Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!ispd-newsserver!ism.isc.com!ico!attc!marbru
From: marbru@attc.UUCP (Martin Brunecky)
Newsgroups: comp.windows.x
Subject: Re: Using tablets in X (Was: Re: Moving pointer in software ?)
Message-ID: <1295@attc.UUCP>
Date: 25 Mar 91 16:02:39 GMT
References: <9103131557.AA10051@devnull.Eng.Sun.COM> <1165@dandelion.CI.COM> <1991Mar18.170530.13580@dsd.es.com> <1276@attc.UUCP> <919@oliver.SUBLINK.ORG>
Reply-To: marbru@auto-trol.UUCP (Martin Brunecky)
Organization: Auto-trol Technology, Denver
Lines: 52

In article <919@oliver.SUBLINK.ORG> newsuser@oliver.SUBLINK.ORG (Ugo Cei) writes:
>You could also use a much more simple-minded approach: warp the
>pointer when the stylus or the mouse on the digitizer moves. You could
>create a program which reads the stylus position and outputs a couple
>of coordinates whenever the position changes. Your application has to
>open a connection to this program (e.g. using popen) and make the
>server listen to it (via XtAddInput).

   Using XtAddInput to "make server listen to it" ???
   I would more think of an independent program, communicating between
   the tablet and the server, running independently of the application.
   A simple tablet data collecting loop, generating XWarpPointer on
   a server connection.
   This would certainly do if the goal is only to move the pointer
   around, without any other application activity on the tablet (such
   as digitizing, menus, signature recognition ...).
>
>You also need to generate fake ButtonPress/Release events (via
>XSendEvent) when the user presses/releases the stylus or mouse
>button(s). If you send these events to the root window instead of your
>application's main window, you can control the entire X session using
>the digitizer, but beware that many applications require a three
>button mouse to work properly and even some key+button combinations.
>Also, when you stop moving the digitizer, you regain control of the
>pointer through the mouse.

   Mhmmm. I have some experience in this field ...
   First of all, sending events to the root window did not work for me.
   I had to find the topmost window above the pointer interested in the
   button event (even propagate was giving me a headache), to deliver
   my sent-event to the proper window and application. (Not many applications
   request button events on the root window of the screen).
   Next, the real problem are grabs. On the true button down event, the
   server grabs the pointer (and releases it on button up). So far, I haven't
   found a way to simulate this one - not even talking about the fact that
   while the simulated button down is "active", the user can press the 
   real button and confuse things even more.
   To summ it up, I have found that for many simple uses the "fake" button
   events do work. But not always. For example, window managers often do
   some magic on button downs  (such as grabbing the server) - so performing 
   (many of) WM functions through "fake" button events from the tablet simply 
   does not work.
   I suspect that the "real" solution here is to use something like XTest
   extension - but it again falls into the pitthole of which server supports
   which extension ....


-- 
=*= Opinions presented here are solely of my own and not those of Auto-trol =*=
Martin Brunecky                           {...}sunpeaks!auto-trol!marbru
(303) 252-2499                        (sometimes also:  marbru@auto-trol.COM )
Auto-trol Technology Corp. 12500 North Washington St., Denver, CO 80241-2404