Visual Tcl

Feb 26, 2016
Visual Tcl
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Frequently Asked Questions

General Tcl/Tk resources Tcl/Tk extensions with vtcl Vtcl questions Tcl/Tk questions

What is Vtcl?

Visual Tcl is a freely-available, high-quality application development environment for UNIX, Windows, Macintosh and AS400 platforms, says Stewart Allen, its developer.
With vTcl you can design not only the graphical view of your application, using visual tools and "What You See Is What You Get", but also write and test the Tcl procedures and TK events bindings that drive it.
You even have a "Test" button hat runs your application from within vTcl. When you are satisfied, you just save your work and it is ready to run.
The saved work contains no vTcl specific code, and if you find the need to edit it outside vTcl, you can do it and yet read it gain in vTcl.
If you have already a running application using pure Tcl/Tk code you can read it from within vTcl and continue developing it.

What do I need to run vTcl? What OS are supported?

You need Tcl/Tk installed. Tcl/Tk is available for most UNI*X, and for Windows and Mac also.

How can I reorganize the order of appearance of already created  widgets, or specify the place where a new widget  s to be inserted? I am using the packer.

Say that you have a frame with four buttons, A, B, C, D, packed in that order, and want to change the packing order to A,D,B,C.

  • You should have the "widget tree" window opened. Press the reload button before start.
  • Press the right mouse button on widget B, and choose "Hide". The button should disappear.
  • Repeat the procedure for button C
  • On the "widget tree" window, click on the button corresponding to widget B. It should appear now after widget D.
  • Repeat for widget D.
  • You should now have the widgets in the order A,D,B,C
The new order will be the order of the reappearance, so if you exchange points 2 and 3 above, you will end up with the buttons in the order A,D,C,B

This also applies to the insertion place order of new widgets. Hide all widgets after the one where you want to insert the new one, create it, and then click on the "widget tree" to unhide the previously hidden ones.
A much simpler approach, contributed by Grzegorz Popiela <> is as follow:

  • Select widget D
  • Press the Up arrow twice
  • You should now have the widgets in the order A,D,B,C

The Down arrow of course moves the widget down, and the Left and Right arrows sideways, if they are packed side by side.
This above applies also to menu entries.

How can I rapidly assign a scrollable widget with a scrollbar?

Right click on the scrollbar. From the menu select "Widget". Next select "Attach to Widget". Then select the widget you wish to attach the scrollbar to.

Can I use vtcl with tix or blt or itcl?

Yes. Support for them is already built-in in vtcl. At startup, vtcl tries to identify the tk interpreter that is driving it. If it is tix, vtcl will add some tix specific widgets to the widget window; the same for blt and itcl. The only think that you need to do is setting the PATH_TO_WISH variable in vtcl main script, usually found at /usr/local/bin/vtcl, e.g.,

----------------- vtcl -----------------------

#PATH_TO_WISH=/usr/local/bin/tixwish or whatever name
#PATH_TO_WISH=/usr/local/bin/bltwish or whatever name

-------------------- end of vtcl --------------

Grzegorz Popiela is working on a patch to vtcl to enable it working with iwidgets 3.0.

I have the tixwish interpreter and have tried setting the PATH_TO_WISH  variable in the vtcl script (as above), but I've run into problems. Vtcl seems to find the megawidgets well enough and adds them to
the widget toolbar .  Unfortunately, although the environment inserts a notebook widget (for example), I can't resize it graphically or delete it.

I think you will find that the notebook has already been placed in a frame of some sort. To move/resize the notebook, first select the notebook by clicking on it's icon in the widget tree window.  This will put the 8 move/resize blocks on the enclosing frame.  Then use the middle mouse button to move the whole note book and the left button to resize by click/drag on the 8 blocks, Peter Onion <> says.

OK, but then I only can use one of them. And what if I want to use widgets from two of them?

You have to build (dream) your own wish. For an example, search for the file tkAppInit.c in the source distribution of tix, blt or itcl and create your own wish. That's very simple if they are compatible...

[Please confirm this one, I have not tried it]

FAQ co-maintainer by appointment, Grzegorz Popiela :-), says:

You can use another script file instead of vtcl, lets call it `dream'. Create it according to the following recipe and make it executable:

---------------- start of dream ------------------------
# the next line restarts using wish \
exec wish "$0" "$@"

package require Iwidgets
package require Tix
package require BLT
# etc...

source ${VTCL_HOME}/vt.tcl
# where VTCL_HOME should be defined as in the standard `vtcl' file

----------------- end of dream -----------------------

Of course these extensions have to be compiled as loadable libraries (they usually are).

No, no, I want support for xxx.

Write it and submit your changes. Start by looking in the vtcl source distribution for lib_blt.tcl lib_core.tcl lib_itcl.tcl and lib_tix.tcl.

OK, you convinced me, how can I add support for new widgets?

Start looking in lib_blt.tcl lib_core.tcl lib_itcl.tcl and lib_tix.tcl.

What is the purpose of the menu entry "Set Insert"?

If you choose "Set Insert" from the menu, next widget you insert will be a sibling of the currently selected widget. Perhaps you've noticed that if you select a button or label, inserting point is parent of the widget (usually a frame or toplevel). "Set Insert" entry overrides this, e.g. if you want to put a button on top of another button. Probably this is the only use, Grzegorz Popiela <> says.

[ I find this of dubious utility... Any other use? ]

How can I create compound objects? I appreciate the system compound "Label and Entry" and I would like to add my own ones.

Grzegorz Popiela <> again advises:

Just select a frame with some widgets in it and choose Compound->Create. You will be asked for the compound name. Lets call it "myCompound". To reuse that compound widget again, just select the place where you want to insert it, and choose menu->Compound->Insert->user->myCompound.

If you want to use "myCompound" in other projects, just choose Menu->Compound->Save Compounds, and specify a file name. Later, on other projects, just choose Menu->Compound->Load Compounds. Voila, code reusability!

Additionally, there are functions associated with compound widgets:

If procedure "myCompound:init" is defined before the compound is created, the next time you insert it the procedure will be executed before the compound widget is created. You may e.g. create images there.

If procedure "myCompound:main" was defined, it will be executed after the widgets are created. It may be used to insert some data into newly created widgets of compound, or set up links between them.

Other procedures (myCompound:*) will also become a part of the compound.

[ Is there a standard interface to them, as with "main" and "init" ? ]

Is there a work around for this error? I am using the placer geometry
        Error in startup script: can't use placer on top-level
        window "."; use wm command instead

Greg Anderson <> says:

When you get this error, replace the sections "CREATING WIDGETS" and "SETTING GEOMETRY" in the proc vTclWindow with the template below, and the error will disappear.

  • Delete the "place command" from the "SETTING GEOMETRY" section.
  • Add wm code to the "CREATING WIDGETS" section to create and then hide the top window.  Keep a template file, like the one below, to copy into the "CREATING WIDGETS" section.

The vTclWindow proc creates  and then hides the main window, so I don't think the definitions for geometry, maxsize, minsize, etc. are that important.

When the error occurs, you will notice that in the proc vTclWindow, the "CREATING WIDGETS" section is missing the wm code and the "SETTING GEOMETRY" section has a "place" command in it.

Here's a template you can use to quickly fix this error:

proc vTclWindow. {base} {
    if {$base == ""} {
        set base .
    wm focusmodel $base passive
    wm geometry $base 1x1+0+0
    wm maxsize $base 1265 994
    wm minsize $base 1 1
    wm overrideredirect $base 0
    wm resizable $base 1 1
    wm withdraw $base
    wm title $base "Whatever"

Why, after finishing my application and running it on another Xserver, all fonts are wrong, destroying my carefully designed layout?

A possible answer: If you specify fonts only partially, such as Helvetica-*-12-*-*..., the Xserver picks the first one that fits. Another Xserver may have a different set of fonts, and the one that first fits the specification is different, with  unpredictable results.

On the other side, if you specify a font completely, and the Xserver can't find it, Tk may die, or the nearest font matched is really very different than the one that you intend.

Another frequent error is to specify fonts with pixel size, not point size, and of course if you change from a 70 dpi to a 100 dpi monitor, than your application will be shrinked.

Another frequent error is related with an improper setup of the font path for the Xserver (run `xset q'). If you specify your font with an "*" in the x or y dpi sizes, again the Xserver will pick the first one it found. If you are using a 100dpi monitor, but the font path for the xserver list first the directories of the 75dpi fonts, you are in trouble.

With tk, fonts can, and should be, specified in a different way: use "Helvetica 12" to specify a 12 points helvetica font, and "Helvetica - 12" to specify 12 pixel--discouraged (run `man font n')

Can I use the placer only with relative positions? I find annoying not to be able to resize my windows and keep the geometry.

[ Who knows? Is this a contest? :)]

How could I build a scrollable window like the attribute editor of Vtvl ? (I can't move widgets as buttons or labels with scrollbars)

I took the following approach using the packer:

  1. a frame
  2. a checkbutton inside and on top of it ("-side top -fill x")
  3. another frame bellow ("-fill x -side bottom")
  4. all other widgets inside that second frame.
  5. bind the following procedure to the checkbutton ("-command shrink_expand"):
proc {shrink_expand} {} {
        set but_path [winfo containing [winfo pointerx .] [winfo pointery .]]

        set parent_name [winfo parent $but_path]
        set children_name [winfo children $parent_name]

        if {[lsearch $children_name $but_path] == "0" } {
           set fra [lindex $children_name 1]} else { set fra [lindex $children_name

        upvar [$but_path cget -variable] var
        if { $var } {
            pack forget $fra} else {
            pack $fra -fill x}

I am wanting to know how to have a place to put functions that I might want to include in several apps. but I do not know what to do in tcl and then how to do it as well in vtcl?

Rick Macdonald <> has a solution: you should create a Tcl library with your functions (see a Tcl FAQ), then run the "auto_mkindex" command and then add your library directory to the auto_path:

        lappend auto_path /usr/local/lib/MyTcl

where /usr/local/lib/MyTcl is the directory where your Tcl library is.

The problem is that when you load the application into vTcl, it will save these functions into the application, and you don't want that. To avoid it, just add

    append vTcl(proc,ignore) "|mylib_*"

This assumes that all the procs that you source in start with the string "mylib_". You could add the above line at the bottom of your "init" function. However, each time that vTcl runs your init function the vTcl(proc,ignore) value will get longer and longer.

Mitchell Roe <>, for example, adds the following lines at the bottom of it's init function, and although vTcl(proc,ignore) really grows it causes no problems to him:

        global vTcl
        set id [open [file join $mylib tclIndex] r]
        foreach line [split [read $id] \n] {
            if {[regexp {set auto_index\(([^)]*)} $line match proc]} {
                append vTcl(proc,ignore) "|$proc"
        close id

Alternatively, you could add the following line into the vTcl "globals.tcl" source file. The vTcl default is to ignore procedures matching "tcl.*|tk.*|auto_.*|bgerror|\\..*":

        set vTcl(proc,ignore)    "tcl.*|tk.*|auto_.*|bgerror|\\..*"

The simplest solution however will be to always call your functions starting with the string "tcl". Then you don't even have to modify the vTcl ignore list.

How can I hide a frame and all widget on it? I would like to have multiple frames in one  window and hide or reveal them (and all the objects in the frame) when a user presses a button.

Rick Macdonald <> says: `pack forget <frame>' to hide and `pack <frame>' to reveal (if using the packer geometry manager). If it doesn't resize properly by itself try this before and/or after the various pack commands until it does:

     # Clear the geometry settings so the window resizes
     wm geometry $widget(your_toplevel) ""

If the packing order is important, i.e., you are hidding/revealing several frames, you may need

        pack $frame -after $other_frame

Otherwise, it's tricky to make sure the frame gets repacked in the right location.

With the grid geometry manager, use

        grid conf ....
        grid forget ...

Other possibility is to use the vTcl builtin procedure "Window":

        Window hide $windowname
        Window show $windowname

The advantage is that the "Window" proc will create the toplevel if it doesn't exist or deiconify it if it does. You don't need to keep track or worry about it.

How can I recursively disable all widgets inside a given frame? I don't want to just hide it, as the window geometry changes.

Rick Macdonald <> answers: Call the following function with the containing frame and everything is greyed out, disabled, etc. The only non-general thing I've done is that if a widget (such as entry) has a
green background, I leave it disabled.

Actually, I think this is really cool. I'm using it more and more.

proc {toggleDisabled} {state wtop disabledfg} {
    if {[winfo class $wtop] == "Frame"} {
        set children [winfo children $wtop]
    } {
        set children $wtop
    foreach w $children {
        if {[winfo class $w] == "Frame"} {
            toggleDisabled $state $w $disabledfg
        if {[lsearch -exact "Entry Label Message" [winfo class $w]] >= 0}
            if {$state == "disabled"} {
                $w config -foreground $disabledfg
            } {
                $w config -foreground black
        if {[lsearch -exact "Button Checkbutton Entry Radiobutton" [winfo
class $w]] >= 0} {
            if {$state == "disabled"} {
                $w config -state disabled
            } {
                if {[$w cget -background] != "green"} {
                    $w config -state normal

Get the disabled foreground from any handy button widget:

     set disabledcolour [$widget(auto_button) cget -disabledforeground]

"state" is disabled or normal, "wtop" is the containing frame.

Then disable and enable with these calls:

toggleDisabled disabled $widget(start_frame)    $disabledcolour
toggleDisabled normal   $widget(start_frame)    $disabledcolour

I am really new to this Tcl/Tk stuff in order to use vTcl properly. Where can I find a Tcl FAQ?

This one is really easy. The only problem is the amount of information... Try

I want to put an image on a button. How can I do that in vtcl?

In the "attribute editor" window there is a field named "image" where you should type the name of the image to put on the button. But you should create the image first. A good place is in the "init" function. Open the "function window" and double click on the function named "init"; then type in the function body:

image create photo nameoftheimage -file /directoryoftheimage/yourimage.gif

To put it in a label or button, etc. just insert "yourimage" in the image entry of the attribute editor, Guillaume Laisney <> said.

I can't understand the basic working of vtcl. Is a working demo available?

You should check vTcl WEB home page. There is an Introduction tcl-intro.html and a Tutorial tutorial.html>there. In the source distribution that you downloaded you will find also the tutorial at <distribution_home>/doc/tutorial.txt>

[Of course an animated or interactive demo would be the best--and it would
demonstrate also the WEB capabilities of Tcl. Any volunteers? Another nice
demo would be one like the one found in the xf GUI designer]

And online free books on Tcl/Tk?

You can find an old free book for personal use, Brent Welch's "Practical Programming in Tcl and Tk", which covers tcl/tk version 7.4/4.0 at The book has been meanwhile published by Prentice Hall (1st edition: ISBN 0-13-182007-9, 2nd edition: ISBN 0-13-616830-2).

You can also find another old book by John Ousterhout's, "Tcl and the Tk Toolkit", which has been meanwhile published by Addison-Wesley, ISBN 0-201-63337-X. The free book only cover tcl/tk version 7.3/3.6.

I'd like to...

Sorry, no such entry on the FAQ. Please send the query to the list, and I will collect the answers. You could help if, after solving your problem, send me the solution.

Besides this "FAQ", is there a mailing list? Is it archived somewhere?

The mailing list is currently archived at You can subscribe it at Tcl homepage. See next question.

Has vTcl a homepage? what is it's address? Where can I find vTcl sources for download?

The vTcl homepage is at You can find there all the relevant information such as download and install information, Tcl/Tk links, etc.

Besides vTcl are other free Tcl/Tk GUI development environments?

Yes. The most known are:

What is the difference between vtcl functions main and init?

The init() function is called before the creation of your widgets, immediately after the script starts and the creation of global variables. main() is called after the widgets creation.

Thus, when your script start, the order of execution is:

  1.    creation and setting of global variables
  2.    init() is called
  3.    the *visible* widgets are created (not the ones that are hidden)
  4.    main() is called

When you press the "Test" button the above sequence is also executed.

In vtcl where is the best place to put bindings? init? main? or my own functions?

The best way is to do it with the Options/Bindings (alt-b) menu option.

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