Output to text widget from C++ program 1

[edwong]

How do you output to to a text widget through a C++ program

Thanks

 

[Anto35]

Hi,
I redirect stdout to a file. Then I use Tcl events to know when the file is readable and when it changes. Finally you just have to write a callback which will fill the text widget with the content of the file.

I don't know if it's the best way to do that, but it works.
PS: Don't forget to unbuffer stdout (cf expect)

Example:
#######
# Set up to deliver file events on the pipe
fconfigure $fd -buffering line -blocking false -translation auto
fileevent $fd readable [list callback $fd $widg]
# Launch the event loop and wait for the file events to # finish
vwait :ONE

###
# And now the callback
####################
# fd is the file descriptor of the redirection of stdout
# Widg is the text widget
proc callback {fd widg} {
set status [catch {gets $fd line} result]
if { $status != 0 } {
# Error on the channel
$widg insert end "error reading $fd: $result"
set :ONE 2
} elseif { $result >= 0 } {
# Successfully read the channel
$widg insert end "$line\n"
$widg see end
} elseif { [eof $fd] } {
# End of file on the channel
close $fd
set :ONE 1
} elseif { [fblocked $fd] } {
# Read blocked. Just return
} else {
# Something else
tk_messageBox -title "Error" -message "can't happen!!!" -type "ok" -icon "error"
set :ONE 3
}
}

I hope this will help!

 

[Anto35]

Well, you can also use Tcl_Eval, if you want to modify your C code with Tcl C procedure.
Tcl_Eval(interp, "text_widget_name insert end {what you wanna see in your widget}&quot.

 

[AviaTraining]

Actuall, Anto35, while the first technique you described sounds like a perfectly reasonable application of the fileevent command, it isn't. Contrary to its name, fileevent works properly with every type of channel except a file. Check out the Tcl'ers Wiki (

http://wiki.tcl.tk),

at the bottom of the page "fileevent,"

http://mini.net/tcl/880,

for a discussion of this oddity.

Your second suggestion is actually the best way to handle inserting data from a C/C++ program into a text widget -- Tcl_Eval() or one of its relatives. - Ken Jones, President, ken@avia-training.com
Avia Training and Consulting,

http://www.avia-training.com

866-TCL-HELP (866-825-4357) US Toll free
415-643-8692 Voice
415-643-8697 Fax

 

[Anto35]

Thanx a lot Avia...
I improved the execution speed of my application with Tcl threads, but I understand that I lost my time because of the fileevent mechanism. Now I use 'after 100' to know when I've got to read stdout and I've got any speed problem no more!