How can I catch a `shift`-`key` combination with Win32::Console::Input?

Question

How can I catch a shift-some-key combination with this script?
When I press the Arrow-keys I get what I expect, but when I press shift-tab it doesn't return the KEY_BTAB value.

use warnings;
use 5.12.0;
use Win32::Console qw(STD_INPUT_HANDLE ENABLE_MOUSE_INPUT);
use constant {
    RIGHT_ALT_PRESSED  => 0x0001,
    LEFT_ALT_PRESSED   => 0x0002,
    RIGHT_CTRL_PRESSED => 0x0004,
    LEFT_CTRL_PRESSED  => 0x0008,
    SHIFT_PRESSED      => 0x0010,

    VK_LEFT     => 0x25,
    VK_UP       => 0x26,    
    VK_RIGHT    => 0x27,    
    VK_DOWN     => 0x28,    
    VK_TAB      => 0x09,    
};
use constant SHIFTED_MASK =>
    RIGHT_ALT_PRESSED |
    LEFT_ALT_PRESSED |
    RIGHT_CTRL_PRESSED |
    LEFT_CTRL_PRESSED |
    SHIFT_PRESSED;

my %d = (
    KEY_DOWN            => 258,
    KEY_UP              => 259,
    KEY_LEFT            => 260,
    KEY_RIGHT           => 261,
    KEY_BTAB            => 353,
);

my $con_in = Win32::Console->new(STD_INPUT_HANDLE);
$con_in->Mode(ENABLE_MOUSE_INPUT);

while ( 1 ) {
        my $key = getch();
        say "<$key>";
        last if $key == 113;
}

sub getch {
    my @event = $con_in->Input();
    my $event_type = shift( @event );
    if ( defined $event_type and $event_type == 1 ) { 
        my ( $key_down, $repeat_c, $vkcode, $vsccode, $char, $ctrl_ks ) = @event;
        if ( $char ) {
            return $char;
        }
        else {
            if ( $vkcode == VK_UP and ( $ctrl_ks & SHIFTED_MASK ) == 0 ) {
                return $d{KEY_UP};
            }
            elsif ( $vkcode == VK_DOWN and ( $ctrl_ks & SHIFTED_MASK ) == 0 ) {
                return $d{KEY_DOWN};
            }  
            elsif ( $vkcode == VK_RIGHT and ( $ctrl_ks & SHIFTED_MASK ) == 0 ) {
                return $d{KEY_RIGHT};
            }        
            elsif ( $vkcode == VK_LEFT and ( $ctrl_ks & SHIFTED_MASK ) == 0 ) {
                return $d{KEY_LEFT};
            } 
            elsif ( $vkcode == VK_TAB and $ctrl_ks == SHIFT_PRESSED ) {
                return $d{KEY_BTAB};    # <--
            }
            else {
                say "beep";
            }
        }
    }
}

Output when I press shift and tab:
beep
<1>
<9>
<9>
beep
<1>

After editing the getch routine this way

sub getch {
    my @event = $con_in->Input();
    my $event_type = shift( @event );
    if ( defined $event_type and $event_type == 1 ) { 
        my ( $key_down, $repeat_count, $virtual_keycode, $virtual_scancode, $char, $ctrl_key_state ) = @event;
        if ( $char ) {
            if ( $key_down ) {
                return $char for $repeat_count;
            }
        }
        else {
            if ( $virtual_keycode == VK_UP and ( $ctrl_key_state & SHIFTED_MASK ) == 0 ) {
                if ( $key_down ) {
                    return $d{KEY_UP} for $repeat_count;
                } 
            }
            elsif ( $virtual_keycode == VK_DOWN and ( $ctrl_key_state & SHIFTED_MASK ) == 0 ) {
                if ( $key_down ) {          
                    return $d{KEY_DOWN} for $repeat_count;
                }
            }  
            elsif ( $virtual_keycode == VK_RIGHT and ( $ctrl_key_state & SHIFTED_MASK ) == 0 ) {
                if ( $key_down ) {
                    return $d{KEY_RIGHT} for $repeat_count;
                }
            }        
            elsif ( $virtual_keycode == VK_LEFT and ( $ctrl_key_state & SHIFTED_MASK ) == 0 ) {
                if ( $key_down ) {
                    return $d{KEY_LEFT} for $repeat_count;
                }
            } 
            elsif ( $virtual_keycode == VK_TAB and ( $ctrl_key_state & SHIFTED_MASK ) == SHIFT_PRESSED ) {
                if ( $key_down ) {
                    return $d{KEY_BTAB} for $repeat_count;
                }
            }
            else {
                say "beep";
            }
        }
    }
}

I get this output:
beep
<1>
<9>
<0>
beep
<1>

ikegami · Accepted Answer

Firstly, $char is set to 9, so you never get to your check. Move the if ($char) check to somewhere more appropriate.

Secondly, your check is wrong. The following won't work if, say, Caps Lock is on.

elsif ( $vkcode == VK_TAB and $ctrl_ks == SHIFT_PRESSED )

You should only check the flags you are interested in.

elsif ($vkcode==VK_TAB and ( $ctrl_ks & SHIFTED_MASK ) == SHIFT_PRESSED)

Finally, sometimes you only get notified once for multiple presses. That is signaled by $repeat_count. You ignore this, so you potentially ignore keys.

You try to handle $repeat_count in the second snippet, but fail miserably. Part of the problem is you copied for $repeat_count from my other answer when it should be for 1..$repeat_count, and the other problem is that you only return one value even if $repeat_count is larger than one.

my @kbd_queue;
sub getch {
    my @event;
    if (@kbd_queue) {
       @event = ( 1, @{ pop @kbd_queue } );
    } else {
       @event = $con_in->Input();
    }

    my $event_type = shift( @event );
    if ( defined $event_type and $event_type == 1 ) { 
        my ( $key_down, $repeat_count, $virtual_keycode, $virtual_scancode, $char, $ctrl_key_state ) = @event;
        return -1 if !$key_down;

        if ( $virtual_keycode == VK_UP and ( $ctrl_key_state & SHIFTED_MASK ) == 0 ) {
            push @kbd_queue, \@event for 2..$repeat_count;
            return $d{KEY_UP};
        } 
        ...
        elsif ( $virtual_keycode == VK_TAB and ( $ctrl_key_state & SHIFTED_MASK ) == SHIFT_PRESSED ) {
            push @kbd_queue, \@event for 2..$repeat_count;
            return $d{KEY_BTAB};
        }
        elsif ( $char ) {
            push @kbd_queue, \@event for 2..$repeat_count;
            return $char;
        }
        else {
            say "beep";
        }
    }
}

You should convert this into something table-driven.

How can I catch a `shift`-`key` combination with Win32::Console::Input?

Answers (2)

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