[Gta04-owner] Using touchscreen as a touchpad?

Neil Jerram neil at ossau.homelinux.net
Thu Apr 21 15:28:59 CEST 2016

On 21/04/16 14:09, H. Nikolaus Schaller wrote:
> Hi Neil,
>> Am 21.04.2016 um 14:08 schrieb Neil Jerram <Neil.Jerram at metaswitch.com>:
>> Has anyone tried configuring the GTA04 touchscreen to behave as a
>> touchpad instead of a touchscreen?  Would the kernel code for the
>> touchscreen support that?
>> Subject to the latter, I think the former is possible in principle by
>> using libinput and configuring a udev rule like this:
>> ACTION=="add|change", KERNEL=="event[0-9]*", ENV{ID_VENDOR_ID}=="...",
>> (following
>> https://wayland.freedesktop.org/libinput/doc/latest/udev_config.html)
>> Also has anyone tried using an external input device instead of the
>> touchscreen?
> Not really, but using an OTG cable and an USB mouse should work out of
> the box. I think it does not even need special udev rules, although I have
> never tried.

Yes, agreed.  But a bit messy to have that cable hanging off the phone.  
Hence my interest either in bluetooth, or in a creative way of using the 
touchscreen that we already have.

> A bluetooth mouse should also work.

Yes, but in general I think the term 'mouse' implies needing a surface 
for the mouse to sit on - so not suitable for use when walking around.

> But: it might differ how user space software uses the touch. If it uses tslib
> the device name is usually hard-coded in some config.

But I believe tslib is obsolete now; I'm interested in a system using 
cutting edge Linux.

>   X11 will simply
> allow to move the cursor by any touch(screen/pad) device (but also depends
> on xorg.conf overrides).

Sure, yes.  But note the interesting difference between touchscreen and 
touchpads, which has prompted my question at the start of this thread.  
Touchscreen behaviour is that a touch on the screen generates a warp to 
that position followed by an immediate Button1 click.  Touchpad 
behaviour is that

- a drag on the screen will move the pointer by an amount proportional 
to the drag (but not _to_ the position where the finger ends)

- a hard enough 'tap' will generate a Button1 click.

So at the moment I'm wondering if touchpad behaviour might work more 
conveniently for me on the GTA04 than touchscreen.


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