I've made a cut-down example shown below.
If I click the Options button the Options dialog shows as it should.
And if I click the Options dialog's Close button it is hidden.
But if I click the Options button a second time I get the error:

bad window path name ".optionsForm"

Clearly I've made a mistake, but I don't know Tcl/Tk well enough to see
what I've done wrong.

#!/usr/bin/env wish9

package require tepam

tk scaling 1.67
tk appname HideShow

proc main {} {
wm withdraw .
wm title . [tk appname]
wm attributes . -type dialog
wm minsize . 200 200
make_widgets
wm deiconify .
raise .
}

namespace eval test {
variable optionsButton
variable optionsForm
}

proc make_widgets {} {
set test::optionsButton [ttk::button .optionsButton -text Options… \
-underline 0 -command test::on_options]
pack .optionsButton
bind . <Alt-o> {$test::::optionsButton invoke}
bind . <Escape> {destroy .}
}

# Hide/show dialog
proc test::on_options {} {
if {![info exists ::test::optionsForm]} {
puts "on_options init"
set ::test::optionsForm [toplevel .optionsForm]
wm title .optionsForm "Options — [tk appname]"
ttk::label .optionsForm.label -text "Options go here"
grid .optionsForm.label -row 0 -column 0
ttk::button .optionsForm.closeButton -text Close \
-command {destroy $::test::optionsForm}
grid .optionsForm.closeButton -row 1 -column 0
dialog prepare .optionsForm
wm protocol .optionsForm WM_DELETE_WINDOW \
{dialog hide $::test::optionsForm}
bind .optionsForm <Escape> {destroy $::test::optionsForm}
}
puts on_options
dialog show .optionsForm
}

namespace eval dialog {}

tepam::procedure {dialog prepare} {
-named_arguments_first 0
-args {
{-modeless -type none}
{-parent -default .}
{window}
}
} {
wm withdraw $window
wm attributes $window -type dialog
if {!$modeless} { wm transient $window $parent }
}

tepam::procedure {dialog show} {
-named_arguments_first 0
-args {
{-modeless -type none}
{-focuswidget -default ""}
{window}
}
} {
puts "dialog show $window"
wm deiconify $window
raise $window
focus $window
if {$focuswidget ne ""} {focus $focuswidget}
if {!$modeless} {
catch {grab set $window}
catch {tkwait visibility $window}
}
}

tepam::procedure {dialog hide} {
-args { {window} }
} {
wm withdraw $window
grab release $window
}

main

* Mark Summerfield <mark@qtrac.eu>
| I've made a cut-down example shown below.
| If I click the Options button the Options dialog shows as it should.
| And if I click the Options dialog's Close button it is hidden.

No, it's not, it is destroyed (as you requested by)

| ttk::button .optionsForm.closeButton -text Close \
| -command {destroy $::test::optionsForm}

Part of the problem is that you only check for the existence of the
variable, but not of the window it describes. The second time you call
test::on_options, the variable exists, but the window does not since it
was destroyed by the closeButton.

| # Hide/show dialog
| proc test::on_options {} {
| if {![info exists ::test::optionsForm]} {

I suggest to add
|| ![winfo exists $::test::optionsForm]

in test::on_options (and probably to unify all the different ways to
withdraw/destroy the window - Close button, WM_DELETE, Escape).

HTH
R'

On Wed, 26 Jun 2024 12:23:13 +0200, Ralf Fassel wrote:

> * Mark Summerfield <mark@qtrac.eu>
> | I've made a cut-down example shown below.
> | If I click the Options button the Options dialog shows as it should. |
> And if I click the Options dialog's Close button it is hidden.
>
> No, it's not, it is destroyed (as you requested by)
>
> | ttk::button .optionsForm.closeButton -text Close \
> | -command {destroy $::test::optionsForm}
>
> Part of the problem is that you only check for the existence of the
> variable, but not of the window it describes. The second time you call
> test::on_options, the variable exists, but the window does not since it
> was destroyed by the closeButton.
>
> | # Hide/show dialog | proc test::on_options {} {
> | if {![info exists ::test::optionsForm]} {
>
> I suggest to add
> || ![winfo exists $::test::optionsForm]
>
> in test::on_options (and probably to unify all the different ways to
> withdraw/destroy the window - Close button, WM_DELETE, Escape).
>
> HTH R'

You are quite right, I made a silly copy/paste mistake.

I now use a lambda:

set on_close [lambda {} {dialog hide .optionsForm}]

and set this and the close button's command, the wm protocol for delete
window and for Esc.

I have not added the or-clause you suggested since my view is that if the
variable exists and the window doesn't it is a coding error and I want the
exception.

Thanks for your help.

[snip]

Based on your idea of using winfo exists I've now refined the on_options
proc to this:

proc test::on_options {} {
if {![winfo exists .optionsForm]} {
puts "on_options init"
toplevel .optionsForm
set on_close [lambda {} {dialog hide .optionsForm}]
wm title .optionsForm "Options — [tk appname]"
ttk::label .optionsForm.label -text "Options go here"
grid .optionsForm.label -row 0 -column 0
ttk::button .optionsForm.closeButton -text Close -command
$on_close
grid .optionsForm.closeButton -row 1 -column 0
wm protocol .optionsForm WM_DELETE_WINDOW $on_close
bind .optionsForm <Escape> $on_close
dialog prepare .optionsForm
}
puts on_options
dialog show .optionsForm
}

* Mark Summerfield <mark@qtrac.eu>
| proc test::on_options {} {
| if {![winfo exists .optionsForm]} {
| puts "on_options init"
| toplevel .optionsForm
| set on_close [lambda {} {dialog hide .optionsForm}]
| wm title .optionsForm "Options — [tk appname]"
--<snip-snip>--

I make a habit of putting the layout of any widget structure in
variables, so if I decide to add another frame or toplevel or whatever,
I just need to change the variables and leave the rest of the code
unchanged:

proc test::on_options {} {
set w(optionsForm) .optionsForm
set w(optionsLabel) $w(optionsForm).label
set w(optionsClose) $w(optionsForm).closeButton
if {![winfo exists $w(optionsForm)]} {
puts "on_options init"
toplevel $w(optionsForm)
set on_close [lambda {} [list dialog hide $w(optionsForm)]]
wm title $w(optionsForm) "Options — [tk appname]"

ttk::label $w(optionsLabel) -text "Options go here"
grid $w(optionsLabel) -row 0 -column 0
ttk::button $w(optionsClose) -text Close -command $on_close
grid $w(optionsClose) -row 1 -column 0
...

Say I need the options frame as child of a different widget than ".",
I could just change the proc to

proc test::on_options {top} {
set w(optionsForm) $top.optionsForm
...

and be done.

HTH
R'