Tk::Button: How do I trigger a callback when button is pressed (as opposed to released)?

[perltux]

With Tk::Button the -command callback is invoked when the button is released. How do I additionally add a callback that gets invoked when the button is pressed?

Basically my aim is to make a sort of on-screen piano keyboard where pressing each Tk::Button widget with the mouse sends a MIDI 'note on' command and subsequently releasing the mouse button sends a MIDI 'note-off' command to a synthesizer.

[golux]

Hi perltux,

Use Button-1 for button-down events (as opposed to ButtonRelease-1 for button-up events). For example:

#!/usr/bin/perl -w

use strict;
use warnings;
use Tk;

my $mw  = new MainWindow(-title => 'Button press example');
my $bt  = $mw->Button(-bg => '#ffefb5', -text => 'Press Me');
my $txt = $mw->Text(-bg => 'white');
$bt->pack($txt);
$bt->bind('<Button-1>'        => sub { button_down($txt) });
$bt->bind('<ButtonRelease-1>' => sub { button_up($txt) });
Tk::MainLoop;


sub button_down {
    my ($text) = @_;
    my $time = localtime(time());
    $text->insert("end", "$time:  Button Down\n");
}


sub button_up {
    my ($text) = @_;
    my $time = localtime(time());
    $text->insert("end", "$time:  Button Up\n");
}

[perltux]

Thanks, that works great!

[Anonymous Monk]

Tk::bind

[perltux]

Thanks, I did actually look at bindings but I couldn't figure out how to use them for this situation. An example code snippet for this specific situation would be most appreciated.

[Anonymous Monk]

See Perl documentation documentation, Searching Perl Documentation, How to Read Perldocs

 [ddg://site:perlmonks.org Tk Button bind], [tk bind button] site:perlmonks.org Tk Button bind, tk bind button -> How can I un-bind a button in Perl Tk

$ perldoc -l -m Tk
C:\citrusperl\vendor\lib\Tk.pm

$ ack -hi ">bind.*button" C:\citrusperl\vendor\lib\Tk |tail
 $mw->bind($class,'<Control-ButtonRelease-1>','Control_ButtonRelease_1
+');
 $mw->bind($class,'<ButtonRelease-1>','ButtonRelease_1');
 $mw->bind($class,'<B1-Motion>',[ 'Button1Motion' ] );
 $mw->bind($class,'<Double-ButtonPress-1>',['Double1']);
 $mw->bind($class,'<Control-ButtonPress-1>',['CtrlButton1']);
 $mw->bind($class,'<Control-Double-ButtonPress-1>',['CtrlButton1']);
    $e->bind('<ButtonRelease-1>' => sub {
    $e->bind('<ButtonRelease-1>' => undef);
 $mw->bind($class,'<Button-6>',     ['xview','scroll',-1,'units']);
 $mw->bind($class,'<Button-7>',     ['xview','scroll',1,'units']);

$ which -a widget
C:/citrusperl/vendor/bin/widget
C:/citrusperl/vendor/bin/widget.BAT

$ head C:/citrusperl/vendor/bin/widget
#!/usr/bin/perl

use 5.008;
use Config;
use Tk 804.000;
use lib Tk->findINC( 'demos/widget_lib' );
use Tk::widgets qw/ DialogBox ErrorDialog LabEntry ROText /;
use Tk::Config ();
use WidgetDemo;
use subs qw/

perl Tk help, RFC: Learning Perl/Tk, Perl/Tk: For Beginners, Re^3: Tkx Search for dialog box for text input , Re: TclTk interface with Perl code, is it possible? , Re^2: GUI toolkit+designer for the perl newbie , Re: Easier GUI, Re: Should I use Perl/TK?, Re^2: need a popup gui stdin, Tk Tree Tutorial ( http://www.rtapo.com/tutorials/tk_tree.html ), some Tkx tutorial links, Tutorial http://theoryx5.uwinnipeg.ca/perltk/ and http://www.perl.com/pub/1999/10/perltk/, http://perltk.org/, http://web.archive.org/web/20100310202528/http://theoryx5.uwinnipeg.ca/perltk/

Leverage all available resources :)