[Tcl-bugs] [ tcl-Bugs-672526 ] X11 event lost with popen.

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Bugs item #672526, was opened at 2003-01-22 08:11
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Category: 02. Event Loops
Group: None
>Status: Pending
Resolution: Works For Me
Priority: 5
Submitted By: Gilles Noyer (gnoyer)
Assigned to: David Gravereaux (davygrvy)
Summary: X11 event lost with popen.

Initial Comment:
Hello 

  I have a problem on Windows XP and tcl 8.4.1
  The application is not refreshed after the end of an 
other application lauched with  the popen function.
  Moving the windows refresh the windows and permit to 
work again.
  The little sample show the problem.
  Click on the click button. This open notepad move the 
window notepad. Closing notepad not refresh the tcl 
windows and the application is not available.
  This problem is done on a lot of Windows XP stations.
  The problem is only in Windows XP and look like an 
X11 event problem.

  Thanks a lot.
Gilles Noyer



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>Comment By: David Gravereaux (davygrvy)
Date: 2003-01-28 01:27

Message:
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I can't reproduce it here, but I'll bet it's the call to [gets].  
notepad doesn't use pipes.  And not until that blocking gets 
call comes back does Tcl continue.  I'll bet money there is 
nothing wrong with Tcl_DoOneEvent or it's child 
Tcl_WaitForEvent.

I recommend not using pipes to an application that doesn't 
support pipes.

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Comment By: Gilles Noyer (gnoyer)
Date: 2003-01-28 01:22

Message:
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Sorry, I called "popen" the little code :
  set fid [open "| notepad" r ]
because in fact I want to open a GUI program having I/O to 
the standard chanel.

My application not use notepad but an other GUI program, 
and I want to have the result in the standart output when it 
finished.
In the program the "gets" is used to get the result of the GUI 
program. You are right in the sample it is not used.

My application work fine on Windows NT and 2000 but not in 
XP.


I know that Microsoft change some event strategy on XP.



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Comment By: Gilles Noyer (gnoyer)
Date: 2003-01-28 01:09

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more precisions :
This only a  XP problem.
To reproduce the problem the tcl windows need to be covered 
by the notepad window.
This problem is solved by setting "Windows NT compatibility" 
property flag to wish84.
The problem is random, try 3 times on a PC.
On some XP station I do not reproduce it.

This look like the X11 main loop event.

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Comment By: David Gravereaux (davygrvy)
Date: 2003-01-28 01:00

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in the test script is this line:
   set fid [open "| notepad" r ]

As notepad.exe does not write nor read anything to the 
standard channels that where provided to it by Tcl in 
notepad's STARTUPINFO when it was launched, I don't 
understand why pipes are being used for this.

Normally when a process is launched from wish, it is launch 
in a hidden and detached console (hides the new console 
window that would be blank anyway due to the redirection).  
But as notepad.exe is a GUI application, it comes to the 
foreground (not attached to the hidden console window) 
because it runs in the windows subsystem not the console 
subsystem.

Gilles, could you explain the problem a bit more?  Where is 
popen()?  In Tcl it is TclpCreateProcess(), but are you refering 
to something different?  Was notepad used just as a universal 
example, but the problem for you is with a different 
application?  Could a "launch" command that provides a 
different behavior without the pipe misunderstanding be more 
what you desire?  I'm actually surprised that [gets] is not 
blocking for you (or me).

IMHO, the fact that tcl can knowing launch a GUI application 
and has the nerve to set pipes to it, is a bad behavior.  Tcl 
read the PE header in ApplicationType(), so it could have 
grabbed the subsystem bit to see that it is GUI.  One day, I 
would to see this changed.

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Comment By: Jeffrey Hobbs (hobbs)
Date: 2003-01-27 17:33

Message:
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I tried this on Win2K and WinXP using the TDK2.5beta 
version of Tcl (8.4.1+) and don't have any problems.  Has 
anyone seem something similar?

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