1
device id == 769 (512 + 256 + 1)

which is CLASS={ BUTTON }
source(s): DPAD and KEYBOARD

So maybe your issue with gamepad, is totally different: HID not compiled ? gamecontrollerdb.h entry missing ?

On 2020-10-07 21:37:33 +0000, Deve wrote:

I asked that guy to test your patches, will tell you when I will get some information.

The "if (device == null)" will not work for multiple gamepads if all gamepads will have device id -1 (would be useful eg. on Android TV). But not sure how to solve it... if device id = -1 then generate id based on device name?

And I wonder if it's maybe a bug in android, because it's a bit strange behavior... I had a quick look and there is one related commit

But it's for injected events, so I'm not sure if/how it affects real touch/gamepad events.

@SDLBugzilla SDLBugzilla added the bug label Feb 11, 2021
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