tracking cursor motion in a separate process

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2 total messages Started by david.a.copperman Wed, 06 Jan 1993 16:20

#1618

Author: david.a.copperman
Date: Wed, 06 Jan 1993 16:20

37 lines
2377 bytes

I posted this question to the net earlier.  I only got one response
(thanks, Dave S), and I think I phrased the question in a way that
made it appear rudimentary and therefore folks ignored it.  Please
try again - I need to know if I can do this before I commit to trying
to learn IV, which appears to be a major undertaking.

I have two processes, A and B.  A is written in X (no higher-level
packages).  It puts up a single window.  Process B forks and execs
A, and waits for it to come up.  Then it extracts the id (the X type
is Window) of A's window.  Process A (the graphics controller for
a geographical information system) operates under the control of B.
B needs to track cursor motion in A's window, so it (B) can do
real-time screen-to-world coordinate conversion and show the coordinates
in a window owned by B.

B is to be written in a higher-level package.  What I need to able to
do is assign the Window of A's window to some object/widget/etc. in B, 
then register for cursor motion events.  I understand that I can do
X-level programming in a program written in IV.  But it's very important
to me to not have to access the X event queue in code separate from
IV's code that does that - frankly, I'm not smart enough.  I want B's
code to be absolutely event driven, and simple enough that only one
entity (i.e., IV) need be involved in controlling the X event queue.
Is there some class in IV that I can use in this fashion?  More
specifically, can I create some object to which I can assign A's
Window, register for cursor motion in that window, and IV will call
the event handler for me?

A separate question:  B needs to be able to poll events going on in
other software having nothing to do with the screen.  I do that
in a prototype using Xt via Xt signal (alarm) handling, and it's fine.
Can I do some analog to this in IV?

Thanks very much.

Dave Copperman
dac@hoqaa.att.com

Re: tracking cursor motion in a separate process

#1622

Author: Mark Linton
Date: Wed, 06 Jan 1993 17:45

35 lines
2657 bytes

In article <1993Jan6.162051.471@cbfsb.cb.att.com>, dac@cbnewsf.cb.att.com (david.a.copperman) writes:
|> I have two processes, A and B.  A is written in X (no higher-level
|> packages).  It puts up a single window.  Process B forks and execs
|> A, and waits for it to come up.  Then it extracts the id (the X type
|> is Window) of A's window.  Process A (the graphics controller for
|> a geographical information system) operates under the control of B.
|> B needs to track cursor motion in A's window, so it (B) can do
|> real-time screen-to-world coordinate conversion and show the coordinates
|> in a window owned by B.
|> 
|> B is to be written in a higher-level package.  What I need to able to
|> do is assign the Window of A's window to some object/widget/etc. in B, 
|> then register for cursor motion events.  I understand that I can do
|> X-level programming in a program written in IV.  But it's very important
|> to me to not have to access the X event queue in code separate from
|> IV's code that does that - frankly, I'm not smart enough.  I want B's
|> code to be absolutely event driven, and simple enough that only one
|> entity (i.e., IV) need be involved in controlling the X event queue.
|> Is there some class in IV that I can use in this fashion?  More
|> specifically, can I create some object to which I can assign A's
|> Window, register for cursor motion in that window, and IV will call
|> the event handler for me?

It sounds like you would need to write a subclass of the InterViews Window
class that is given an initial X window id instead of getting one as
the result of creating a window.

|> A separate question:  B needs to be able to poll events going on in
|> other software having nothing to do with the screen.  I do that
|> in a prototype using Xt via Xt signal (alarm) handling, and it's fine.
|> Can I do some analog to this in IV?

Signals are a bit dangerous.  Seems like it would be safer to set a timeout
on the X input and then do your polling.  You can use the timer features
of Dispatcher to do this with InterViews.

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