Re:Text with transparent background

["Dirk van der Walt" <vrygesel highveldmail co za>]

Hi, 
Muppet, thank you for pointing me in the right direction. 
I know now a little more on the GDK gray area.

I wanted a ?or something
like OSD text, which shows only the text and no background
at all??


Included is what I ended up with. Its just a pity that the 
"$pixbuf = $pixbuf->add_alpha (TRUE, 0, 0 , 0);"

does not take out all of the background.

Hope this may help someone who want to do similar tricks

Comments welcome

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#!/usr/bin/perl -w

use strict;
use Glib qw/TRUE FALSE/;
use Gtk2 '-init';

#add a timer to run each second
Glib::Timeout->add (1000,\&new_screen);


#create a popup window -> this allow us th modify its size
to 
#that of a Gtk::Gdk::Pixmap class.
my $window= Gtk2::Window->new('popup');
	
	#standard packing widget
	my $vbox = Gtk2::VBox->new(FALSE,0);

		#create a image containing nothing, this will be set each
time 
		#the &new_screen sub runs
		my $img = Gtk2::Image->new_from_pixmap (undef, undef);
	
	$vbox->pack_start($img,FALSE,FALSE,0);
	
$window->add($vbox);

$window->set_position('center-always');
#show all BEFORE we add $drawing_area - we do not want to
show the drawing
#area, we only use it as a working surface.
$window->show_all();

	#Create a drawing area, and set is big enough to hold the
maximum size our 
	#text will ever be.
	my $drawing_area = Gtk2::DrawingArea->new;
	$drawing_area->set_size_request (1600, 1600);
	$vbox->pack_start($drawing_area,FALSE,FALSE,0);
	
	#realize it, since it will not be displayed, but we need
to 
	#get hold of the Gdk classes that needs it to be shown, or
realized
	$drawing_area->realize;
		#create a new pango layout for this drawing area
		my $pango_layout =
$drawing_area->create_pango_layout("");
		#get the defalt colormap (will be needed later on)
		my $colormap = Gtk2::Gdk::Colormap->get_system;
	#initial paint of screen
	&new_screen;
Gtk2->main;
	
sub new_screen {

	#this sub will get a new value of text, and display it on
the screen in a shaped 
	#window, to get there needs a few steps

	#get the text that we want to display on the screen.
	my $ts = ret_time();
	
	#Set our pango layout, to reflect the text and format that
we want.
	#NOTE We delebritely set the background to a certain color
to convert 
	#that color to a alpha channel, that will give us the
"clear" background. 
	$pango_layout->set_markup("<span background = '#000000'
foreground = '#FF0000' size = '20000' weight ='heavy'>Exact
time: </span><span background = '#000000' foreground=
'#00FF00' size='30000' weight =
'ultralight'><i><u>$ts</u></i></span>");
	
	#Get the size of this layout after the text was set.
	my($pango_w,$pango_h)=$pango_layout->get_pixel_size;
	
	#Now we have the size, we can create a pixmap that will be
the
	#'Gtk2::Gdk::Drawable' that we will draw upon
	my $pixmap = Gtk2::Gdk::Pixmap->new
($drawing_area->window,
                                    $pango_w,
                                    $pango_h,
                                    -1);
	#draw the pango layout on the drawable.
	$pixmap->draw_layout($drawing_area->style->black_gc,0,0,$pango_layout);
	
	#create a Gtk2::Gdk::Pixbuf that we will use to grab the
pango text from the
	#drawable (Gtk2::Gdk::Pixmap which is a
Gtk2::Gdk::Drawable) 
	my $pixbuf = Gtk2::Gdk::Pixbuf->new ('rgb', TRUE, 8,
$pango_w, $pango_h);
	
	#here we get create a pixbuff from the drawable, this is
where we need the colormap
	$pixbuf->get_from_drawable ($pixmap, $colormap, 0, 0, 0,0,
$pango_w, $pango_h);
		
		#Remove the background (we use a the color we specified
as the pango text's
		#background
		$pixbuf = $pixbuf->add_alpha (TRUE, 0, 0 , 0);
		
		#create a pixmap and mask from the Gtk2::Gdk::Pixbuf
		my ($pm, $m) = $pixbuf->render_pixmap_and_mask (255);
	#shrink our window to make sure the mask and pixmap will
be on the same spot.
	$window->resize(4,4);
	#replace the old $img with the new pixmap and mask
	$img->set_from_pixmap ($pm, $m);
	
	#shape our window accordingly
  	$window->shape_combine_mask ($m, 0, 0);
  	
	return 1;
	
}


sub ret_time {
	#sub to return a string containing the time
my($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst)=
localtime(time+3600);
  	my @lst =("Sun","Mon","Tue","Wed","Thu","Fri","Sat");
  	my $thisday =$lst[$wday];
  	$year = $year + 1900;
  
  	($sec =~ m/\d{2}/)||($sec = "0".$sec);
  	($min =~ m/\d{2}/)||($min = "0".$min);
  	($hour =~ m/\d{2}/)||($hour = "0".$hour);
  	$mon = $mon +1;
  	#print("\n");
  	my $ts = "$thisday $mday/$mon/$year $hour:$min:$sec";
	
	return $ts;
}

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