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 ; ... }