Touch events are fired twice when "Use mouse for touch" is on

Hi!
I’m making small demo-project for Windows 10 with multi-touch input support.
I handle generic touch input events such as TouchPressed, TouchMoved and TouchReleased in custom PlayerController blueprint. Then based on these events some maths is performed and my custom Tap or Zoom events are fired.

Before now I used mouse as touch input device by enabling “Use mouse for touch” checkbox in project settings. And everything worked fine. Only one “Touch pressed” event with finger index “Touch 1” was fired when I clicked the screen.

But now I’ve tested my project with “Use mouse for touch” enabled on 46’’ multi-touch monitor and have got strange results: there are two “Touch pressed” events are fired when I touch the screen and then two “Touch moved” events when I move my finger. First event has finger index “Touch 2” and second has “Touch 1” like the following:

Touch2 pressed at X=1133.200 Y=565.140
Touch2 moved to X=1125.700 Y=569.100
Touch1 pressed at X=1121.000 Y=569.000
Touch1 moved to X=1121.000 Y=569.000

Then I turned off “Use mouse for touch” setting and only one touch input is fired now. But it has “Touch 2” finger index. If I touch the screen with 2 or more fingers I get finger indices 2, 3, 4… not starting from 1.
I guess finger index 1 is “reserved” for mouse?

So, is it bug or feature?

Hello plastik21,

After doing some digging it appears that this is a known issue. I have provided a link to the public tracker. Please feel free to use the link provided for future updates.

Link: Unreal Engine Issues and Bug Tracker (UE-43213)

Make it a great day

Thank you for your additional information however, the issue above still appears to be the same issue (with the concerns mentioned above, this issue still fits).

Thanks for your answer. I saw this issue, and seems it’s related to UI system. In my case I don’t touch any UI elements, but static mesh object. However I use “Game And UI Input” mode (mb this can affect). And finally “double-touch” issue disappear when I turn off “Use mouse for touch” setting.