RFR: 8282104: Node zoom/rotate flickers on Raspberry Pi with Touchscreen

[Alexander Scherbatiy]

On Mon, 16 May 2022 12:46:46 GMT, Alexander Scherbatiy <alexsch at openjdk.org> wrote:

>> Zoomed/Rotated with two fingers rectangle flickers (unexpectedly becomes pretty small or large and then returns back to previous size several times during zooming/rotating) on a Raspberry Pi with Touchscreen.
>> 
>> The log with traced events shows that it is possible that only one ABS_MT_POSITION_X or ABS_MT_POSITION_Y can be sent for a given slot. In this case the corresponding omitted Y/X value is undefined and is assigned from ABS_Y/X value. This produces incorrect result for slots different from 0.
>> 
>> Example of the trace events log, enabled by `-Dmonocle.input.traceEvents.verbose=true -Dmonocle.input.traceEvents=true` flags:
>> 
>> traceEvent: Processing EV_ABS ABS_MT_SLOT 1 [index=48]
>> traceEvent: Processing EV_ABS ABS_MT_TRACKING_ID 302 [index=64]
>> traceEvent: Processing EV_ABS ABS_MT_POSITION_X 399 [index=80]
>> traceEvent: Processing EV_ABS ABS_MT_POSITION_Y 272 [index=96]
>> traceEvent: Processing EV_KEY BTN_TOUCH 1 [index=112]
>> traceEvent: Read EV_ABS ABS_MT_SLOT 0 [index=176]
>> traceEvent: Read EV_ABS ABS_MT_POSITION_Y 315 [index=192]
>> traceEvent: Read EV_ABS ABS_Y 315 [index=208]
>> traceEvent: Read EV_SYN SYN_REPORT 0 [index=224]
>> 
>> ...
>> 
>> traceEvent: Read EV_ABS ABS_MT_SLOT 1 [index=320]
>> traceEvent: Read EV_ABS ABS_MT_POSITION_Y 271 [index=336]
>> traceEvent: Read EV_ABS ABS_X 552 [index=352]
>> traceEvent: Read EV_ABS ABS_Y 322 [index=368]
>> traceEvent: Read EV_SYN SYN_REPORT 0 [index=384]
>> 
>> First both ABS_MT_POSITION_X/Y events with values x: 399 and y: 272 are received for the slot 1.
>> Next only ABS_MT_POSITION_Y with y: 271 value is received (which implies that the x value has not been changed) for the slot 1.
>> The x value is undefined in the LinuxStatefulMultiTouchProcessor.processEvents() loop and is unexpectedly assigned to the ABS_X 552 value which belongs to the slot 0.
>> 
>> The fix skips setting ABS_X/Y values for slots different from 0.
>
> The fix also fixes the first use case described in the JDK-8087370
> 
> 1. Consider you're touching the screen with two fingers, for example
> coordinates of one point is ~100,100 and second point is ~200,200.
> While still touching around the same points some events are reported with
> one or another point to be either 100,200 or 200,100.

> @AlexanderScherbatiy This pull request has been inactive for more than 4 weeks and will be automatically closed if another 4 weeks passes without any activity. To avoid this, simply add a new comment to the pull request. Feel free to ask for assistance if you need help with progressing this pull request towards integration!

Could you review the simple fix?

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PR Comment: https://git.openjdk.org/jfx/pull/737#issuecomment-1519638945