Tix Frequently Asked Questions
    Legal Issues
  [L.1]  
    Is Tix free software?
 ANSWER:  
    Tix is distributed under the same license as Tcl/Tk (a.k.a. BSD
    style license).  Application developers can freely redistribute
    Tix along with their products. 
    General Questions About Using The Tix Library
  [G.1]  
    What does the "
-disablecallback"
    option do?
 ANSWER:  
    Many Tix widgets have both a 
-value option and a
    
-command option. Any modification of the
    
-value will cause the -command callback
    to be executed. Sometimes this is undesirable. For example,
    calling "
config -value" inside the callback procedure
    will cause the callback to be re-entered and thus an infinite
    recursion. 
    The 
-disablecallback can be used to advoid this
    problem. When this option is set, the 
-command    callback will not be executed even if the -value of a widget is
    changed. Therefore, if you need to modify the -value of a widget
    inside its callback, do this:
    
    proc my_callback {w} {
	$w config -disablecallback true
	$w config value blah
	$w config -disablecallback false
    }
    
    If you find this too troublesome, you can call the command tixSetSilent:
    
    proc my_callback {w} {
	tixSetSilent $w blah
    }
    
  [G.2]  
    How do I set the width of the entry subwidget inside the tixControl widget?
 ANSWER:  
    You can use the option database or the -options flag to set the
    configuration options of the subwidgets. E.g: 
option add *TixControl*entry.width 10
  OR
tixControl .c -options {
   entry.width  10
}
  [G.6]  
    I am not using the tixForm geometry manager, but it is giving me
errors about TixForm. What happened?
 ANSWER:  
    When you get error messages like this:
 (TixForm) Error:Trying to use more than one geometry
           manager for the same master window.
           Giving up after 50 iterations.
    Most likely, the problem is when using tixLabelFrame widgets, you
    packed to the wrong frame: 
    This is WRONG:
   tixLabelFrame .d
        button .d.b
        pack .d.b 
This is the correct way:
   tixLabelFrame .d
        set f [.d subwidget frame]
        button $f.b
        pack $f.b
        pack .d 
    Remember you don't pack directly into a TixLabelFrame
    widget. Instead, you should pack into its 
frame    subwidget.
  [G.7]  
    How do I generate the 
tclIndex file for Tix?
 ANSWER:  
    Tix 
tclIndex files cannot be generated using the
    standard auto_mkindex procedure. You must use the tixindex program
    in the 
tools/ subdirectory in the Tix
    distribution. The syntax is 
    
 tixindex *.tcl
    
  [G.8]  
    Can I ignore the default arguments passed by the various
    
-command and -browsecmd options?
 ANSWER:  
    You can use the 
tixBreak command. For example:
 tixFileSelectDialog .c -command "puts foo; tixBreak"   [G.9]  
    What does 
tixWidgetDoWhenIdle do?
 ANSWER:  
    It does the same thing as tixDoWhileIdle (and "after -idle"). The
    difference is it takes its second argument as the name of a widget
    and executes this command only if the widget exists: i.e.: 
  tixWidgetDoWhenIdle tixComboBox::Update $w blah blah ..    will execute tixComboBox::Update only if $w exists. $w may be
    destroyed after tixWidgetDoWhenIdle is called but before an idle
    event happens.
  [G.10]  
    Why isn't such a feature in Tix? Will it be implemented?
 ANSWER:  
    Generally requests for new features are welcomed. You can submit
    your requests to 
http://tix.sourceforge.net http://tix.sourceforge.net  and
    we'll be happy to hear from you. 
    We can't guarantee to implement the requested features
    immediately. Usually it depends on how important the features. If
    the feature is requested by more people, it will usually get done
    faster.
    However, some frequently requested features probably won't be
    imlemented. Usually these features are cosmetic changes and:
    
    
 they do not add new capability to the widgets
    
 they are not universally liked
    
 they confuse the user.
    
    
    Some examples are:
    
    
 Different foreground and background colors for the
    NoteBook tabs
: having a lot of colors may antagonize the users
    that are "color haters"; also, the different colors don't make it
    easier for the user to locate the desired tab.
    
 Ring-binder metaphore for the NoteBook widget: a waste
    of screen real estate.
    
 Rows of tabs for the NoteBook widget: the user may be
    confused when the rows of tabs are switched. If you need to have a
    lot of tabs for the notebook, use the ListNoteBook widget instead.
    
  [G.11]  
    Who are using Tix in their software?
 ANSWER:  
See 
http://tix.sourceforge.nethttp://tix.sourceforge.net   [G.12]  
    I am using a DirList widget. When the user clicks on an item, the
    procedure of my 
-browsecmd gets called
    twice. However, I just want it to be called once.
 ANSWER:  
    The 
-browsecmd procedure is triggered by three types
    of events: 
<1>,
    
<ButtonRelease-1>, and
    
<B1-Motion>. When the user clicks on an entry,
    a 
<1> and a
    
<ButtonRelease-1> event will happen in rapid
    session, which causes your 
-browsecmd procedure to be
    called twice. 
    A crude fix for this problem is to ignore all the
    
<ButtonRelease-1> events. You can find out the
    event that triggers the 
-browsecmd procedure by the
    
tixEvent command. Here is an example:
    
    tixDirList .c -browsecmd Browse
    proc Browse {args} {
	if {[tixEvent type] == "
<ButtonRelease-1>"} {
	    return
	}
	# ....
    }
    
    However, the above solution is not perfect. For example, if the
    user clicks down the button at entry one, drags it over entries
    two and three and release it on top of entry three, the following
    events may be caused: 
    
        
 <1> on entry one.
        
 <B1-Motion> on entry two.
        
 <ButtonRelease-1> on entry three.
    
     Therefore, if you use the above method, the browse event on entry
    three will be lost! 
    To devise a better solution, it's better to understand the basic
    design conventions of a Tix-based GUI. Suppose we have a list of
    entries displayed in a listbox (or DirList, or HList). When the
    user clicks on an entry, the GUI usually responds by displaying a
    "
detailed view" of the entry. For example, if we put a list
    of file names in a listbox, when the user clicks on a file name,
    we display the contents of the file in a text window. If the user
    then clicks on another file name, the text window will load in the
    contents of the new file. 
    Now what happens if the user clicks on the same entry twice? Do we
    reload the contents of the file into the text window? This is
    usually unnecessary, inefficient and probably not what the user
    wants to do. The Tix convention is, when the user clicks on the
    same entry again, the detail view is not updated. If the user
    wants to force an update (e.g, the user knows the file's contents
    has been changed and wants to see the new version), he or she can
    double-click on the entry and the application will respond by
    redisplaying the detail view (reloading the file). 
    To implement this policy, the Browse procedure should be modified
    as the following:
    
    proc Browse {args} {
	global currentView
	set ent [tixEvent value]
	if {$ent == $currentView} {
	    # We have already displayed the detailed view of $ent.
	    #
	    return
	} else {
	    set currentView $ent
	    DisplayDetail $ent
	}
    }
    
   [G.13]  
    I get an error 
"can't read data(-value): no such element in
    array
" when I use the tixExFileSelectDialog.
 ANSWER:  
    If you use tixExFileSelectDialog like this:
	tixExFileSelectDialog .f -command foo
	foo {filename} {
	    destroy .f
	    do some other stuff ...
	}
 it will cause a Tcl error because the dialog assumes that it still
 exists after calling your command. This usually result in errors like
 this:
	can't read "data(-value)": no such element in array
	    while executing
	"set data(-selection) $data(-value)..."
	    (procedure "tixComboBox::SetValue" line 30)
  This "feature" is built into many Tix widgets and can't be fixed
  easily. To work around the problem, never destroy widgets inside
  -command calls. Usually you should unmap toplevel windows
  instead. If you must destroy widgets, do it with an "after"
  command. For example, the foo procedure should be rewritten as:
	foo {filename} {
	    wm withdraw .f
	    do some other stuff ...
	    after idle {if [winfo exists .f] {destroy .f}}
	}
  Execute the "after" command at the very end of the
  -command. Otherwise the idle handler may be activated by some
  "update" calls.
    Question About Porting to Specific Platforms/Software
  [P.1]  
    The configure script gave me strange errors.
 ANSWER:  
    The problem may be you have several operating systems sharing the
    same file system. Some people encounter error messages like this:
# ./configure --prefix=/usr/vendor/tcl
loading cache ./config.cache
checking for a BSD compatible install... /usr/bin/installbsd -c
checking for ranlib... ranlib
checking how to run the C preprocessor... cc -E
checking for unistd.h... ./configure[603]: "${ac_cv_header_$ac_safe+set}": bad
substitution
    The problem is at line 2, configure loaded in ./config.cache,
    which may have been created by a different operating system, with
    settings only usuable for that operating system. To get around
    this, you should type
make distclean
./configure
make all
  [P.5]  
    
Solaris 2.4:    Filenames in FileSelectBox are chopped off.
 ANSWER:  
    
Problem:    
    With Tix4.0a7 (and also with Tix4.0a6) on Solaris 2.4, when
    running the widget demo, in tixFileSelectBox, in the two scolling
    lists (for Files an Directories), some of the file and directory
    names have their first 2 letters chopped off. And some files are
    repeated.
    
     
    
Solution: tixwish has some conflicts with /usr/ucblib/libucb.so.1
    and you should not link it tixwish (you don't need it). Here is
    a solution provided by Charles L Ditzel
    (
charles@hanami.cyberspace.com):
    
    To fix the problem I was having, all I did was:
    
   unsetenv LD_LIBRARY_PATH
   set my PATH to something basic like:
     /usr/bin:/usr/ccs/bin:/bin:/usr/openwin/bin:/opt/SUNWspro/bin
   removed config.cache
   ./configure
   make clean
   make
    
 
    and now it works!! Must have been something in my old
    
PATH or LD_LIBRARY_PATH that was
    causing it to pick up 
/usr/ucblib/libucb.so.
    
  [P.7]  
    
I get a coredump as soon as tixwish starts up.
 ANSWER:  
     Try to get a backtrace of the stack when the core dump happens
     (with a debugger, for example). If the core dump happens right
     inside the call to 
Tk_ConfigureWidget() inside the
     file 
tixInit.c, then the problem is because you
     compiled 
libtk.a and libtix.a with
     different versions of the Th header file
     
tk.h. Delete all the .o files from the
     src directory of Tix, fix the Makefile so that now you can
     compile 
libtix.a with the same tk.h that you used to
     compile 
libtk.a.
