Overlay

After Asciio draws the elements, a user defined call back is called.

User defined callback

The callback receives an instance of Asciio as the first argument, you can use that instance to get elements, ...

The callback return a list of 1character overlay in array references:

• x coordinate
• y coordinate
• character
• optional background color
• optional foreground color

Example list:

[ 0, 0, 'T'],
[ 1, 0, 'e'],
[ 2, 0, 's'],
[ 3, 0, 't'],

Setting and resetting the callback

The callback is set by calling $asciio->set_overlays_sub. The simplest is to do it via a key binding.

'set overlays' =>
	[
	'0A0-o',
	sub 
		{
		my ($asciio) = @_ ;
		
		$asciio->set_overlays_sub
			(
			sub { [0, 0, 'O'], [1, 0, 'K'] }
			) ;
		
		$asciio->update_display ;
		}
	],

Reset the callback

'reset overlays' => [ '000-o', sub { $_[0]->set_overlays_sub(undef) ; $_[0]->update_display ; } ],

Callback access to canvas

The callback can also have access to the canvas, but don't

Arguments:

• $asciio
• $UI_type, set to GUI/TUI
• $gc
• $widget_width
• $widget_height
• $character_width
• $character_height

Example: draw and overlay and a filled rectangle above the mouse pointer

sub click_element_overlay
{
my ($asciio, $UI_type, $gc, $widget_width, $widget_height, $character_width, $character_height) = @_ ;

# draw directly
if($UI_type eq 'GUI')
	{
	my $surface = Cairo::ImageSurface->create('argb32', 50, 50) ;
	my $gco = Cairo::Context->create($surface) ;
	
	my $background_color = $asciio->get_color('cross_filler_background') ;
	$gco->set_source_rgb(@$background_color) ;
	
	$gco->rectangle(0, 0, $character_width, $character_height) ;
	$gco->fill() ;
	
	$gc->set_source_surface($surface, ($asciio->{MOUSE_X} - 1 ) * $character_width, ($asciio->{MOUSE_Y} - 1) * $character_height);
	$gc->paint() ; 
	}

# send a list of characters to draw
my @overlays = map { [ $asciio->{MOUSE_X} + $_->[0], $asciio->{MOUSE_Y} + $_->[1], $_->[2] ] } @$click_element_overlay ;

@overlays
}

Callback hide/show mouse

Hide and show the mouse pointer, useful if you draw objects that are moved around.

sub callback_enter { my ($asciio) = @_ ; $asciio->hide_cursor ; ... }

sub callback_escape { my ($asciio) = @_ ; $asciio->show_cursor ; ... }