My app runs under Windows, Linux and macOS.
Two menu bar entries have the accelerators Control-Up/Down, resp. Command-Up/Down under macOS.
Others have other accelerators, e.g. Control-A/B, resp. Command-A/B under macOS.

When I select one of the four menu entry, the command is called once under all three OSs.
When I press Command-Up/Down on the keyboard under macOS, the command is called *twice*.
This is *not* the case for the other keyboard bindings Command-A/B.

What's the difference with Command-Up/Down bindings under macOS?

The following code demonstrates the behaviour:

- - - - - - - - - -
package require Tk

if {[tk windowingsystem] eq "aqua"} {
set APPDATA(control) "Command"
} else {
set APPDATA(control) "Control"
}

proc do_cmd {} {
puts "do_cmd"
}

menu .mbar
.. configure -menu .mbar
menu .mbar.mm -tearoff 0
..mbar.mm add command -label Up -accelerator $APPDATA(control)-Up -command do_cmd
..mbar.mm add command -label Down -accelerator $APPDATA(control)-Down -command do_cmd
..mbar.mm add command -label A -accelerator $APPDATA(control)-A -command do_cmd
..mbar.mm add command -label B -accelerator $APPDATA(control)-B -command do_cmd
..mbar add cascade -label MyMenu -menu .mbar.mm

bind . <$APPDATA(control)-Up> "do_cmd"
bind . <$APPDATA(control)-Down> "do_cmd"
bind . <$APPDATA(control)-a> "do_cmd"
bind . <$APPDATA(control)-b> "do_cmd"

On 10/12/22 5:58 PM, Torsten wrote:
>
> When I select one of the four menu entry, the command is called once
> under all three OSs.
> When I press Command-Up/Down on the keyboard under macOS, the command is
> called *twice*.
> This is *not* the case for the other keyboard bindings Command-A/B.
>
> What's the difference with Command-Up/Down bindings under macOS?
>

Just a guess but it sounds like there may be additional bindings for
those keys. What do you see if you run the following commands?

bind . <$APPDATA(control)-Up>
bind . <$APPDATA(control)-Down>