handling BTN_TOUCH in evdev driver

Adam Jackson ajax at nwnk.net
Mon Sep 22 07:33:31 PDT 2008

On Mon, 2008-09-22 at 08:56 +0200, Søren Hauberg wrote:
> Hi,
>   I've making some changes tu the usbtouchscreen module to handle
> calibration stuff (see another thread on this list). This module
> currently emits BTN_TOUCH whenever the user touches the screen (I
> haven't changed this). When I'm using the evdev X driver to handle the
> touch screen I can move the cursor just fine, but I can't click any
> buttons in GUI's such as KDE or GNOME. If I instead use the evtouch
> X11 driver this works fine. So, it seems the evtouch and the evdev
> drivers handle BTN_TOUCH differently. Is there a reason why the evdev
> driver handles BTN_TOUCH as it does, or is it simply because nobody
> has tested it with a touchscreen? If the current behavior is on
> purpose, then I don't think my approach with changing the kernel
> driver and relying on evdev in X will work.

How does evtouch distinguish between "I want to move the cursor here"
and "I want to click here"?

Other than that, there's no particularly deep reason to not treat
BTN_TOUCH as a click in evdev.  I did test evdev with a touchscreen, but
apparently the one I had would give you distinct events for BTN_LEFT
versus BTN_TOUCH.

- ajax
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